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First Impression: 2014 © NITTTR, Chandigarh International Conference on Recent Advances and Trends in Electrical Engineering (RATEE-2014) ISBN: 978-93-84869-05-2 No part of this publication may be reproduced or transmitted in any form by any means, electronic or mechanical, including photocopy, recording, or any information storage and retrieval system, without permission in writing from the copyright owners. DISCLAIMER The authors are solely responsible for the contents of the papers compiled in this volume. The publishers or editors do not take any responsibility for the same in any manner. Errors, if any, are purely unintentional and readers are requested to communicate such errors to the editors or publishers to avoid discrepancies in future. Published by EXCEL INDIA PUBLISHERS 91 A, Ground Floor Pratik Market, Munirka, New Delhi–110067 Tel: +91-11-2671 1755/ 2755/ 3755/ 5755 Fax: +91-11-2671 6755 E-mail: [email protected] Web: www.groupexcelindia.com Typeset by Excel Publishing Services, New Delhi–110067 E-mail: [email protected] Printed by Excel Printing Universe, New Delhi–110067 E-mail: [email protected]

Preface The progress of any country is judged by the index as to how much electrical energy it is generating and utilizing. The demand of electrical energy in our country is increasing at a very fast rate and this necessitates the need to generate more power .Thus the role of electrical engineer becomes all the more important in today’s scenario. Per capita Electrical Energy Consumption is an index of the standard of living of a country and its industrial and economic potential. It is a well known fact that our country is very badly lagging behind in this area. The realization has now dawned that if India were to achieve a sustained annual economic growth of around 10%, it would have to improve its infrastructure including power generation by a factor of at least two. The government has all the intention of doing it and power generation is now under sharp focus. Other than generating power, energy conservation, audit and application of energy efficient technology form an integral part of appropriate technology being used for the progress of any country. Simultaneously, the field of electronics is advancing in a big way and finds its application almost in every field, such as communications, power generation and management, automation, defence, consumer electronics, automobile engineering, control engineering, medical electronics and aerospace applications. There is a huge deficit in the demand and supply of well-qualified and trained Electrical and Electronics Engineers in the country. This makes it mandatory to probe the latest technology in the field of Electrical Engineering and train the engineers accordingly for the future. The editors hopefully feel that the research papers included in the proceedings shall create awareness and appreciation amongst academicians, scientists, researchers and practitioners from various disciplines and sectors about new ventures to be initiated towards understanding Recent Advances and Trends in Electrical Engineering and formulating concrete strategies with optimal utilization of available resources for developing appropriate technologies. Editors would like to express their deep felt thanks to the contributing authors and the publisher in bringing out the proceedings. Editors Dr. Lini Mathew Mrs. Shimi S.L. Mrs. Ritula Thakur

Organizing Committee Chief Patron Dr. M.P. Poonia Director, NITTTR, Chandigarh

Conference Chair Dr. S. Chatterji

Technical Program Chair Dr. Lini Mathew

Publication Chair Mrs. Shimi S.L. Mrs. Ritula Thakur

Treasurer Mr. Hans Raj Sharma Mr. Vinod Kumar Sharma

Session Management Dr. J.S. Saini Dr. S.S. Pattnaik Dr. B.S. Pabla Dr. S.S. Banwait Dr. Sanjay Sharma Dr. Maitreyee Dutta Dr. Hemant Sood Dr. S.S. Dhami Dr. C. Ramakrishna Prof. O.S. Khanna

Networking, Website Design and Management Mrs. Shimi S.L. Mr. Abinav Kant Mr. Pradeep Bansal

Registration Mrs. Ritula Thakur Mr. Vinod Kumar Sharma Mr. Mohan Lal Mr. Mahesha Nand Mr. Bhag Singh Mr. Arjun Singh

Inauguration, Valediction, Accomodation and Catering Dr. U.N. Roy Dr. (Mrs.) S.P. Bedi Mr. R.K. Goel Mr. Hans Raj Sharma Mr. Vinod Kumar Sharma

Publicity Dr. U.N. Roy Mr. Amardev Singh Mr. Amandeep Sharma Mr. Yogendra Narayan, Mr. Mohammad Junaid Khan Mr. Vanraj

Transport Dr. S.S. Dhami Mr. Hansraj Sharma

Electrical Maintenance Dr. Lini Mathew Mr. R.K. Goel Mr. Satish Kumar

Committees  ix

Secretarial Assistance Mrs. Malkeet Kaur Mrs. Jayanthi Mr. Bhag Singh

Photography/Video Recording/AV aids Coordination Dr. S.S. Pattnaik

Dr. Rakesh Wats Mr. K.S. Elias Mr. Dinesh Kumar Mr. Natwar Singh Mr. Sidharth Nanchahal Mr. Rajiv Negi Mr. Surinder Singh Mr. A. Kapila Mr. Anurag Soni Mr. Mubarak Hussain

Advisory Committees International Advisory Committee Dr. Arindam Ghosh

Queensland University, Australia

Dr. Chanan Singh

Professor, Texas, A&M University, Texas, USA

Dr. C.V. Kandala

NPRL, USDA, Dawson, USA

Dr. Naveen Puppala

Associate Professor, NMSU, Clovis, USA

Dr. Amit Jindal

Minnesota, Canada

National Advisory Committee Dr. Vinod Kumar

Professor, IIT Roorkee

Dr. S.N. Singh

Professor, IIT, BHU

Dr. D.T. Shahani

Professor, IIT, Delhi

Dr. R.A. Gupta

Professor, MNIT, Jaipur

Dr. A. Swarup

Professor, NIT Kurukshetra

Dr. Dinesh Chandra

Prof. & Head, MNNIT Allahabad

Dr. Surekha Bhanot

Professor, BITS Pilani

Dr. Girish Sahani

Director, IMTECH, Chandigarh

Dr. Amod Kumar

Scientist G, CSIO, Chandigarh

Dr. Renu Vig

Director, UIET, Chandigarh

Dr. Shiv Narayan

Professor , PEC University of Technology, Chandigarh

Dr. Smarajit Ghosh

Prof. & Head ,Thapar University, Patiala

Dr. J.S. Saini

Professor, NITTTR, Chandigarh

Dr. S.S. Pattnaik

Professor ,NIIITR, Chandigarh

Dr. B.S. Pabla

Professor ,NIIITR, Chandigarh

Dr. S.S. Banwait

Professor, NITTTR, Chandigarh

Contents Preface Messages Committees

v vi viii

TRACK I: POWER SYSTEMS & POWER ELECTRONICS 1. Power Blackouts: Causes and Preventive Measures in Context to Indian Blackouts Yajvender Pal Verma, Ishu Sethi, M.K. Sharma and Deepak Kumar

3

2. Design and Implementation of UPQC Model to Solve Power Quality Problems Amandeep Kaur and Lini Mathew

10

3. Virtual Laboratory for Tests on Transforme Neeraj Kumar, Rajesh Kumar and Lini Mathew

18

4. Design and Development of Power Quality Monitoring and Analysis System Based on LabVIEW Ajit Singh and Lini Mathew

23

5. Transformer Fault Diagnosis Based on DGA Method Using Classical Methods Pushpanjali Singh Bisht, Arrik Khanna and Deepak

29

6. Sustainable Electric Power Systems through PSDF Tanya Navin Kohli

34

7. Concept and Design of Nano Hydro Generator Abhinav Kant

40

8. Selection of a Custom Power Device for Power Quality Improvement Under Nonsinusoidal Conditions Tejinder Singh Saggu and Lakhwinder Singh

44

9. Design and Analysis of Grid-tied PV System Without Batteries: In Context to India Ranjay Kumar Ojha, Jayachandra Dama and Lini Mathew

49

10. A Review of High Power Cycloconverter Applications for Synchronous Motor Drives in Mining Industries Nikhil Ashok Bari and Jitendra R. Rana

55

11. FACTS Technology: An Overview Anjali Atul Bhandakkar

59

12. Exploiting Cloud Computing for Smart Grid Applications: A Review Aditya Bhardwaj, Maitreyee Dutta and Amit Doegar

66

13. Transmission Expansion Planning in Indian Context: A Review Raminder Kaur and Maneesh Kumar

71

14. High Frequency Modelling of Distribution Transformer Rohit Gupta, Mukesh Pathak and Ganesh Kumbhar

77

15. Modeling and Control of Micro-Grid Under Grid Connected and Disconnected Mode Manoj Chhimpa, S. Chatterji and Lini Mathew

83

16. A Fuzzy Relation Based Fault Diagnosis System for an Alternator Rajput H.K., Lini Mathew and Chatterji S.

89

17. Transmission Network Expansion Planning Using Genetic Algorithm Raminder Kaur and Tarlochan Kaur

94

18. Power Quality Problems: A Review Raminder Kaur and Gagandeep Singh

101

xii  Contents

TRACK II: PROCESS INSTRUMENTATION & CONTROL 19. Design and Performance Analysis of Fractional Order PID Controller for Power Converter M. Arounassalame

109

20. Simulation of Speed Control of Brushless DC Motor for Four Quadrant Operation B. Mahesh Kumar and S. Ragu

114

21. Load Frequency Control with Robust FOPID Controller Using PSO Ashu Ahuja, Shiv Narayan and Jagdish Kumar

119

22. A Novel Method for Moisture Determination in Peanuts Ritula Thakur, Babankumar S. Bansod, C.V.K. Kandala and S. Chatterji

123

23. Brain Emotional Learning Intelligent Controller Based Pitch Control of Helicopter Manoj Kumar Sharma and Anmol Kumar

126

24. Direct Torque Control of Induction Motor Simulation Using Conventional Method and Space Vector Pulse Width Modulation Naveen Chander, S. Chatterji and Lini Mathew

130

25. Design of Temperature Compensated pH Meter Ashutosh Gautam, S. Chatterji, Navdeep Kaur and Vikas Kumar

137

26. Fractional Order Based PID Control of Shell and Tube Heat Exchanger System Ravi Kant Sharma

140

27. Performance Enhancement of Sliding Mode Control: A Review Arpit Chugh and Sulata Bhandari

144

28. Liquid Level Control of Conical Tank Using Fractional Order PID Controller: State of Art Ritu Rajan, Vipul Agarwal and Priyanshi Vishnoi

148

29. On-line Monitoring of Water Quality Index Using LabVIEW—A Review Babankumar, Sudeshna, Pooja, Prashant Kumar, Danish Akhtar, S. Chatterji and Ritula Thakur

155

30. Software Sensor Pod for Real Time Potable Water Quality Monitoring Using Chemometrics Babankumar S. Bansod, Prashant Kumar, Pooja Devi, Sudeshna Bagchi, Nisarg Desai, Minesh Patel and Dhineshbabu L.D.

158

31. Designing of RF and Hypersepectral Imaging Based On-line Food Quality Analyser Babankumar S. Bansod, Shashwat Godhani, Revathi S. and Ritula Thakur

163

32. Arsenic Determination Techniques for Potable Water: A Review Pooja Devi, Babankumar, Manpreet Kaur, S. Chatterji and Ritula Thakur

167

TRACK III: BIOMEDICAL INSTRUMENTATION 33. Effect of Meditation on Heart Rate Dynamics Jitendra Kumar Jain, S.K. Bishnoi, Rajeev Gupta and Ranjan Maheshwari

173

34. Analysis and Review of Possible E-pill with Wireless Communication, Finding Applications in Biomedical Ajay Sharma, Ritula Thakur and Abhishek Kr. Mishra

177

35. Performance Analysis of Different Filters on ECG Noise Filtration: A Review Ankit Gupta and Sulata Bhandari

181

36. Haptic Feedback–A Review Alekh Manohar Sharma, Sanjeev Kumar and Amod Kumar

185

Contents  xiii

37. Unconventional Tasks and Challenges Faced by Big Data in Medical Science Gagandeep Jagdev, Baljeet Singh and Sawinder Pal Singh

190

38. Optical Pulse Oximetry–A Review Umesh Babu and Parveen Gupta

196

39. Sign Language Feature Extraction and Recognition Methods–A Review Sheenu

199

40. A Review of EEG and EMG-Based Control Approaches in Exoskeleton Robotic Arm Yogendra Narayan, Ram Murat Singh, S. Chatterji and Lini Mathew

203

41. Technologies for Representing Graphics for Visually Challenged Poonam Syal, S. Chatterji and H.K. Sardana

209

42. A Review on Brain Computer Interfacing Kitty Tripathi and Pushpender Sharma

216

TRACK-IV: RENEWABLE ENERGY SOURCES & ENERGY EFFICIENT TECHNOLOGY 43. Output Load Based Energy Efficient Solar Charge Sensor Design on 28nm FPGA Deepshikha Bhat, Amanpreet Kaur, Bishwajeet Pandey and Anu Singla

223

44. Techno-Economic Evaluation and Cost Benefit Analysis of Small Hydro Power Projects P.P. Sharma, S. Chatterji and Balwinder Singh

227

45. Energy Saving Analysis of Motors, Pumps and Air Compressors in Pulp and Paper Industry Mandeep Kaur Virk and Navneet Singh Bhangu

233

46. A Novel Fuzzy MPPT Controller for Extracting Maximum Energy from Solar Panel Swati Singh, S. Chatterji, Lini Mathew and Sandeep Gupta

237

47. Design and Simulation of Three-Phase Multilevel Inverter with Low Load Harmonics Contents and Less Switches Sandeep Gupta, Shimi S.L., S. Chatterji and Swati Singh

243

48. Simulation of Induction Generator and its Characteristics Related to Wind Power Applications Neha Kaushik and Supriya

249

49. Design of Photovoltaic Module with MATLAB/ SIMULINK Md. Manzar Nezami

254

50. Approximate Estimation of PV Performance Implemented on MATLAB/ SIMULINK Sayandev Ghosh, Prashant Kumar and Shimi S.L.

259

51. Modified Hybrid Wavelet-PSO-ANFIS Approach for Short-Term Electricity Prices Forecasting Mahesh S. Narkhede, S. Chatterji and Smarajit Ghosh

263

52. Energy Auditing of Industry—A Review Sanjay Kumar and Tilak Thakur

268

53. An Insight into Research Areas of DFIG Based Wind Generation Sunita Singh and Prerna Gaur

271

54. Energy Audit of an Official Building Prabjyot Singh and Tilak Thakur

277

55. A Survey of Various Maximum Power Point Tracking Techniques used in Solar Photovoltaic System Mohammad Junaid Khan, S. Chatterji, Lini Mathew and Amandeep Sharma

283

xiv  Contents

56. Emerging Trends in Energy Scavenging: A Review Saurabh Kumar and Loveleen Kaur Taneja

289

57. Modeling of Grid Integrated Photovoltaic Systems Rahul Nehra and Loveleen Kaur

295

58. Integration of Photovoltaic System with Smart Grid: A Review Sourav Diwania and Loveleen Kaur

300

59. An Overview of the Various Controller Techniques for DFIG-Based Wind Turbine System Maninder Pal Singh and Jaimala Gambhir

304

60. Challenges, Simulation and Analysis of Integrated Distributed Renewable Energy Sources Vinod Kumar Sharma, Mahesh S. Narkhede, Lini Mathews and S. Chatterji

310

61. An Overview of Modelling and Control Strategies for FRT Conditions in DFIG Based Wind Energy Systems Jaimala Gambhir and Tilak Thakur

314

TRACK V: EMBEDDED SYSTEM IN AUTOMATION 62. Intelligent Floating Car Parking Mehak Beri, Bharat Thakur and Kush Kulshrestha

323

63. Seasonal Weather Parameters Forecasting Using Soft Computing Techniques Monika Sharma

328

64. Self-Balancing Platform for Robot/ Machine Using Arduino Alok Deep and Jyoti Singh

333

65. Ultramodern Role of Artificial Neural Networks in Making Human Life Safe and Secure Gagandeep Jagdev and Kuldeep Singh

337

66. Smart Use of Microcontroller for the Management of Fecal Matter in Indian Railways Ankit Jain, Anita Shukla, Chanchal K. Vishwakarma and Lalat S. Nayak

342

67. An Intelligent Design to Detect Broken Track for Indian Railway Chanchal Kumar Viswakarma, Ankit Jain and Lalat Sankar Nayak

347

68. A Low Cost Water Supply Management for Urban Areas Using LabVIEW and Microcontroller Lalat Sankar Nayak, Ankit Jain and Chanchal Kumar Viswakarma

350

69. Design and Development of an Advanced Irrigation System Using GSM Technology Ajay K. Yadav, S. Chatterji and A.K. Singh

355

70. Study of Robotic Applications: Challenges and Future Aspects Priya Shukla, Pallavi Verma and Pooja Sharma

359

AUTHOR INDEX

365

TRACK–I POWER SYSTEMS & POWER ELECTRONICS

Power Blackouts: Causes and Preventive Measures in Context to Indian Blackouts Yajvender Pal Verma

Ishu Sethi

(EEE) U.I.E.T., Panjab University, Chandigarh, India e-mail: [email protected]


M.K. Sharma

Deepak Kumar



Abstract—There has been a long history of power blackouts. These are unplanned short term or long-term power outages, which can affect millions of people, and no single factor is responsible for them. The sequences of events, which can lead to blackouts, are initiation of disturbance, cascade tripping of transmission lines and generation-load imbalance. The main reasons behind such power outages are system congestion, unwanted operation of distance relays due to load encroachment and power swings. In this paper, we have explored major technical reasons behind the blackouts and their preventive measures with main focus on the Indian blackouts. Our study shows the causes and loopholes that can lead to blackouts and further we have suggested preventive measures that can make the electrical system more immune to blackouts. Keywords: Blackouts, power system, load encroachment, power swing, cascade tripping.

I.

INTRODUCTION

Blackouts are power outages that are not planned by the electricity provider. There are many factors that can lead to blackouts like overloading of transmission lines, false operation of relays, power station fires, short circuits, and natural calamities etc. Such power outages can affect millions of people for many hours. Severe blackouts are inevitable owing to complex power system structure, varied nature of generating sources and uncertain load pattern [1]. Therefore, it is better to develop strategies for sufficient survival measures in such situations rather than eliminating blackouts [2]. Power system is the electrical infrastructure where electricity is generated, transmitted over long distances and finally distributed to the consumers. Several power systems are coupled together to form an electrical grid. In an electrical grid, power can be exchanged between different load centers. If some of the transmission lines are down for power transfer, alternative paths for electricity are available which helps in uninterrupted power supply. The coupling between power systems increases the reliability of the system as the power imbalances can be handled easily. But, it increases their vulnerability to random failures as the loss of a major transmission line or generator can lead to cascade of events, which may ultimately result in a blackout [3][4].

The electrical infrastructure is so vast and expanded that it is a challenge to form a system that is completely immune to blackouts. To make power systems more reliable and blackout resistant, it is very important to understand the main reasons and causes of blackouts. In this paper, an attempt has been made to investigate the main reasons and causes behind the blackouts with main focus on the Indian blackouts. Further, the possible solutions to avoid such catastrophic situations have been suggested. The rest of the paper is structured as: Section 2 highlight the major blackouts in the world, followed by the overview of Indian Power System and Blackouts in India in Section 3. Section 4 presents the technical analysis of the Blackouts; Section 5 gives the preventive measures followed by the discussion in Section 6.

II.

MAJOR POWER BLACKOUTS IN THE WORLD

There have been efforts to improve the performance of the power system and different countries worldwide have also initiated many reforms like deregulation of electricity system, introduction of smart grid etc. Despite these sincere efforts, there is a long history of blackouts. A few of them have been mentioned in Table I listing their major causes and the countries in which they took place. This section discusses few blackouts, which occurred due to different reasons such as natural calamity, equipment failures and network congestion.

A. 1989: Quebec Blackout [7] [8] Earth was struck by a geomagnetic storm on 13thMarch1989. It resulted in a blackout in Quebec because of its geographical location. Instead of flowing through the ground, the geo magnetically induced currents flowed through a less resistive path across the transmission lines. It resulted in tripping of transmission lines due to operation of over current relays. The entire system collapsed in 90 sec affecting nearly 6 million people.

4  International Conference on Recent Advances and Trends in Electrical Engineering (RATEE-2014)

B. 2003:Northeast (USA) Blackout of [13] [14] The northeastern blackout affected approximately 50 million people in eight states of USA and two Canadian

provinces. The sequence of events that led to blackout is shown in Fig. 1.

TABLE 1: MAJOR BLACKOUTS IN THE WORLD People Affected 30 million 6 million 97 million 226 million 50 million

Date of Blackout 9th Nov 1965 13th March 1989 11th March 1999 2nd January 2001 14th August 2003

60 million

28th September 2003

100 million 70 million 300 million 620 million

18th August 2005 10th Nov 2009 30th July 2012 31th July 2012

Causes Lack of monitoring and Inadequate system understanding Geomagnetic storm Chain reaction due to lightening strike at a sub station Insulation flashover and Aging equipment Equipment failure, lack of maintenance and ineffective communication Flashover due to tree and Loss of interconnection with rest of European electrical grid Aging equipment Insulator malfunction due to adverse weather conditions System congestion and depleted transmission network System congestion and depleted transmission network

Country USA Canada Brazil India USA and Canada

Reference [5] [6] [7] [8] [9] [10] [11] [12] [13] [14]

Italy

[15]

Indonesia Brazil and Paraguay India India

[16] [17] [18] [19] [20] [21] [22] [21]

D. 2009: Brazil and Paraguay Blackout [18] [19]

Fig. 1: Sequence of Events Prior to Blackout (Northeast Blackout, 2003).

C. 2003: Italian Blackout [15] Italy faced a nationwide power failure on September 28, 2003 affecting nearly 60 million people. A major share of electricity was imported in Italy from its neighboring countries viz. Switzerland, Austria, Slovenia, France and Italy. The series of events leading to blackout started with the tripping of two heavily loaded transmission lines near the Italy-Switzerland border. High current flow through the line caused the conductors to heat up and sag, thereby decreasing the distance between line conductors and trees resulting in a flashover. The Italian electrical system started to loss synchronism. Consequently, the voltage started to decrease resulting in additional loss of transmission lines due to operation of distance relays. Hereafter, Italy lost transmission links from rest of the neighboring countries resulting in loss of 6400 MW of power. Thereby, the frequency of the system declined and once it reached below 47.5 Hz, the generators tripped due to under frequency protection scheme.

The blackout in Brazil and Paraguay occurred on 10th November 2009 affecting nearly 70 million people. Heavy rains and strong winds caused the malfunctioning of an insulator. It led to tripping of a 765 kV transmission line due to phase to ground fault. Subsequently within milliseconds of the initial trip, two more 765 kV transmission lines tripped. The transmission lines were connected to Itaipu dam, which is world’s largest hydroelectric dam by energy generation [23]. Hereafter, wide area protection scheme (WAPS) came into effect resulting in automatic shut down of five generators of Itaipu dam. Finally, the affected area broke into islands and collapsed due to generation-load imbalance and power swing. It resulted in partial blackout in Brazil with loss of 28.8 GW load and complete blackout in Paraguay with loss of 980 MW load.

III. INDIAN POWER SYSTEMS AND BLACKOUT E. Overview of Indian Power System Indian power system is divided into five Regional Grids namely Northern (NR), Eastern (ER), Northeastern (NER), Western (WR) and Southern (SR) Grid with their regional load dispatch centers (RLDC) at New Delhi, Kolkata, Shillong, Mumbai and Bangalore respectively. The role of RLDC is to manage, operate and monitor the power systems within their regions and to check for contingencies that could affect the reliability of the system. State Load Dispatch Centers (SLDC) are set up in each state that monitor and manage power within their areas and coordinate with RLDC. National load dispatch center (NLDC) supervises and coordinates with RLDC. NR, ER, WR and NER grids are synchronously connected and operate as NEW grid. The southern grid is asynchronously connected to NEW grid via High Voltage Direct Current (HVDC) link. Table II shows the generation capacity and interconnection of various regional grids as on 30th April 2013[24]. Power Grid

Power Blackouts: Causes and Preventive Measures in Context to Indian Blackouts  5

Corporation of India Limited (PGCIL) looks after transmission of electricity throughout the country [25] [26]. TABLE 2: GENERATION CAPACITY AND INTERCONNECTION OF VARIOUS REGIONAL GRIDS TABLE STYLES Regional Capacity (MW) Grid NR Thermal 37207.75 Nuclear 1620.00 Hydro 15467.75 Other 5589.25 Total 59884.75

Connecting Grids Connected with WR and ER grid by AC lines

WR

Connected with NR and ER grid by AC lines and SR by HVDC lines

NER

ER

SR

States and Union Territories Chandigarh, Delhi, Haryana, Himachal Pradesh, Jammu and Kashmir, Punjab, Rajasthan, Uttar Pradesh, Uttarakhand Thermal 57992.80 Chhattisgarh, Nuclear 1840.00 Gujarat, Madhya Hydro 7447.50 Pradesh, Other 8986.93 Maharashtra, Dadra and Nagar Haveli, Total 76267.23 Daman and Diu, Goa Thermal 1390.24 Arunachal Pradesh, Nagaland, Assam, Nuclear 0.00 Hydro 1242.00 Meghalaya, Manipur, Mizoram, Other 252.68 Total 2884.92 Tripura Thermal 23935.08 Bihar, Jharkhand, Odisha, West Nuclear 0.00 Hydro 4113.12 Bengal, Sikkim Other 454.91 Total 28503.11 Thermal Nuclear Hydro Other Total

31084.60 1320.00 11353.03 12251.85 56009.48

Andhra Pradesh, Karnataka, Kerala, Tamil Nadu, Puducherry

Connected with ER grid by AC lines

Connected with NR, NER and WR grid by AC lines and SR grid by HVDC lines Connected with WR and ER grid by HVDC lines

Government and private owned stations generate electricity, which is then transmitted to the Grid. PGCIL is the regulatory body that schedules interchange of power through grid between different states. Any under/over drawal of power is termed as unscheduled interchange (UI), which is feasible as long as the system frequency lies within the precise limits specified by the Indian Electricity Grid Code [27]. Finally, power distribution companies distribute electricity to the consumers. Fig. 2 shows the power distribution system adopted in India.

monsoon resulted in low hydroelectric supply reducing the power generation. Thus, northern states were excessively drawing power from the grid by utilizing UI. NR grid was importing net 5686 MW of power from WR and ER grid as shown in Fig.3. Many interconnecting power transmission lines between WR and NR grid were not available due to planned outage. Some transmission lines were automatically disconnected due to high voltage [21].Furthermore, one of the two circuits of 400kV BinaGwalior-Agra transmission line was closed for up gradation. It was one of the most important transmission links between WR and the NR grid. Therefore, the power transfer between two grids was taking place in a depleted transmission network. Few hours prior to the grid disturbance, some transmission lines near the WR-NR interface got tripped. Consequently, the load on Bina-Gwalior-Agra line started to build up. NDLC, WRLDC and NRLDC noticed it and started making efforts to reduce network congestion. The NRLDC intimated SLDCs of many states about the high loading of Bina-Gwalior-Agra line and non-availability of its second circuit. It requested SLDCs to reduce power drawal within scheduled limits, but SLDCs paid no heed to it. Finally, Bina-Gwalior-Agra line tripped due to load encroachment. Consequently, distance relays sensed overload and neighboring transmission lines also got tripped. Hence, the direct link between NR and WR grid was lost.

Fig. 2. Power generation and distribution system in India.

F. Reasons Behind the Blackout In July 2012, two consecutive blackouts took place in India. First power outage was due to failure of the Northern regional grid on 30th July. The disturbance started at 02:33 am Indian standard time (IST) and within a matter of seconds the whole grid collapsed. Nearly 300 million people were affected [20]. Second power outage was due to failure of three regional electricity grids on 31st July. This was the worst blackout ever happened till date in the history which, affected nearly 620 million people [22]. The power demand was increased in northern India due to the hot summer season. Moreover, the delay in

Fig. 3: Power Flow Between Different Regional Grids 33 Minutes Prior to


The power from WR to NR grid was then indirectly routed via ER grid (WR-ER-NR), which caused large angular deviations between NR and rest of the NEW grid. Consequently, it gave rise to power swings and this led to cascade tripping of transmission lines. Hereafter, the NR grid got separated from the ER grid. The black line in Fig. 4 shows the axis of separation of NR grid from its interconnecting grids. After separation from rest of the regional grids, the NR region lost import of about 4367 MW [21] of power that led to decline in system frequency. However, to maintain the frequency within precise limits, the NR grid would have shed consumer load via automatic under frequency relays. But due to malfunctioning of these relays, insufficient relief was observed. Hereafter, the system frequency continued to fall and once it reached below 47.5 Hz [21], the generating stations started to trip because of under frequency protection scheme. Ultimately the whole northern grid collapsed resulting in a blackout. The flow chart in Fig. 5 shows factors that led to the 30th July 2012blackout. The second blackout occurred on 31st July 2012 at 13:00 IST. The collapse started in a similar fashion with the tripping of Bina-Gwalior-Agra line. Further, the transmission lines tripped near the WR-NR and WR-ES interface due to load encroachment/power swing conditions. Consequently, WR grid got separated from rest of the NEW grid. Furthermore, the frequency in rest of the NEW grid declined due to loss of import of power from WR grid. Once the frequency fell below 47.5 Hz, the generating stations started to trip due to under frequency protection resulting in a catastrophic blackout.

1) Load encroachment If reactive power support is not adequate under heavily loaded conditions, the load voltage decreases and current increases. Therefore, the load impedance (Z) can fall to such a level that, it lies within the relay operating range. This encroachment of load into the zone 3 characteristic causes malfunction of the distance relay. It results in undesired tripping of transmission lines. The initial transmission lines tripping during the grid disturbance was due to load encroachment, which resulted in separation of NR and WR grid on 30th July 2012.

Fig. 4: Transmission Links Between Various Regional Grids. [21]

G. Technical Analysis of Blackouts in India There are many reasons that can cause grid disturbances, load encroachment, power swing and under frequency are few major contributors to this effect. However, under frequency based load shedding and rate of change of frequency (df/dt) based load shedding can help in saving the system during disturbances. The important factors that are responsible for system performance during disturbance are shown in Fig. 6. The major factors, which were responsible for blackout in India, are given below: 

Cascade tripping of transmission lines due to operation of distance relays.



The phenomenon ‘Load encroachment’ and ‘power swing’ were responsible for unwanted operation of distance relays.



Insufficient frequency based load shedding.



Generator tripping due to under frequency.

The following sub sections discuss the factors, which are used to analyze the system performance during disturbances. These are:

Fig. 5: Sequence of Events that Led to Blackout

Fig. 6: Factors Responsible for System Performance during Disturbances

Power Blackouts: Causes and Preventive Measures in Context to Indian Blackouts  7

I.

2) Power swing In power systems the generators run in synchronism with each other. In case of small disturbances, the system tends to stabilize itself with the help of restorative torques. In case of large disturbance, restorative torques may be ineffective and the angular separation (δ) between generators in parallel increases. The impedance of a line is a function of phase angle separation (δ)[28]. The disturbances have oscillatory response. The oscillations are known as power swings. They can cause the load impedance to lie within the relay operating range resulting in malfunctioning of distance relays. During the disturbance on 30th July 2012, the frequency of NR region declined. It resulted in angular separation between NR and WR region as shown in Fig. 7. This caused severe power swings, which triggered the undesired tripping of transmission lines.

Some common factors and their preventive measures are shown in Table III, which are involved in blackouts. The Indian blackout showed loopholes in the distribution sector. The preventive measures to overcome such loopholes are described below: 1.

Scheduled maintenance to rectify malfunctioning of equipments.

2.

Restructuring of power boards should be done strictly without any political interference.

3.

Advanced monitoring devices like Phasor Measurement Unit (PMU) will help the system operator to detect disturbances and then restore the system.

4.

Application of Superconducting Magnetic Energy Storage (SMES) units at interfaces between the grids can help is storing power for a small time, enabling control systems to catch up with the speed of propagating power overload and isolate the point having a load higher than critical load. This concept was used in northern Wisconsin, a U.S. state, where SMES were used on transmission lines, which lead to grid stability.

5.

System operators should undergo regular trainings for better operation and control of the grid.

6.

To make system more reliable, the transmission sector should be opened for private players.

7.

Using advance methods to control the undesired operation of distance relays during load encroachment and power swing conditions [30] [31].

8.

Generators must be made to run on free governance mode for automatic frequency control.

9.

Extensive studies should be done for implementing islanding scheme. Islanding of critical sectors such as Indian Railways and Metro can reduce the burden of blackouts.

3) Frequency based load shedding Due to overloaded conditions, system frequency drops. If there is inadequate generation, load shedding (cutting electricity to consumers temporarily) is done to bring the frequency back within the safe limits. Frequency based load shedding is of two types a.

Under frequency load shedding.

b.

Rate of change of frequency (df/dt) load shedding. th

During grid disturbance on 30 July, the NR region lost import of 4367 MW of power after disconnecting from rest of regional grids. The system frequency began to decline. The NR grid can shed 4000 MW of load via under frequency based load shedding and 6000 MW of load via df/dt load shedding [21]. But insufficient load shedding was observed on that day. The frequency-based relays were malfunctioned.

4) Under frequency Generators are the most expensive unit in a power system. So their manufacturers give enough protection to them. The generators are not allowed to operate below 47.5 Hz. If the system frequency goes down, the generators get automatically shut down to avoid disturbances. According to the Indian Electricity Grid Code, the system frequency should be maintained between 49.5 to 50.2 Hz [29]. Before the blackout, the system was maintaining frequency well within the limits as shown in Fig. 8. But, due to the cascade tripping of transmission lines, the system frequency declined sharply and went below 47.5 Hz within few seconds of the initiation of the disturbance. The generators started to trip and the whole system crashed.

FACTORS RESPONSIBLE FOR BLACKOUTS AND PREVENTIVE MEASURES

Fig. 7: Frequency Profile and Angular Separation between Kanpur (NR) and Jabalpur (WR) on 30th July 2012.([21])


be installed at more locations for better protection and control [32].

Fig. 8: Frequency Profile on 30th July 2012. ([21]) TABLE 3: CAUSES BEHIND BLACKOUTS AND THEIR REMEDIES Factors Leading to a Blackout Preventive Measures Scheduled maintenance to rectify Initiation of Disturbance malfunctioning of equipments It can start because of line tripping, equipment malfunction, Monitoring vegetation to reduce the false operation of relays, human possibility of a flashover between error, short circuit, natural line conductors and trees calamity etc. Advanced monitoring devices like Phasor Measurement Unit (PMU)will help the system operator to detect disturbances and then restore the system Advanced methods such as Cascade Of events Differential-like ImpedanceA chain reaction of tripping of Algorithm (DIA) can prevent transmission lines due to voltage distance relay malfunction due to instability, power swings, load load encroachment [30] encroachment etc. Synchronized Sampling based Fault Location (SSFL)algorithm can prevent distance relay malfunction during power swings [31] Phasor Measurement Units (PMU)can help in better protection and control of power systems [32]

Formation of Uncontrollable Islands

Flexible Alternating Current Transmission Systems (FACTS) devices will control voltage instability [33] [34] Better implementation of islanding schemes

Formation of Islands is due to cascade tripping of transmission lines

1.

2.

The generation capacity of renewable energy resources should be increased, which can reduce the peak load demand and power imbalances. The conventional grid should be converted into a Smart Grid whose salient features are: 

Implementing SCADA for better monitoring and control of electrical systems [35].



Advanced monitoring systems such as Phasor Measurement Units (PMU) and Wide Area Measurement System (WAMS) should



Installation of Flexible Alternating Current Transmission Systems (FACTS) devices to increase controllability and optimize the utilization of the existing power system capacities. [33] [34]



Smart Meters should replace conventional meters.



Integration of renewable energy sources to grid.

IV. DISCUSSION Undoubtedly, blackouts bring lot of difficulties and inconvenience. But at the same time, they provide an opportunity to look for innovative ideas that will lead to technological advancements, which will make the system more immune to blackouts. There can be many reasons, technical and natural calamities, which can lead to blackout. Keeping aside the blackouts due to natural calamities, efforts have to be made to avoid such blackout incidents. The grid indiscipline and load variations have posed major challenges to the secure operation of the system. Strict action should be taken against the utilities, which violates the grid code. In a power deficit country like India, the introduction of smart grid technology can play a vital role to avoid such power blackouts in future. The solution lies in moving towards effective control and protection by implementing SCADA.

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Fairley, P. (2004). The unruly power grid, IEEE Spectrum, 41 (8), 16-21. Talukdar, S.; Apt J.; Ilic M.; Lave L; and Morgan, M. (2003). Cascading failures: survival versus prevention,The Electricity Journal, 16 (9), 25-31. Buldyrev, S.V.; Parshani, R.; Paul, G.; Stanley, H.E.; and Havlin, S. (2010). Catastrophiccascadeof failures in interdependent networks. Nature, 464 (7291), 1025-1028. Parshani, R.; Buldyrev, S.V.; and Havlin, S. (2010). Interdependent networks: reducing thecoupling strength leads to a change from a first to second order percolation transition.Phys. Rev. Lett., 105:048701. The Great Northeast Blackout of 1965. [Online], Available: http://www.rense.com. Report on the power failure in the northeastern United States and the province of Ontario on November 9-10, 1965. [Online], Available: http://blackout.gmu.edu. In March 1989, Quebec experienced a blackout caused by a solar storm. Hydro Quebec. [Online], Available: http://www.hydroquebec.com. The HydroQuebec Blackout of March 1989. Windows to the Universe.[Online], Available:http://www.windows2universe.org. Neves, F.; The Darkest Night. [Online], Available: http://www.brazzil.com

Power Blackouts: Causes and Preventive Measures in Context to Indian Blackouts  9 [10] World: Americas Lightning knocked out Brazil power. BBC news. [Online], Available: http://www.bbc.co.uk/news. [11] India's entire northern electricity grid collapses for 12 hours. World Socialist Web Site.[Online], Available: http://www.wsws.org. [12] Collapse of the Northern Regional Grid of India. The Energy and Resource Institute. [Online], Available: http://www.teriin.org. [13] Andersson, G.; Donalek, P.; Farmer, R.; Hatziargyriou, N.; Kamwa, I.; Kundur, P.; Martins, N.; Paserba, J.; Pourbeik, P.; Sanchez-Gasca, J.; Schulz, R.; Stankovic, A.;Taylor, C.; and Vittal, V. (2005). Causes of the 2003 major grid blackouts in North America and Europe, and recommended means to improve system dynamic performance, IEEE Transactions on Power Systems, 20 (4), 1922–1928. [14] U.S.-Canada Power System Outage Task Force (2004) Final Report on the August 14, 2003 Blackout in the United States and Canada: Causes and Recommendations. [Online], Available: http://www.nerc.com. [15] Corsi, S.; and Sabelli, C. (2004). General blackout in Italy Sunday September 28th, 2003, h 03:28:00.inProc. IEEE PES General Meeting, Denver, CO, 1691- 1702. [16] Indonesian outage leaves 100m without electricity. Financial times. [Online], Available: http://www.ft.com [17] Massive blackout hits Java, Bali. The Jakarta Post, 19 August 2005. [Online], Available: http://www.thejakartapost.com [18] Conti, J.P. (2010). The day the samba stopped. Engineering and Technology, 5 (4), 46– 47. [19] Filho, J.M.O. (2010). Brazilian Blackout 2009 Blackout watch.PAC World. [20] India blackout leaves 300 million without power. Reuters. [Online], Available: http://in.reuters.com. [21] Report on the grid disturbance on 30th July 2012 and 31st July 2012, Submitted on 8th August to Central Electricity Regulatory Commission (CERC). [Online], Available: http://www.cerind.gov.in

[22] Second day of India’s electricity outage hits 620 million. USA today. [Online], Available: http://www.usatoday.com. [23] http://www.itaipu.gov.br [24] http://www.cea.nic.in. [25] http://www.powergridindia.com. [26] http://www.pocoso.in. [27] http://www.cercind.gov.in. [28] Power Swing and Out-of-Step Considerations on Transmission Lines. (2005).IEEE PSRC WG D6. Final draft. [29] Clause 5.2(m) of the CERC (Indian Electricity Grid Code) Regulations, 2010. [Online], Available: http://www.cerind.gov.in [30] El-Hadidy, A.; and Rehtanz, C. (2010). Blocking of Distance Relays Zone3 under Load Encroachment Conditions- A New Approach Using Phasor Measurements Technique. Proceedings of the 14th International Middle East Power Systems Conference(MEPCON’10), Cairo University, Egypt, Paper ID 200. [31] Zhang, N.; and Kezunovic, M.(2005). A study of synchronized sampling based fault location algorithm performance under power swing and out-of-step conditions.Power Tech, IEEE Russia, 1-7. [32] Ree, J.D.L; Centeno, V.; Thorp, J.S.;and Phadke, A.G. (2010).Synchronized phasor measurement applications in power systems, IEEE transactions on smart grid, 1 (1). 20-27. [33] Zhang, X.P.; Rehtanz, C.; and Pal, B. (2006).Flexible AC Transmission Systems: Modelling and Control, Springer. [34] Acharya, N.; Sody-Yome, A.; and Mithulananthan, N. (2005). Facts about flexible ac Transmission systems (FACTS) controllers: Practical installations and benefits. Australasian Universities Power Engineering Conference (AUPEC), Australia, 533-538. [35] Boyer, S. (2009). SCADA: Supervisory Control and Data Acquisition, International Society of Automation.

Design and Implementation of UPQC Model to Solve Power Quality Problems Amandeep Kaur

Lini Mathew

M.E. (I & C) Student, Electrical Engineering Deptt., NITTTR, Chandigarh, India e-mail: [email protected]

Associate Professor, Electrical Engineering Deptt. NITTTR, Chandigarh, India e-mail: [email protected]

Abstract—Power quality has become an important factor in power systems, for household appliances with production of various electric and electronic equipment and computer systems. The main reasons of poor power quality are harmonic currents, reduced power factor, supply voltage variations etc. The Unified Power Quality Conditioner (UPQC) is a custom power device, which diminishes voltage and current related power quality issues. It also prevents load current harmonics from entering the utility and corrects the input power factor of the load. This paper deals with conceptual study of Unified Power Quality Conditioner (UPQC) during voltage sag and swell on the power network. The system performance for current, voltage harmonics, voltage sag and voltage swell have been evaluated. The results obtained by means of the MATLAB/ SIMULINK based simulations support the functionality of the UPQC. Keywords: UPQC, Voltage Sag, Voltage Swell, UPQC Topologies etc

I.

INTRODUCTION

In today's complex electronics environment, many problems can occur because of poor quality of power. Therefore, it has become necessary to provide a dynamic solution with greater degree of accuracy as well as with fast speed of response. With great advancement in all areas of engineering, mainly, digital processing, control systems, and power electronics, the load characteristics have changed totally. In addition to this, loads are becoming very sensitive to voltage supplied to them. The power electronics based devices have been used to overcome the major power quality problems [1]. There are sets of conventional solutions to the power quality problems, which have existed for a long time. However these predictable solutions use passive elements and do not always respond correctly as the nature of the power system conditions change. The power electronic based power conditioning devices can be effectively utilized to improve the quality of power supplied to customers. One modern solution that deals with both load current and supply voltage imperfections is the Unified Power Quality Conditioner (UPQC) [2], which was first presented in 1995 by Hirofumi Akagi.

UPQC is a combination of series and shunt active filters connected in cascade via a common dc link capacitor. The series active filter introduces a voltage, which is added at the Point of Common Coupling (PCC) such that the load-end voltage remains unaffected by any voltage disturbance. The main objectives of shunt active filter are: to compensate the load reactive power demand and unbalance, to eliminate harmonics from the supply current, and to control the common dc link voltage. It uses a pair of three-phase controllable bridges to produce current that is injected into a transmission line using a series transformer. The controller bridge can control active and reactive power flows in a transmission line [3]. In case of UPQC, the DC link voltage requirement for the shunt and series active filters is not the same; the shunt active filter requires higher DC link voltage when compared to the series active filter for proper compensation. The shunt active filter provides a path for real power flow to aid the operation of the series compensator and to maintain constant average voltage across the DC storage capacitor. With the high value of DC link capacitor, the Voltage Source Inverters (VSI) becomes bulky and the switches used in the VSI also need to be rated for higher value of voltage and current [4]. This increases the entire cost and size of the VSI. In literature, a hybrid filter has been discussed for motor drive applications. This filter is connected in parallel with diode rectifier and tuned at 5thharmonic frequency. In simpler words, Power quality is a set of electrical boundaries that allow a piece of equipment to function in its intended manner without significant loss of performance. Although asophisticated work, the design is specific to the motor drive application and the reactive power compensation is not considered, which is an important aspect in shunt active filter applications[5]. The paper is organized as follows. The structure of the UPQC is presented in Section II. In Section III, the configuration of UPQC is described in detail. The simulation results are presented in Section IV. Simulation results in this section demonstrate the efficacy and versatility of proposed design technique. Finally, Section V gives the conclusion.

Design and Implementation of UPQC Model to Solve Power Quality Problems  11

II.

STRUCTURE OF UPQC

A. Need of UPQC The increased use of automatic equipment, like adjustable speed drives, programmable logic controllers, switching power supplies etc. are far more vulnerable to disturbances than were the previous generation equipment and less automated production and information systems. Even still the power generation in most advanced country is properlyreliable, the distribution is not always so [6]. It is though not only reliability that the consumers want these days, superiority too is very important for them. With deregulation of the electric power energy marketplace, the awareness regarding the quality of power is increasing day by day among customers. Power quality is aproblem that is becoming increasingly important to electricity consumers at all levels of usage. New generation loads that use microprocessor and microcontroller based controls and power electronic devices, are more sensitive to power quality deviations than that equipment used in the past [7]. The main power quality problems are voltage sag, voltage swell, interruption and harmonic distortion. Voltage sag is a brief decrease of 10 to 90 per cent in the rms value of the nominal line-voltage. The duration of sag is 0.5 to 1 minute. Common sources that contribute to voltage sags are the starting of large induction motors and utility faults. A swell is a brief increase in the rms line-voltage of 10 to 80 per cent of the nominal linevoltage for duration of 0.5 to 1 minute. The main sources of voltage swells are line faults and incorrect tap settings in tap changers in substations. An interruption is defined as a reduction in line-voltage or current to less than 10 per cent of the nominal. Interruptions can occur due to power system faults, apparatus failures and control malfunctions [8]. When the supply voltage has been zero for a period of time in excess of 1 minute, the long-duration voltage variation is considered a sustained interruption. Voltage fluctuations are relatively small (less than 5 per cent) variations in the rms line voltage. Harmonics are sinusoidal voltages or currents having frequencies that are integer multiples of the frequency at which the supply system is designed to operate, which is known as fundamental frequency (usually 50 Hz). The harmonic distortion originates in the nonlinear characteristics of devices and also on loads connected to the power system. Thus in this scenario in which customers increasingly demand power quality, term power quality attains increased significance [9].

B. Basic Structure of UPQC The best protection for sensitive loads from sources with inadequate quality is shunt-series connection i.e. Unified Power Quality Conditioner (UPQC). Unified

power quality conditioners are viable compensation devices that are used to ensure that delivered power meets all required standards and specifications at the point of installation. The UPQC is a custom power device that joins the series and shunt active filters, connected back-toback on dc side and sharing a common DC capacitor, as shown in Fig. 1.This dual functionality makes the UPQC as one of the most suitable devices that could solve the problems of both consumers as well as of utility. UPQC, thus can help to increase voltage profile and hence the overall health of power distribution system. UPQC consists of two IGBT based Voltage Source Converters (VSC) that are connected to a common DC energy storage capacitor and an inductor and also consists of two filter banks. One of these two VSCs is connected in series with the feeder and the other is connected in parallel to the same feeder [10].The series compensator is operated in PWM voltage controlled mode. Whenever the supply voltage undergoes sag then series converter injects suitable voltage with supply. The series filter suppresses and isolates voltage based distortions, while the shunt filter cancels current-based distortions [11].

Fig. 1: General Structure of UPQC

The main purpose of a UPQC is to compensate for supply voltage flicker/ imbalance etc. The UPQC, therefore, is expected as one of the most powerful solutions to large capacity sensitive loads to voltage flicker/imbalance. UPQC maintains load end voltage at the rated value even in the presence of supply voltage sag. The voltage injected by UPQC to preserve the load end voltage at the desired value is taken from the same dc link, thus no additional link voltage support is required for the series compensator [12].

C. Facilities Provided by UPQC 

It eliminates the harmonics in the supply current, therefore improves utility current quality for nonlinear loads.



UPQC provides the VAR requirement of load, so that the supply voltage and current are constantly in phase, therefore, no additional power factor correction equipment is necessary.




UPQC maintains load end voltage at the rated value even in the presence of supply voltage sag/ swell.

The voltage inserted by UPQC to maintain the load end voltage at the desired value is taken from the dc link, thus no additional dc link voltage support is required for the series compensator [13].

III. CONFIGURATION OF UPQC The Unified Power Quality Conditioner (UPQC) is a device that is employed in the distribution system to mitigate the disturbances that affect the performance of sensitive and/ or critical load. It is the only versatile device which can mitigate several power quality problems related with voltage and current simultaneously. It is multi functioning device that compensate various voltage disturbances of the power supply, to accurate voltage fluctuations and to prevent harmonic load current from entering the power system [14]. UPQC consists of two IGBT based Voltage Source Converters (VSC), one in shunt and one in series. The shunt converter is connected in parallel to the load. Whenever the supply voltage undergoes sag then series converter injects suitable voltage with supply. Thus UPQC improves the power quality by preventing load current harmonics and by correcting the input power factor.It consists of a series voltage-source converter connected in series with the AC line and acts as a voltage source to diminish voltage distortions. It is used to remove supply voltage flickers or imbalance from the load terminal voltage and forces the shunt branch to absorb current harmonics generated by the nonlinear load. Control of series converter output voltage is usually performed by pulse-width modulation (PWM). The gate pulses required for converter are generated by fundamental input voltage reference signal [15]. It consists of a voltage-source converter connected in shunt with the same AC line and acts as a current source to cancel current distortions, compensate reactive current of load, and improve the power factor. The gate pulses required for converter are generated by fundamental input current reference signal. It also consists of two transformers. These are implemented to insert the compensation voltages and currents, and for purpose of electrical isolation of UPQC bridge converters. The UPQC is capable of steady-state and dynamic series and/or shunt active and reactive power compensations at fundamental and harmonic frequencies [16].

The shunt active filter is responsible for power factor correction and compensation of load current harmonics and unbalances. Also, it maintains constant average voltage across the DC storage capacitor. The series active filter compensation goals are achieved by injecting voltages in series with the supply voltages such that the load voltages are balanced and undistorted, and their magnitudes are maintained at the desired level. This voltage injection is provided by dc storage capacitor and the series VSI. The control scheme of the shunt active power filter must calculate the current reference waveform for each phase of the inverter, maintain dc voltage constant, and generate inverter gating signals [17].

A. System Parameters The parameters of the VSI need to be designed carefully for better tracking performance. The important parameters that need to be taken into consideration while designing conventional VSI are V, Csh, Lsh, Lse, Cse and frequency (f) and are listed in Table 1. TABLE 1: SYSTEM PARAMETERS System Quantities Source Inverter Parameters Input RC Load Output RL Load Power Factor Transformer 1 Transformer 2 Shunt VSI Parameters Series VSI Parameters

Values 3-Phase,25kV, 50Hz IGBT based, 3-arm, 6-Pulse Active Power=5MW Capacitive Power=2MW Active Power=3GW Inductive Power=1kW 0.9 Y /25kV/600V / Y 600/600V Voltage=600V, Lsh=1mH Csh=1mF Voltage=600V, Lse=1mH Cse=1mF

IV. SIMULATION RESULTS In order to verify the effectiveness of control system with realistic parameters, a MATLAB/ SIMULINK based digital simulation of a system has been carried out as shown in Fig. 5. The performance of UPQC has been analyzed under different conditions such as voltage sag and swell.

A. Proposed Simulation Model of UPQC The SIMULINK model of test system is shown in Fig 5. The system contains two controllers, one is connected in series and other is connected in parallel. It also contains transformers and filter banks for desirable output. The system is tested under different load conditions. A variable load is used to provide constant current output.


Fig. 7: Shunt Controller Fig. 5: Proposed Simulation Model of UPQC

The series controller shown in Fig. 6 is designed to inject a dynamically controlled voltage in magnitude and phase into the distribution line via a coupling transformer to correct load voltage. This is known as Dynamic Voltage Regulator (DVR) which is popularly used as a series connected custom power device [18].

B. Simulation Output of UPQC In order to show the impact of sag and swell variation, a MATLAB/ SIMULINK based simulation is carried out.

Fig. 8: Reference Voltage and Current

Figure 8 shows the three phase reference voltage and current waveforms when UPQC is not connected in system. These are constant in phase as well as in amplitude. Fig 9 shows the control firing pulses for bridge converters. Each bridge contains six IGBTs and each IGBT requires a firing pulse at its gate terminal. These input pulses are required to ON the bridges.

Fig. 6: Series Controller

The purpose of the Shunt Controller is to compensate current unbalance, current harmonics and load reactive power demand fed to the supply [19]. The coupling of shunt controller is three phase, in parallel to network and load as shown in Fig. 7. It works as current sources, connected in parallel with the nonlinear load, generating harmonic currents the load requires. This is same as the popularly known shunt connected custom power device, D-STATCOM [20]. UPQC is a combination of DVR and D-STATCOM.

Fig. 9: Control Firing Pulses for UPQC Bridges

C. Effect of Voltage Swell A voltage swell of 50 % is now introduced in the system for atime span ranging from t = 0.2 sec to t = 0.4 sec,


as shown in the Fig. 10. Under this condition the series controller injects an out of phase compensating voltage in the line through series transformers. The currents are unbalanced and distorted; the terminal voltages are also unbalanced and distorted.

sec to t = 0.4 sec as shown in Fig. 12. During this voltage sag condition, the series controller is providing required voltage by injecting in phase compensating voltage (50 %). The load output waveforms shown in Fig. 13 shows that UPQC is maintaining it at desired constant voltage level at load even during the sag on the system such that the loads cannot see any voltage variation.

Fig. 10: Input Voltage and Current at Swell of 50 %

Fig. 12: Input Voltage and Current at Sag of 50 %

Fig. 11: Constant Output Voltage and Current with UPQC when Voltage Swell of 50 % has Occurred

The load output profile in Fig. 11 shows the UPQC is effectively maintaining the load bus voltage at desired constant level even during the swell on the system such that the loads are not affected by any voltage variation. In other words, the extra power due to the voltage swell condition is fed back to the source by taking reduced fundamental source current. The proposed UPQC maintained the load voltage free from swelling and at the desired level. The above system model has been analyzed by varying the voltage swell from 10 % to 80 % for a time span of 0.2 seconds ranging from t = 0.2 sec to t = 0.4 sec. The input waveforms are highly unbalanced. The load output voltage and current shows that the UPQC effectively maintains the load bus output at desired constant level. It is seen that that voltage and current levels are maintained at desirable levels and the distortion is considerably reduced below 2 %.

D. Effect of Voltage Sag A voltage sag of 50 % is now introduced on the same model of the system for a time span ranging from t = 0.2

Fig. 13: Constant Output Voltage and Current with UPQC when VoltageSag of 50 % Occurred

This system is again analyzed by varying the voltage sag from 10 % to 80 % for a time span of 0.2 sec ranging from t = 0.2 sec to t = 0.4 sec. Before and after this time, the system is again at normal working condition. The load output profile in all these conditions show that it produces a constant output voltage and current when UPQC is connected to a system. This system is again analyzed by varying the voltage sag from 10 % to 80 % for a time span of 0.2 sec ranging from t = 0.2 sec to t = 0.4 sec. Before and after this time, the system is again at normal working condition. The load output profile in all these conditions show that it produces a constant output voltage and current when UPQC is connected to a system.


E. Effect of Voltage Sag and Swell on Voltage and Current with Increased Duration A voltage swell and sag of 50 % is now introduced in the system for a time span ranging from t = 0.5 sec to t = 2 sec, as shown in the Fig. 14 and Fig. 15 respectively. Under this condition, the currents are unbalanced and distorted; the terminal voltages are also unbalanced and distorted. The load output waveforms shown in Fig. 16 shows that UPQC is maintaining it at desired constant voltage level at load even during the sag or swell for longer duration on the system.

F. Effect of Harmonics The harmonics have the property that they are all periodic at the fundamental frequency; therefore the sum of harmonics is also periodic at that frequency. Harmonic frequencies are correspondingly spaced by the width of the fundamental frequency and can be found by repeatedly adding that frequency. Harmonics are the multiple of the fundamental frequency. They occur frequently when there are large numbers of personal computers (single phase loads), Uninterruptible Power Supplies (UPS), variable frequency drives (AC and DC) or any electronic device using solid state power switching supplies to convert incoming AC to DC. Non-linear loads generate harmonics by drawing current in abrupt short pulses as shown in Fig. 17 and its output is shown in Fig. 18.

Fig. 14: Input Voltage and Current at Swell of 50 % with Increased Duration Fig. 17: Input Voltage and Current having 5th Order Harmonics

Fig. 15: Input Voltage and Current at Sag of 50 % with Increased Duration

Fig. 18: Output Voltage and Current with UPQC having No 5th Order Harmonics

G. Effect of Interruption

Fig. 16: Constant Output Voltage and Current with UPQC when Voltage Sag or Swell of 50 % with Increased Duration has Occurred

A voltage interruption is a large decrease in RMS voltage to less than a small per centile of the nominal voltage, or a complete loss of voltage. Voltage disruptions may come from accidents like faults and component malfunctions, or from planned downtime. Short voltage interruptions are typically the result of a malfunction of a switching device or a deliberate or inadvertent operation of a fuse, circuit breaker, or reclose in response to faults and disturbances. Long interruptions are usually resulting of scheduled downtime, where part of electrical power


system is disconnected in order to perform maintenance or repairs. When a three phase fault is introduced in the system having duration 0.16 to 0.84 sec, it generates an interruption in the input signal as shown in Fig. 19. When UPQC is connected within the system, it resolves this power quality problem and provide us constant output signal as shown in Fig. 20. The analysis of input and output signals can be done by FFT Analysis tool provided in Simulink block. The analysis of input waveform having harmonics is given by Fig. 21. The upper part shows the input voltage signal having 5th order harmonics and lower part shows its fundamental frequency components present in the signal and also provides Total Harmonic Distortion (THD). Similarly, Fig. 22 shows the output waveforms of input harmonic signal and their FFT analysis. The THD in Fig. 22 shows that this output signal is distortion free.

Fig. 19: Input Voltage and Current Waveforms having Harmonics and Interruption

Fig. 20: Output Voltage and Current Waveforms with UPQC having No. Harmonics and Interruption

4

2

Selected signal: 50 cycles. FFT window (in red): 2 cycles

x 10

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Fundamental (50Hz) = 1.348e+04 , THD= 16.39%

Mag (% of Fundamental)

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600

Fig. 21: Input THD having Harmonics and Interruption

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Design and Implementation of UPQC Model to Solve Power Quality Problems  17 [6] Selected signal: 50 cycles. FFT window (in red): 2 cycles 500

[7]

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[9]

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Fig. 22: Output THD having No. Harmonics and Interruption

[11]

V. CONCLUSION In this paper, the simulation results shows that UPQC can be employed to reduce the distortion level and highly improve the power quality of the system. Due to its reliability, it was adopted as the optimal solution for the compensation of voltage and current. This paper investigated the application of UPQC for power quality improvement and implementation of a flexible control strategy to enhance the performance of UPQC. In order to protect critical loads from more voltage harmonics, UPQC is suitable and satisfactory. The objectives have been successfully realized through software implementation in MATLAB/ SIMULINK.

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[2]

[3]

[4]

[5]

Nikita Hari, K. Vijayakumar and Subhranshu Sekhar Dash, “A Versatile Control Scheme for UPQC for Power Quality Improvement”, Proceedings of the International Conference on Emerging Trends in Electrical and Computer Technology (ICETECT), pp 453-458, 23-24 March 2011. Srinivas Bhaskar Karanki, Mahesh K. Mishra and B. Kalyan Kumar, “Comparison of Various Voltage Source Inverter based UPQC Topologies”, Proceedings of the International Conference on Power and Energy Systems (ICPS), pp 1-7, December 2011. Vinod Khadkikar, “Enhancing Electric Power Quality Using UPQC: A Comprehensive Overview”, IEEE Transactions on Power Electronics, Vol. 27, No. 5, pp 2284-2297, May 2012. K. Palanisamy, J Sukumar Mishra, I. Jacob Raglend and D.P. Kothari, “Instantaneous Power Theory Based Unified Power Quality Conditioner (UPQC)”, 2010 Joint International Conference on Power Electronics, Drives and Energy Systems (PEDES), pp 1-5, 20-23 December 2010. Malabika Basu, S. P. Das and Gopal K. Dubey, “Performance Study of UPQC-Q for Load Compensation and Voltage Sag Mitigation”, Proceedings of the IEEE 28th Annual Conference of the Industrial Electronics Society (IECON 02), Vol. 1, pp 698-703, November, 2002.

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Salmeron P., Litran S.P., “Improvement of the Electric Power Quality Using Series Active and Shunt Passive Filters”, IEEE Transactions on Power Delivery, Vol. 25, No. 2, pp. 1058-1067, April 2010. V. Khadkikar,A. Chandra, A. O. Barry and T. D. Nguyen, “Application of UPQC to Protect a Sensitive Load on a Polluted Distribution Network”, IEEEPower Engineering Society General Meeting, 2006. Singh B., Al-Haddad K., Chandra A., “A review of active filters for Power Quality Improvement”, IEEE Transaction on Industrial Electronics, Vol. 46, No. 5, pp. 960-971, August 2002. G. Siva Kumar, B. Kalyan Kumar and Mahesh K. Mishra, “Mitigation of Voltage Sags with Phase Jumps by UPQC with PSO-Based ANFIS”, IEEE Transactions on Power Delivery, Vol. 26, No. 4, pp 2761-2773, October 2011. Saleh S.A., Moloney C.R., Rahman M.A., “Implementation of a Dynamic Voltage Restorer System Based on Discrete Wavelet Transforms”, IEEE Transactions on Power Delivery, Vol. 23, No. 4, pp. 2366-2375, October 2008. Subramanian Muthu and Jonathan M. Kim “Steady-State Operating Characteristics of Unified Active Power Filters”, twelfth annual Applied Power Electronics Conference and Exposition (APEC), Vol. 1, pp 199–205, February 1997. Morris Brenna, Roberto Faranda and Enrico Tironi, “A New Proposal for Power Quality and Custom Power Improvement: OPEN UPQC”, IEEE Transactions on Power Delivery, Vol. 24, No. 4, pp 2107-2116, October 2009. Sudeep Kumar R and Ganesan P, “250 kVA Unified Power Quality Controller”, Proceedings of the IEEE Region 10 Conference (TENCON), Hong Kong, pp 1–4,November 2006. V. Khadkikar, A. Chandra, A. 0. Barry and T. D. Nguyen, “Conceptual Study of Unified Power Quality Conditioner (UPQC)”, Proceedings of the IEEE International Symposium on Industrial Electronics 2006, Canada, Vol. 2, pp 1088-1093, July 2006. Vinod Khadkikar and Ambrish Chandra, “A New Control Philosophy for a Unified Power Quality Conditioner (UPQC) to Coordinate Load-Reactive Power Demand Between Shunt and Series Inverters” IEEE Transactions On Power Delivery, Vol. 23, No. 4, October 2008. V. Khadkikar,A. Chandra, A. O. Barry and T. D. Nguyen, “Application of UPQC to Protect a Sensitive Load on a Polluted Distribution Network”, IEEE Power Engineering Society, General Meeting, 2006. B. S. Mohammed, K. S. Rama Rao and P. A. Nallagownden, “Improvement of Power Quality of a Two Feeder System using Unified Power Quality Conditioner”, Proceedings of the National Postgraduate Conference (NPC), pp 1-6, September 2011. Ramachandaramurthy V.K., Arulampalam A., FitzerC., Zhan C., Barnes M., Jenkins N., “Supervisory Control of Dynamic Voltage Restorers”, IEEE Proceedings-Generation, Transmission and Distribution, Vol. 151, No. 4, pp. 509-516, 11 July, 2004. Singh M., Khadkikar V., Chandra A., Varma R.K., 2011. Grid Interconnection of Renewable Energy Sources at the Distribution Level with Power-Quality Improvement Features, IEEE Transactions on Power Delivery, Vol. 26, No. 1, pp. 307-315, January 2011. A.Jeraldine Viji and M.Sudhakaran, “Generalized UPQC system with an improved Control Method under Distorted and Unbalanced Load Conditions”, Proceedings of the International Conference on Computing, Electronics and Electrical Technologies (ICCEET), pp 193-197, 2012.

Virtual Labor L atory for Teests onn Trannsform mer N Neeraj Kumaar Reesearch Schola ar, B.M. Univversity, Rohtakk, Haryana e-mail: [email protected]

Raj ajesh Kumar

Lini Matheew

Department of Electricall Engg., G.P. Nilokheri, N Karnnal e-mail: raj [email protected]

Associate Proffessor, A Departtment of Electr trical Engg., N NITTTR, Chanddigarh

Abstract— —Software bassed Laboratoryy experiments have become curreent day need due to its impact i on fleexible learning of sttudents and better b concepttual understan nding abilities. Virtu ual laboratoriees for online experimentatio e on are a highly signiificant and efffective develop pment in this area. However, Electrical Engineeering experim ments are geneerally difficult to mechanize due to thee risks of high voltages/curreents associated d with them. In n addition diggitally controllable ellectrical machiines are expen nsive and not widely w found in manyy laboratories. In this paperr, development of a virtual laboraatory for differrent experimen nts on transforrmers using Simulin nk, LabVIEW and NIUSB60008 DAQ card d has been presented d. Keywordss: Virtual laborratory, Online experiments, e V Virtual I Instrumentatio on, LabVIEW W, Data acquisition syystem, Simulation Intterface Toolkit (SIT).

I.

INT TRODUCTION N

The trannsformer is a static device that transferrs the electrical eneergy from onne electrical circuit to anoother circuit at sam me frequencyy through magnetic flux. The windings (prrimary and secondary) s of the transfoormer are coupledd magneticaally with each other [11]. Laboratory sessions s playy an importaant role in many m scientific orr technical venture to understand the theoretical concepts. However, H inn many cases, c f to perform expperiments reqquire laboratory facilities large investtments in terms t of innitial cost, and maintenance.. In additioon, electricaal machines are expensive annd sometimes all machinerry required, as a per curriculum, is not available in i conventional laboratories. Virtual labooratories are portable and also o the electtrical students cann perform online tests on machines [1], [3]. In thhis paper noo load test, short circuit test, parallel operations of transformerss are illustrated byy using LabV VIEW, Simullink and SIT.. The efficiency measurement test is also peerformed by using u a hardware kit, k NIUSB60008 DAQ carrd and LabVIIEW. Control pannel of test has been developed d inn the LabVIEW frront panel. Control C panell displays all the observations of the transfo former under test t at any loaad.

II.

DESC CRIPTION OF THE EXPERIIMENT

Various V expeeriments are pperformed to determine thee param meters and effficiency of thee transformer at any load.

A. No N Load Tesst This test is performed p onn low voltage side of thee transsformer to finnd out the ironn losses of thee transformer. Steps to calculate the losses annd various parrameters at noo load are as under [2]: [ Total iron losses = Wo (Reaading of wattm meter) Wo = Vp Io cossɵo where w Vp is thhe no load volltage. Io is the no loaad current. No N load pow wer factor cosɵ ɵo = Wo / Vp Io Equivalentt resistance represennting the core losses Rc= Vp / Io cosɵo. reactance reppresenting thee magnetizingg Magnetizing M curreent Xm = Vp /Io* sinɵo. The equivaleent circuit ddiagram of trransformer iss show wn in Fig. 1.

Fig. 1 Equiivalent Circuit Diiagram of Transfo ormer

B. Short S Circuiit Test This test is performed p onn high voltag ge side of thee transsformer with short s circuitedd secondary winding w to findd out the t variable/ccopper lossess of the transsformer. Thiss test is performed at the raated load cu urrent of thee transsformer [2].

Virttual Laboratory for Tests on Tra ansformer  19 9

Total coppper losses = Wsc (Reading of wattmeter)) Wsc = Vscc Isc cosɵsc where Vsc c voltaage. s is the short circuited Isc is the short s circuitedd current. Short circcuited power factor cosɵsc = Wsc / Vsc* Isc

C. Parallell Operation of o Transform mer Parallel operation o of transformer t iss performed too see the load sharring by two transformers. Transformerrs are connected in parallel p to suppply excess looad.

D. Online Efficiency E off Transformerr This tesst is perform med to deterrmine the online o efficiency off transformerr at any looad. In this test, efficiency iss measured directly byy measuring the parameters of the transforrmer. In this test control panel p t front paneel of LabVIE EW, which display designed in the the efficiencyy directly. Voltage V and current c sensors of required speccifications aree used to sensse the voltagee and current signalls from transfoormer. NIUSB B6008DAQ caard is used to inteerface the hardware h witth the LabV VIEW front panel.

Fig. 2: Simulinnk Model for no L Load Test on Traansformer

III. SOFTWARE SETUP AND INTERFACE N Virtual Laboratory L foor various tessts on transfoormer has been devveloped by ussing NI LabV VIEW, SIMUL LINK and Simulatioon Interface Toolkit T (SIT). LabVIEW wiith its Graphical prrogramming language l is ideal i for creeating flexible, scaalable, and sophisticated s applications and instruments that t meet thee specific neeeds of a reseearch project. SIM MULINK is a powerful graphical toool of MATLAB thhat involves setting up a model of a real situation and performing analysis a and experiments e o the on b a system. model in reaal time beforre actually building LabVIEW communicatees successffully with the w the help of o SIT [7][10]]. SIMULINK with

Fig. 3: Simulink Model for Short Circuit Test on Transformer T

IV. SIMULINK I MODELS O OF EXPERIMENTS X To perfoorm the testt in virtual laboratory off the considered traansformer, onne can use the available macchine blocks of the Power System ms Block set (PSB) of Sim mulink Library Brow wser. Simulinnk Model for no load testt and short circuit test are shoown in the Fig. F 2 and Fig. 3 respectively. Parallel opeeration of thhe transformeer is described as shown s in Fig. 4.

T Fig. 4: Simulink Model for Paralllel Operation of Transformer

20  Internatio onal Conference e on Recent Advvances and Trends in Electrica al Engineering (R RATEE-2014)

V. LabVIIEW PROGR RAM National Instruments (NI) LabVIE EW is one of the best graphical programm ming softwaree of the world. w LabVIEW stands f for Laboratory Virtual Instrumentation (Instruments) Engineerring Workbench. It is system m design softtware and is used to dev velop virtual instrum ments.

A Front Paanel A. Control panel for various v testss which can n be performed on the transfo ormer has beeen developeed in LabVIEW. Front F panel contains vario ous indicatorss and controls used d to portray the various parameters p o the of transformer. Control paanel for no o load testt on transformer is shown in Fig.5. Conttrol panel forr the short circuit test t on the traansformer is illlustrated in Fig.6. F Control paneel for the parallel operatio on of transforrmers test is describ bed in Fig. 7.

Fig. F 7: Control Paanel for Parallel O Operation test on Transformer

Control paneel for determ mining online efficiency off transsformer has beeen developedd as shown in the Fig.8. Thee efficiency of the transformer can be determ mined at anyy load.. The control panel containns the meter indicator i usedd to in ndicate the primary p voltagge V1 of thee transformer, prim mary current I1 of the transsformer, secon ndary voltagee V2 of o the transsformer, secoondary curren nt I2 of thee transsformer, inpuut power annd output power of thee transsformer. Digittal indicators also used to indicate inputt poweer factor, outtput power faactor, input power, p outputt poweer and % efficciency of the ttransformer.

Fig. 5: Control C Panel forr No Load Test onn Transformer

Fig. 8: Conntrol Panel for Online Measuremeent of Efficiency of Trransformer

B. Block B Diagrram

Fig. 6: Coontrol Panel for Short S Circuit Test on Transformer

The block diagram d contaains the grap phical sourcee codee, also known as G code or block diagram m code. Frontt paneel objects appear as terminnals functions on the blockk diagrram. The bloock diagram for online efficiency off transsformer is as shown s in Fig. 9.

Virttual Laboratory for Tests on Tra ansformer  21 1

Fig. 9: 9 Block Diagram m for Online Meassurement of Efficiencyy of Transformer

Fig.11 Block B Diagram G Generated by SIT for Parrallel Operation oof Transformers

VI. SIMULATION N INTERFACE E TOOLKIT

V HARDW VII. WARE KIT

The Sim mulation Interrface Toolkit (SIT) providdes a seamless inteegration betweeen SIMULIN NK and LabV VIEW [10]. The Simulation S Innterface Toollkit automatiically generates LabbVIEW code to interface with w a SIMUL LINK model resultting in a flexible f and easy-to-use user interface. Thee SIMULINK K model must be configuredd first to communiccate with LabVIEW. Then a LabVIEW W host VI can be created c that automaticallyy calls, runs and interacts withh the SIMULINK model. The T integratioon of LabVIEW annd SIMULINK K avail the advvantages of booth. It results in a powerful p engiineering tool using SIMUL LINK and user friiendly Graphhical user innterface (GUII) of LabVIEW. By B integration of both, the user u only inteeracts with the GU UI of LabVIIEW whereass the SIMUL LINK works in the background. b F 10 displayys the componnents Fig. involved in the interacttion betweenn LabVIEW and SIMULINK. Fig. 11 show ws the LabVIE EW block diaagram code automattically generatted by the SIT T after approppriate mapping of the t Simulink signals with the t componennts of the block diaggram.

Researchers R h have developeed a real time online test forr the measurement m of efficiencyy of a transfo ormer. Fig. 122 show ws the hardwaare kit develooped to perforrm the test. Inn this kit, potential transformerss and currentt transformerss are used u as sensors. Current siignal sensed by b the currentt transsformer is connverted into tthe voltage signal by usingg resistances as perr the requirem ment of the NI USB60088 DAQ Q card.

Fig. 12: Hardw ware Kit

VIII.

Fig. 10: 1 Interfacing off SIMULINK andd LabVIEW

REESULT

Observation of online effficiency meassurement andd load sharing in parrallel operatioon of transform mer are shownn in th he Table 1, 2 and 3 (anneexure A). Forr the no load,


short circuit test and parallel operation of the transformers all the parameters are displayed by various indicators of respective control panel shown in Fig. 5, Fig. 6 and Fig. 7. All the parameters measured with the help of sensors and NI USB6008 DAQ card are indicated by the various respective indicators of the front panel. Digital indicators display the input power, input power factor, output power, and power factor and % efficiency of the transformer. Primary and secondary voltage and current are also displayed by the waveform graphs.

Pr. (I1) in Amp

Sec (I2) in Amp

Input power (watt)

OutPut Power (watt)

205

0.67

0.86

188.4

171.6 0.99 0.986 91.07

Output P.F

% Efficiency

Sec (V2) in volt

280

Input P.F

Pr.(V1) In volt

TABLE 1: OBSERVATION TABLE FOR ONLINE EFFICIENCY OF TRANSFORMER

TABLE 2: OBSERVATION TABLE FOR LOAD SHARED BY SINGLE TRANSFORMER Pr. Voltage (Volt) 220

Load Shared by Single Transformer Sec. Voltage Transformation Load Current (Volt) Ratio (Amp) 323.1 0.68 32.33

TABLE 3: OBSERVATION TABLE FOR LOAD SHARED BY TWO TRANSFORMERS

Pr. Voltage (Volt)

Sec. Voltage (Volt)

Transformatio n Ratio

Load Current (Amp)

Pr. Voltage (Volt)

Sec. Voltage (Volt)

Transformatio n Ratio

Load Current (Amp)

Load Shared by Two Transformers Connected in Parallel Parameters of 1st Transformer Parameters of 2nd Transformer

220

379.5 0.579

18.99

220

379.5

0.579

18.99

IX. CONCLUSION A scalable, cost-effective approach to virtual laboratory for tests on transformer has been discussed in detail revealing the hardware, software and interface details of the setup. Using the models Presented in this paper, more electrical experiments can be automated.

REFERENCES [1]

M.P. Kazmierkowski, M. Liserre, "Advances on Remote Laboratories and e-Learning Experiences (Gomes, L. and GarciaZubia, J., Eds.) (Book News)," IEEE Ind. Electron. Maga., vol. 2, no. 2, pp. , June 2008. [2] P. Raghavendra Pradyumna1, Tarun, Surekha Bhanot, “Remote Experimentation of “No-load Tests on a Transformer” in Electrical Engineering”, Proceedings of IEEE International Conference on Innovative Practices and Future Trends (AICERA), Kottayam, Kerala, India, July 2012. [3] Developing Remote Front Panel LabVIEW Applications (Online), 2010. [4] M. Usama Sardar, “Synchronous Generator Simulation Using LabVIEW”, Proceedings of World Academy of Science Engineering and Technology, Academic Journal, Vol.41, PP392, May 2008 [4] H. Djeghloud, A. Bentounsi and M. Larakeb, “Real and virtual labs for enhancing an SM course”, 15th Intern. Conf. on Electrcial Machines and Systems (ICEMS 2012), Sapporo, Japan, 21-24 Oct. 2012 [5] F. Saadi and K. Zellagui, “Virtual laboratory of a DC machine”, Engineer Report, ED-UMC, Algeria, June 2011. [6] National Instruments, “NI USB6008 Guide Manual” [7] Riccardo de Asmundis, “LabVIEW-Modeling, Programming and Simulations” InTech Publication, 2011. [8] National Instruments, “LabVIEW User Manual” [9] National Instruments, “LabVIEW Simulation Interface Toolkit User Guide”. [10] D.P. Kothari,“ Laboratory Manuals for Electrical manuals Machines”, I.K. International Publishing, 2013.

Design and Development of Power Quality Monitoring and Analysis System Based on LabVIEW Ajit Singh

Lini Mathew

Lecturer, Deptt. of Electrical Engg., GBN Govt. Polytechnic, Nilokheri, India e-mail: [email protected]

Associate Professor, Deptt of Electrical Engg., NITTTR, Chandigarh, India e-mail: [email protected]

Abstract—This paper discusses the design of a power quality analyzer based on LabVIEW. In this paper, design of hardware as well as software has been discussed. The developed PQ analyzer has then been used to perform power quality analysis on two absolutely different kinds of loads i.e. resistive load and a power rectifier load. The designed power quality analyzer has a unique load protection feature which can be used to protect any three phase electrical load from damage, in case of poor power quality condition. The LabVIEW software platform is used for designing software algorithm for computation and display of power quality parameters. The use of LabVIEW as a platform has many advantages over physical instruments. Keywords: Power Quality, Power Quality Analyzer, LabVIEW, Virtual Instrumentation, Harmonic Analyzer

I.

INTRODUCTION

Modern world is heavily dependent on the constant and reliable availability of electrical power supply. Now the quality of this power supply is becoming more important due to increasing sensitivity of the equipment and devices used by the customers. A decrease in supply voltage for a fraction of a second can trip a microprocessor-based controller offline, disrupting an entire manufacturing process. Due to the above factors, power quality monitoring has been of great concern for consumers as well [1]. The system disturbances, which were tolerated earlier, may now cause interruption to industrial power system with a resulting loss of production. In order to evaluate and identify the disturbances and their origin, power quality monitoring is a tool that utilities and customers must use [2]. Now a days, work is going on for development of efficient and cost effective way to monitor and analyse power quality. The proposed method of power quality monitoring is by using LabVIEW software along with data acquisition hardware. The developed PQ analyzer can be used for monitoring and analysis of the power quality problems so that some optimal solution can be applied.

II.

POWER QUALITY

Ideally, the best electrical supply would be a constant magnitude and frequency sinusoidal voltage waveform. The Power Quality of a system expresses to which degree

a practical supply system resembles the ideal supply system. Power quality determines the fitness of electrical power to consumer devices. Without proper power, an electrical device (or load) may malfunction, fail prematurely or not operate at all. Power quality is defined in the IEEE 100 Authoritative Dictionary of IEEE Standard Terms as: The concept of powering and grounding electronic equipment in a manner that is suitable to the operation of that equipment and compatible with the premise wiring system and other connected equipment [3]. From customer frame of reference, the power quality problem may be defined as: Any power problem manifested in voltage, current, or frequency deviations that result in failure or malfunction of customer equipment [4].

III. DESIGN OF HARDWARE FOR POWER QUALITY ANALYZER The voltage and current signals, for which power quality is to be monitored, are interfaced to the computer using transducers and data acquisition (DAQ) card.

A. Data Acquisition In the PQ monitoring system developed, the DAQ card used is NI PCI 6251 from National Instruments. The main features of this DAQ card includes a sampling rate 1.25 MS/s, 16 analog inputs having 16 bit resolution, 2 analog outputs, 24 digital input outputs channels, Maximum analog input voltage range 10V, On board memory 4095 samples, Input impedance >10 GΩ in parallel with 100 pF etc.

B. Voltage Transducers Keeping in view the fact that the PQ analyzer has to operate in poor power quality conditions including swell, overvoltage and impulsive conditions, two potential transformers (PT) of rating 220V/9V are connected in series, making it capable to withstand 440V rms per phase in total. The overall rating of P.T. comes out to be 440V/9V.


C. Current Transducers Three C.T. are used in the PQ analyzer having the current rating 25A/5A each. The current output of C.T. is converted into voltage signal by passing the secondary output current of C.T. through a resistance of 0.5Ω, 20W each. With this configuration, 25A current signal is converted into a voltage signal of 2.5V (rms) which is then fed to DAQ card for measurement.

The developed PQ analyzer can take three phase voltages and currents as input. The algorithm developed in LabVIEW software processes the voltage and current data and displays various results on front panel of the PQ analyzer. Fig. 2 shows the setup used for taking various readings. The P.T. are connected to the three phase voltage line and three phase load is connected through C.T.

D. Electromagnetic Contactor The PQ analyzer has been designed such that it can be used for protection of any sensitive load from many PQ problems such as over voltage, under voltage, over current, over THD, over frequency, under frequency etc. For this purpose, a triple pole with neutral (TPN) electromagnetic contactor is used in PQ analyzer having a rating of 415V, 25A on load side

E. Solid State Relay

Fig. 2: Setup Used for Power Quality Analysis

To control the contactor, a thyristor based solid state relay is used. One of the digital outputs of DAQ card is used to trigger the solid state relay and thus control the energizing coil of the contactor. The solid state relay, used, has 330V ac, 10A rating on the output side and has a triggering voltage rating of 3 to 32V dc.

To evaluate the performance of the developed PQ analyzer, the author has taken readings with two absolutely different load conditions. The two different kinds of loads which have been used for evaluating the performance of the PQ analyzer are as under:

Figure 1 shows the complete circuit diagram of power quality analyzer developed.

Three Phase Resistive Load: A three phase rheostatic load of rating 1.5 kW per phase with line voltage rating of 400V was used. Three Phase Rectifier Load: The power converting devices are the main cause of harmonic pollution in the power system. To investigate this, it was decided to evaluate the PQ analyzer with a three phase rectifier load. The three phase rectifier used for this purpose was a three phase 400V ac to 250V, 50A dc rectifier. A dc shunt motor having rating 1kW, 200V dc was used as a load on the rectifier.

IV. LABVIEW BASED SOFTWARE AND ITS EVALUATION FOR POWER QUALITY ANALYSIS Being deemed as a standard data acquisition and instrument control software, LabVIEW is not only an innovative software product, but also is an integrated environment concerning graphical software development which is most widely used, develops faster and has the strongest functions [5]. The LabView environment contains pre-installed drivers for a variety of measurement devices. The configuration of devices is in most cases done without user help [6]. The hardware described above is

Fig. 1: Complete Circuit Diagram of Power Quality Analyzer

interfaced with the three phase power supply line and readings are taken by connecting different three phase loads one by one. According to standard IEC 61000-4-

Design an nd Developmentt of Power Quality Monitoring and a Analysis Sysstem Based on LabVIEW  25 5

3:2002, the power p qualityy parameter magnitudes m (suupply voltage, harm monics, interhaarmonics andd unbalance) are a to be calculated for 10-cycle time interval for a 50 Hz power p system. The DAQ D assistannt express VI which is useed for importing reaal time voltagee and current data is configgured for importing 10 cycle dataa at a time.

TABLE I: VOLTAGE O AND FREQ QUENCY MEASUR REMENT READINGS E FOR RES SISTIVE LOAD

A Voltage Measuremennt A. The rms value of wavve is computted by addingg rms value of indivvidual harmonnic wave, as giiven in eqn. (11). Vrms= ∑ √

√

phase resistive loaad and three pphase rectifierr load. Table I and Table T II show ws various volltage measurem ment readingss taken n with resistiive and rectiffier load for all the threee phases. It is obserrved that the nnon fundamen ntal part of thee voltaage is less wiith resistive looad and is mu uch high withh rectiffier load. Thhis is due too the fact that the powerr conv verting loads innject harmoniics in the supp ply system.

=

⋯

(1)

where Vh is the peaak value of the waveforrm at harmonic com mponent h.

Measured d Factor RMS S Voltage (V) Fund damental RMS Voltage (V) Non Fundamental RM MS Voltage (V) Peak k Voltage (V) RMS S Voltage Deviatiion (%) Freq quency (Hz) Freq quency Deviation (%)

V1 224.77 224.58 9.28 309.51 -2.27

V2 224.72 2 224.69 2 3.58 320.57 3 -2.29 50.03 5 0.070 0

V3 229.36 229.05 11.76 324.01 -0.27

TABLE II: VOLTAGES AND FREEQUENCY MEASU UREMENT READINGS E FOR REC CTIFIER LOAD Measured d Factor RMS S Voltage (V) Fund damental RMS Voltage (V) Non Fundamental RM MS Voltage (V) Peak k Voltage (V) RMS S Voltage Deviatiion (%) Freq quency (Hz) Freq quency Deviation (%)

V1 211.11 192.28 87.13 395.09 -8.21

V2 218.54 2 199.35 89.56 8 412.89 4 -4.98 49.94 4 -0.11 -

V3 206.43 188.71 83.65 386.49 -10.24

B. Voltage Wavveforms Fig. 3: Volttage Measuremennt

Figure 3 shows the front f panel GUI G developed for measurement of three phhase voltages. The indiccators indicate RMS S phase voltagges, Fundameental rms volttages, Peak voltagees, Non Funddamental volltages, Frequency, Voltage and Frequency F devviations in refference to stanndard voltage and frrequency.

Fig. F 5 shows the three phaase voltage waaveforms withh rectiffier load. It can c be observved that the waveforms w aree not pure p sine wavves. Some noon fundamenttal signals aree superimposed on o these. The non fundamentall superimposed siggnal is considderably high with rectifierr load.. This is due to nonlinear beehaviour of th he diodes usedd for rectification. r T waveform The ms observed with resistivee loadss were almostt pure sine wavves.

Figure 4 shows thhe block diiagram algorrithm developed forr voltage meassurement.

Fig. 5: Voltage Waveforms W with Three Phase Recctifier Load

C. Current Meaasurement Fig. 4: Block Diagram m for Voltage Meeasurement

The devveloped PQ analyzer has been usedd for measurement of voltage components c o supply system. of The measurem ments of volttage have beenn taken with three

Figure F 6 shoows the front panel GUI developed d forr curreent measurem ment. Measurred values of current aree RMS S currents, Fundamentaal rms cu urrents, Nonn fundamental rms currents c and P Peak rms curreents.


E. Harmonic H Analysis Figure F 8 shoows the front panel GUI developed d forr displlay of differeent data relateed to harmonics present inn the voltage v wavefo form.

Fig.. 6: Three Phase Load L Current Meeasurement

A push button b has beeen provided to switch ON O or OFF the three phase load connected. The T boolean output o of push buttoon is passed to t the solid state s relay thrrough digital outputt of the DAQ card. c TABLE III: CUR RRENT MEASUREM MENT READINGS FOR VARIOUS LOADS O Measu ured Factor RMS Current (A A) Fundamental RM MS Current (A) Non Fundamenttal RMS Current (A) Peak Current (A A)

Resistive Load L I1 I2 I3 5.88 6.07 6.26 5.87 6.06 6.25 0.34 0.28 0.23 8.82 8.76 9.38

Rectifier Load I1 I2 I3 3.27 3.26 3.06 3.15 3.14 2.93 0.86 0.84 0.89 5.33 5.03 5.44

The meaasurements off current havve been takenn for three phase resistive r load and three phhase rectifier load. Table III shoows various current meassurement readdings taken with reesistive and rectifier loadd for all the three phases.

D. Current Waveform Figure 7 shows the three t phase current c wavefforms with rectifierr load. It cann be observedd that the cuurrent waveforms foor rectifier looad are very far f away from m the pure sine wavve.

Fig. 8: Harm monic Analysis D Data with Resistiv ve Load

The harmoniic data is ddisplayed in the form off harm monic bar chaart, harmonicc waveform, and numericc array y indicator. Thhe Total Harm monic Distortiion (THD) forr all three t phases is also dissplayed according to EN N 5016 60:2007. Thee THD is a measure of the potentiall heatiing value of thhe harmonics relative to thee fundamental. THD D is the ratio of total effective value of the harmonicc wavees to the effecctive value of base wave co omponents [7]. This index can bee calculated foor either voltaage or currentt by ussing eqn. (2). THD =

∑

(2))

where w Mh is the t rms valuee of harmonic component h of th he quantity M. M Table IV shhows the read dings of Totall Harm monic Distortiion (THD) in voltage for alll three phasess A, B and C, for resistive and recctifier loads. TABLE IV V: TOTAL HARMO ONIC DISTORTION N IN VOLTAGE O FOR DIFF FERENT LOADS Measured M Factorr THD D Phase A (%) THD D Phase B (%) THD D Phase C (%)

Resistive Load 3.558 2.555 4.776

Reectifier Load 45.09 44.90 44.11

F. Unbalance Analysis A of V Voltage and Current C Fig. 7: Load Current Waveforms W with Rectifier R Load

This is due d to non linear l behavioour of the diodes present in thhe rectifier. This behavioour of the power p converters acttually injects harmonics in the power system. The waveform ms observed with resistive loads weree sine waves with soome deformattions superimpposed.

According A too IEC 610000-4-30:2008, the voltagee unbaalance is givenn by eqn. (3) aand (4)

Design an nd Developmentt of Power Quality Monitoring and a Analysis Sysstem Based on LabVIEW  27 7

G. Impulse I Monnitoring The front panel GUI developed for impulsee moniitoring is shoown in Fig. 111. In this GU UI a numericc contrrol is provvided to sett peak imp pulse voltagee thresshold value.

Fig. 9: Front Panel for Voltagge and Current Unbalance U Analysis

Figure 9 shows the front panel GUI G designedd for analysis of unbalance u in three t phase vooltage and cuurrent waveforms. The numericcal indicators are provideed to of Volttages, display syymmetrical components Fundamental Voltages, Currents and a Fundam mental Currents. Thhe numeric inndicators are also provideed to display the percentage of unbalaance in volltage, fundamental voltage, v curreent and fundam mental currentt.

Fig. 11: Front Panel for IImpulse Monitoriing

Based B on thhe threshold value set, th hree numericc indiccators indicatee the number of impulse in ncidents foundd in current c samplle of 10 cyycle data. Numeric N arrayy indiccators have been b providedd, for all three phases, too indiccate the samplle location, peeak amplitudee and rise timee of th he impulses deetected. This V VI also gives measurements m s of th he second derrivative of thee amplitude at a each of thee peak ks found in the current block of data. Secondd deriv vatives give ann approximate measure of the sharpnesss of eaach peak.

H. Load L Protecction Fig. 10: Blockk Diagram for Volltage and Currentt Unbalance Anallysis

Figure 100 shows the block b diagram m algorithm. Inn this block diagram m, Spectrum VIs V are used too compute thee FFT spectra of inpput voltage annd current wavveforms. Thesse VI returns FFT spectra as coomplex specttra of voltagee and current, up to t a harmoniic order speccified as 50. The complex specctra are given to Symmetriccal Componennts VI which compuutes the voltage and cuurrent symmeetrical components for f a 10-cycle block. Table V shows the level of unbalance in percentagee for voltage and a current siggnals. h in casse of It is evidentt that the unnbalance is highest rectifier load.

To make thiss PQ analyzerr practically more m useful, a load protection feature f has aalso been ad dded. As thee deveeloped PQ anaalyzer can be uused for analy ysis of voltagee and load l current inn situations w where power qu uality is reallyy poorr, the added protection feature may giive it anotherr dimeension. Most of o the industriial machines used u now dayss are microprocessor based whhich require good qualityy poweer. The protecction feature ttakes care of such sensitivee loadss. It switches off poor quallity power so that it can bee put on any alterrnate good qquality powerr source likee UPS etc.

TABLE V: UNBALANCE N IN VOLTAGE O AND CUR RRENT WAVEFORM MS Componen nt Zero Sequence Unbalance (%) Negative Sequeence Unbalance (%) Fundamental Zeero Sequence Unbaalance (%) Fundamental Negative Sequeence Unbalance (%)

Resistive Rectifier Load Load Voltagee Unbalance

Resistive Recttifier R Looad Load Current Unbalaance

4.11

44.99

3.61

3.559

1.87

2.03

2.88

22..41

2.18

2.50

2.66

1.888

1.42

1.15

2.13

2.15

Fig. 12: Front Panel foor Load Protection n

Figure F 12 shoows the frontt panel GUI developed d forr threee phase loadd protection. The protectiion has beenn


provided for high voltage, low voltage, high frequency, low frequency, over current and high THD in voltage. Here sliders have been provided to set the threshold values for each of the protection variable. Six LEDs have been provided to indicate the protection variable which crosses its limit. A push button has been provided to enable or disable this protection feature of PQ analyzer.

V. CONCLUSION In this paper the author has discussed the step by step procedure adopted to design the hardware and software of a PQ analyzer. Relevant software has also been developed using LabVIEW for real time monitoring and analysis of power quality problems in power system. The developed power quality analyzer has a unique three phase load protection feature. As the designed PQ analyzer is based on virtual instrumentation principle, it is highly configurable. The main features of developed PQ analyzer include wide range of voltage and current, user friendly GUI, real time data processing, portable, data saving capabilities etc. Two absolutely different kinds of three phase electrical loads viz. Resistive Load and Rectifier Load have been analysed for power quality parameters. From the above analysis it is observed that the rectifier load injected a lot of harmonics in the power line due to non linear behaviour of the power electronics components. This has been verified by THD values observed.

REFERENCES [1]

[2]

[3]

[4] [5]

[6]

[7]

Shahedul Haque Laskar, Mohibullah Muhammad, “Power Quality Monitoring by Virtual Instrumentation using LabVIEW”, Proceedings of the 46thInternational Universities' Power Engineering Conference- UPEC 2011, Soest, Germany, September, 2011. S.K. Bath, Sanjay Kumra, “Simulation and Measurement of Power Waveform Distortions using LabVIEW”, Proceedings of the 26th International Power Modulator Symposium and 2008 High Voltage Workshop, Las Vegas, Nevada, May, 2008. S. Khalid, Bharti Dwivedi, “Power Quality Issues, Problems, Standards and their Effects in Industry with Corrective Means”, International Journal of Advances in Engineering & Technology, Vol. 1, Issue 2, pp.1-11, May 2011. Roger C. Dugan, Mark F. McGranaghan, Surya Santoso, H. Wayne Beaty, “Electrical Power Systems Quality”, A Text Book, Tata McGraw Hill Education Private Ltd, Third Edition, 2013. Wang Shenghui, Jin Xing, “Design of Power Quality Monitoring System based on LabVIEW”, Proceedings of the 2nd International Conference on Computer Application and System ModelingICCASM 2012, Shenyang, China, July, 2012. J. Esim, I.J. Oleagordia, S. Loureiro, “Research and Development of a Virtual Instrument for Measurement, Analysis and Monitoring of the Power Quality”, Proceedings of International Conference on Renewable Energies and Power Quality (ICREPQ’13), Bilbao (Spain), March, 2013. Jing Chen, Tianhao Tang, “Power Quality Analysis Based on LabVIEW for Current Power Generation System”, Proceedings of the International Symposium on Power Electronics, Electrical Drives, Automation and Motion-SPEEDAM 2012, Sorrento (Italy), June, 2012.

Transformer Fault Diagnosis Based on DGA Method Using Classical Methods Pushpanjali Singh Bisht

Arrik Khanna

Assistant Professor, EEE, RVS College of Engineering and Technology, Jamshedpur, India e-mail: [email protected]

Assistant Professor, EEE ,Chitkara University, Punjab Campus, India e-mail: [email protected]

Deepak Student, EEE, RVS College of Engineering and Technology, Jamshedpur, India e-mail: [email protected] Abstract—During the last few years there has been trend of continuous increase in transformer failures. It is therefore necessary to diagnose the incipient fault for safety and reliability of electrical network. Various faults could occur in transformer such as overheating, partial discharge and arching which can generate various fault gases so in order to diagnose the fault DGA (Dissolved gas Analysis) is done. In this paper the proposed methods are used which is based on standards and guidelines of International Electro technical Commission (IEC), Central Electric Generating board (CEGB), and the American Society for testing and Material (ASTM). Fault diagnoses methods by the DGA technique are implemented to improve the interpretation accuracy of transformer. Keywords: Dissolved Gas Analysis (DGA), Central Electric Generating Board (CEGB), The American Society for Testing and Material (ASTM), Institute of Electrical and Electronics Engineering (IEEE), International Electro Technical Commission (IEC), British Standard (B.S.), Decomposition (Decomp)

I.

INTRODUCTION

Transformers are the essential part of the electrical power system because it has the ability to alter voltage and current levels, which enables the power transformer to transmit and distribute electric power and utilize the power at economical and suitable levels. In electrical power system, voltage of electricity generated at the power plant will be increased to a higher level with step-up transformers. A higher voltage will reduce the energy lost during the transmission process of the electricity. After electricity has been transmitted to various end points of the power grid, voltage of the electricity will be reduced to a usable level with step-down transformer for industrial customers and residential customers. Since power transformer is vital equipment in any electrical power system, so any fault in the power transformer may lead to the interruption of the power supply and accordingly the financial losses will also increase. So it is of paramount importance to detect the incipient fault of transformer as early as possible. The following characteristics of oil were laid down in B.S.148:1959 the values stated being obtained by the testing method specified in the, appendices of the standard.

TABLE 1: PHYSICAL PROPERTIES OF TRANSFORMER OIL Characteristic Sludge Value(max) Acidity after oxidation(max) Flash Point (closed) (min) Viscosity at 70°F(21.1°C)(max) Pour Point (max) Electric Strength, 1 minute (min) Acidity(neutralization value) Total (max) Inorganic Saponification Value (max) Copper discoloration Crackle Specific gravity

Limit 1.20% 2.5 mg KOH/gm 295° F (146.1°C) 37 cS (-25.06°F) (-31.7°C) 40 kV (r.m.s) 0.05mg. KOH/gm Nil 1.00 mg. KOH/gm Negative Shall pass test No Limit

Faults can be differentiated for their energy, localization and occurrence period. Along with a fault, there are increased oil temperatures and generation of certain oxidation products such as acids and soluble gases. These gases, hydrogen ( H2), methane ( CH4 ), ethane ( C2H6 ), ethylene ( C2H4 ), acetylene ( C2H2 ), propane ( C3H8 ), propane ( C3H6 ), together with carbon monoxide ( CO ) and carbon dioxide ( CO2 ) are considered as fault indicators and can be generated in certain. The operating principle of transformer is based on the slight albeit harmless deterioration of the insulation that accompanies incipient faults, in the form of arcs or sparks resulting from dielectric breakdown of weak or overstressed parts of the insulation, or hot spots due to abnormally high current densities or due to high temperature in conductors. Whatever the cause, these stresses will result in the chemical breakdown of oil or cellulose molecules constituting the dielectric insulation

II.

DISSOLVED GAS ANALYSIS

Thermal and electrical distributions in the operating transformer are two most important causes of dissolved gases in oil. The gases produced from thermal decomposition of oil and solid insulation are because of losses in conductors due to loading. Also decomposition occurs in oil and solid insulation is due to occurrence of arc. In case of electrical disturbances the gases are formed principally by ionic bombardment. The gases are generated mainly because of cellulose and oil insulation deterioration. In the normal operation of the transformer, gases such as Hydrogen (H2), Methane (CH4), Ethylene


(C2H4), Acetylene (C2H2), and Ethane (C2H6) and so on are released. In the existing methods, parts per million (PPM) values are determined for each gas in the oil along with a total value of combustible gasses. When there is an abnormal situation such as a fault occurrence, some specific gases are produced in greater quantity than in the normal operation. Thus, the amount of these gases in the transformer oil increases. The increase in the amount of gases results in saturation of the transformer oil and no further gas can be dissolved in oil. Therefore, when the oil is saturated, the gas is released from the oil. The amount of the dissolved gas is related to the temperature of the oil and the type of gas. The produced gas can be classified into three groups: polarization, corona, and arcing. These groups coming from the severity of the released energy during the fault are different. The largest and lowest amounts of the released energy are associated with the arcing and corona.

TABLE 3: FAULT DIAGNOSIS IEC CODES Sl. No. 1 2

X 0 0

Code Y Z 0 0 1 0

3

1

1

4

0

5

1 or 2 1

0

2

6

0

0

1

7

0

2

0

8

0

2

1

9

0

2

2

Kind of Fault

Grouping of Fault No fault F1 Partial discharge with low F2 intensity discharge 0 Partial discharge with F3 high intensity discharge 1 or 2 Partial discharge with low F2 intensity discharge Partial discharge with high intensity discharge Thermal fault with temperature less than 150°C Thermal fault with temperature between 150° C to 300° C Thermal fault with temperature between 300 °C to 700° C Thermal fault with temperature greater than 700°C

a. Polarization: In the transformer oil, the released gases at low temperature are CH4 and C2H6, and at high temperature are C2H6, CH4, C2H4, and H2. In cellulose, the generated gases at low and high temperatures are CO and CO2.

b. Corona: In corona, the produced gas in oil is H2 and the released gases in cellulose are H2, CO, and CO2.

c. Arcing: In this case, the released gases are C2H6,

Roger’s Ratio Method

Gas Ratio W=CH4/H2

Value W700°C

0 2

2

Thermal fault with temp >700°C

0 2

2


0 2

2


0 2

2


0 2

2


0 2

2


0 2

1

Thermal fault with temp bet. 300°C & 700°C

TABLE 13: FAULT DIAGNOSE BY DOERNENBURG RATIO

Sl. No 1 2 3 4 5 6 7 8 9

Doernenburg Ratio Ratio O P

M

N

0.561 2.8427 1.2869 1.9281 2.1564 1.3655 1.3897 1.0982 2.2707

0 0.0201 0.0203 0.0009 0.0019 0.0176 0.0377 0.0342 0

N.R 15.0427 13.8571 251.6 115.45 8.7664 4.23444 5.85123 N.R

0 0.02312 0.02167 0.00187 0.00373 0.10996 0.14744 0.09901 0

Fault Transformer Fault Diagnosis Thermal Decomp Thermal Decomp Thermal Decomp Thermal Decomp Thermal Decomp Thermal Decomp Thermal Decomp Thermal Decomp Thermal Decomp

III. CONCLUSION In this paper the analysis of dissolved gas of transformer is used to diagnose the fault in the transformer using Rogers’s ratio through IEC, CEGB, ASTM standards parallel with DUVAL triangle and Doernenburg method. These techniques are implemented for better decision on the power transformer state and classification of power transformer fault using dissolved gas analysis as input data. It is presented here that how one technique is superior over the other for diagnosing the fault of the transformer in the most convenient manner. This shows great promise in that a number of faults likely to cause future trouble in service have been detected, although in each case the transformer had satisfactorily passed the routine tests. The technology presently exists and is being used to detect and determine fault gases below the part per million levels. However there is still much room for improvement in the technique, especially in developing the methods of interpreting the results and correlating them with incipient faults.

Transformer Fault Diagnosis based on DGA Method Using Classical Methods  33

REFERENCES [1]

[2]

[3]

[4]

[5]

IEEE Std C57.104-199, 1992, "IEEE Guide for the Interpretation of Gases Generated in Oil Immersed Transformers". IEEE Press, New York Rogers R. R., 1978, "IEEE and IEC code to interpret incipient faults in transformers using gas in oil analysis ", IEEE transaction electrical Insulation.,,Vo.13,No.5, 349-354 DiGiorgio, J.B. (2005) “Dissolved Gas Analysis of Mineral Oil Insulating Fluids. DGA Expert System” A Leader in Quality, Value and Experience 1, 1-17 Dornerburg, E. and Strittmatter, W, “Monitoring oil cooling transformers by gas analysis”, Brown Boveri Review, vol61, May 1974, pp. 238-247. Duval, M., 1989, "Disssolved gas analysis, It can save your transformer", IEEE Electrical Insulation Man., Vo.5, No.6, 22-27.

[6]

[7]

[8] [9]

Gradnik, K. M., “Physical-Chemical Oil Tests, Monitoring and Diagnostic of Oil-filled Transformers.” Proceedings of 14th International Conference on Dielectric Liquids, Austria, July 2002 Haupert,T. J., Jakob, F., and Hubacher, E. J., 1989, "Application of a new technique for the interpretation of dissolved gas analysis data" 1lth Annual Technical Conference of the International Electrical Testing Association, 43-51. Herbert G. Erdman (ed.), Electrical insulating oils, ASTM International, 1988 ISBN 0-8031-1179-7, p.108. Hooshmand R., Banejad M., 2006 "Application of Fuzzy Logic in Fault Diagnosis in Transformers using Dissolved Gas based on Different Standards", World Academy of Science, Engineering and Technology,No.17.

Sustainable Electric Power Systems through PSDF Tanya Navin Kohli Vth Sem. Power System Engg, Dept of Electrical Engg., University of Petroleum and Energy Studies, Dehradun, India e-mail: [email protected] Abstract—Our country has been seeing major concerns of Power System Design and Operation (PSDO) in respect of Quality, Reliability, Security, Stability and Economy (QRSSE). The quality means continuous at desired frequency and voltage level. The reliability means minimum failure rate of components and systems. The security means robustness i.e. normal state even after disturbances. The stability means maintain synchronism under disturbances. The economy means minimize Capital, running and maintenance Costs. There is a strong need for Power System Management considering demand for power increasing every day. Strengthening number of transmission line, Sub-stations, Transformers, switchgear etc. Managing operation and interaction as it is becoming more and more complex. It is essential to monitor simultaneously for the total system at a focal point i.e. Energy Load Centre or Load Dispatch Centre. These all management requires huge fund for strengthening and implementation of the issues related to power system. For this, Government of India has taken initiative and launched a scheme called operationalisation of Power System Development Fund (PSDF). The PSDF shall be utilized for the strengthening of power system as a whole considering all aspects. The paper intended to express the various ways of management of PSDF. The paper also endeavors to see the implication of operationalization of Power System Development Fund (PSDF) and utilization of this fund. Keywords: Power System, Quality, Reliability, Security, Stability, Economy, Power System Management and Power System Development Fund.

I.

Why were earlier utilities the ‘monopolies'? The reason for monopoly can be traced right back to the early days when electricity was comparatively a new technology. The skeptical attitude of the government towards electricity led to investment by private players into the power sector, who in turn, demanded for the monopoly in their area of operation. This created a winwin situation for both- government and the electrical technology promoters. However, the government would not let the private players enjoy the monopoly and exploit the end consumer and hence introduced regulation in the business. Thus, the power industries of initial era became regulated monopoly utilities. The structure of a conventional vertically integrated utility is shown in Fig. 1.1. As evident from the figure, there was only a single utility with whom the customer dealt with. Thus, only two entities existed in the power business: a monopolist utility and the customer. Generation

Transmission

Distribution

INTRODUCTION

The power industry across the globe is experiencing a radical change in its business as well as in an operational model where, the vertically integrated utilities are being unbundled and opened up for competition with private players. This enables an end to the era of monopoly. Right from its inception, running the power system was supposed to be a task of esoteric quality. The electric power was then looked upon as a service. Control consisting of planning and operational tasks was administered by a single entity or utility. The vertical integration of all tasks gave rise to the term vertically integrated utility. The arrangement of the earlier setup of the power sector was characterized by operation of a single utility generating, transmitting and distributing electrical energy in its area of operation. Thus, these utilities enjoyed monopoly in their area of operation. They were often termed as monopoly utilities. [1]

Customer Power Flow Money Flow Fig: 1.1: Vertically Integrated Utility

II.

ELECTRIC POWER SYSTEM

Electric power systems are real-time energy delivery systems. Real time means that power is generated, transported, and supplied the moment you turn on the light switch. Electric power systems are not storage systems like water systems and gas systems. Instead, generators produce the energy as the demand calls for it. [2]

Sustainable Electric Power Systems through PSDF  35

B. Power Quality Issues In view of this there are steps to address Power Quality issues, they are: 

Detailed field measurements



Monitor electrical parameters at various places to assess the operating conditions in terms of power quality.



Detailed studies using a computer model. The accuracy of computer model is first built to the degree where the observed simulation values matches with those of the field measurement values. This provides us with a reliable computer model using which we workout remedial measures.



For the purpose of the analysis we may use load flow studies, dynamic simulations, EMTP simulations, harmonic analysis depending on the objectives of the studies.



We also evaluate the effectiveness of harmonic filters through the computer model built, paying due attention to any reactive power compensation that these filters may provide at fundamental frequency for normal system operating conditions.



The equipment ratings will also be addressed to account for harmonic current flows and consequent overheating.

Fig. 1.2: Electric Power System Overview (source: S.W. Blume-2007)

A. Power Quality Power quality is characterized by [3]: 



Stable AC voltages at near nominal values and at near rated frequency subject to acceptable minor variations, free from annoying voltage flicker, voltage sags and frequency fluctuations. Near sinusoidal current and voltage wave forms free from higher order harmonics

All electrical equipments are rated to operate at near rated voltage and rated frequency. There are various effects of Poor Power Quality which are: 

Maloperation of control devices, relays etc.



Extra losses in capacitors, transformers and rotating machines



Fast ageing of equipments



Loss of production due to service interruptions



Electro-magnetic interference due to transients



power fluctuation not tolerated by power electronic parts

Some of the major causes of Poor Power Quality are: 

Nonlinear Loads



Adjustable speed drives



Traction Drives



Start of large motor loads



Arc furnaces



Intermittent load transients



Lightning



Switching Operations



Fault Occurrences

C. Power Quality Solution Poor power quality in the form of harmonic distortion or low power factor increases stress on a facility’s electrical system. Over time this increased electrical stress will shorten the life expectancy of electrical equipment. In addition to system degradation, poor power quality can cause nuisance tripping and unplanned shutdowns within electrical system. [4] In an increasingly automated electrical world, it is important for a facility to evaluate power quality. Harmonic distortion, low power factor, and the presence of other transients can cause severe damage to electrical system equipment. PSE provides system analysis and evaluation of power quality issues and makes recommendations for system design solutions.

D. Structure of PowerSystem Generating Stations, transmission lines and the distribution systems are the main components of an electric power system. Generating stations and distribution systems are connected through transmission lines, which also connect one power system (grid, area) to another. A distribution system connects all the loads in a particular area to the transmission lines.


For economical technical reasons, individual power systems are organized in the form of electrically connected areas or regional grids. Major Concerns of Power System Design and Operation are: 

Quality: Continuous at desired frequency and voltage level



Reliability: Minimum failure rate of components and systems



Security: Robustness - normal state even after disturbances



Stability: Maintain disturbances



Economy: Minimize maintenance Costs.

synchronism Capital,

under

running

2. Installation

of shunt capacitors, series compensators and other reactive energy generators for improvement of voltage profile in the grid.

3. Installation of standard and special protection schemes, pilot and demonstrative projects, and for setting right the discrepancies identified in protection audits on regional basis.

4. Renovation and Modernization (R&M) of transmission and distribution relieving congestion.

above objectives, such as, conducting technical studies and capacity building, etc. Projects proposed by distribution utilities in the above areas that have a bearing on grid safety and security, provided these are not covered under any other scheme of the Government of India, such as Restructured-Accelerated Power Development and Reforms Programme (RAPDRP)/Rajiv Gandhi Grameen Vidyutikaran Yojana (RGGVY)/National Electricity Fund (NEF), etc. will be eligible under this scheme. Private sector projects would not be eligible for assistance from the Fund.

Today, there is a need for “Power System Management” are: Demand for Power Increasing every day



No of transmission line, Transformers, switchgear etc.,



Operation and Interaction is more and more complex



Essential to monitor simultaneously for the total system at a focal point-Energy Load Centre.

Sub-stations,

As power systems increased in size, so did the number of lines, substations, transformers, switchgear etc. Their operation and interactions became more complex and hence it is necessary to monitor this information simultaneously for the total system at a focal point called as energy control centre. The fundamental design feature is increase in system reliability and economic feasibility.

III. POWER SYSTEM DEVELOPMENT FUND These all management of power system requires huge fund for strengthening and implementation of the issues. For this regard, Government of India has taken initiative and launched a scheme called operationalisation of Power System Development Fund (PSDF) vide its notification dated 10.01.2014. [5] The Power System Development Fund shall be utilized for the strengthening of power system. The details of the criteria and purpose for which the Power System Development Fund will be utilized are as follows:

In the Lok Sabha Parliamentry Question no 337, answered on 13.2.2014, GoI intimated that Govt has approved the scheme for operationalisation of Power System Development Fund and as on 31.12.2013, the total fund available with PSDF is Rs 6300 Crore. [6] Central Electricity Regulatory Commission, New Delhi on 09.06.2014 has notified the regulations called the “Central Electricity Regulatory Commission (Power System Development Fund) Regulations 2014”. [7]

A. PSDF Regulation There shall be constituted a fund to be called the “Power System Development Fund” or "PSDF" and there shall be credited there to: 

Congestion charges standing to the credit of the “Congestion Charge Account” after release of amounts payable to Regional Entities entitled to receive congestion charges along with interest, if any, in accordance with the Congestion Relief Regulations;



Congestion amount arising from the difference in the market prices of different regions as a consequence of market splitting in power exchanges in accordance with Power Market Regulations;



Deviation Settlement Charges standing to the credit of the "Regional Deviation Pool Account

1. Creating necessary transmission systems of strategic importance based on operational feedback by Load Dispatch Centres for relieving congestion in Inter-State Transmission Systems (ISTS) and intra-state system which are incidental to the ISTS.

for

5. Any other scheme / project in furtherance of the

and



systems


Fund" after final settlement of claims in accordance with Deviation Settlement Mechanism Regulations; 

RLDC reactive energy charges standing to the credit of Reactive Energy Charges Account in accordance with the Grid Code;



Additional Transmission Charges arising out of the explicit auction process in STOA Advance Bilateral transactions in accordance with the CERC (Open Access in interstate transmission) Regulations, 2008 and amendments thereof;



Such other charges as may be notified by the Central Commission from time to time.

The agencies which are authorized to collect Congestion charges, Congestion amount, Deviation Settlement charges, Reactive energy charges under the respective regulations and such other charges as may be notified by the Commission from time to time, shall transfer to the credit of the Fund the balance amounts in the charges under sub-clauses (a) to (f) of clause (1) of this regulation on monthly basis or on such periodicity as may be provided in the Detailed Procedure. The PSDF shall be maintained and operated through the Public Account of India. All the amounts that would accrue into the fund as per clause (1) of Regulation 3 and also the amounts lying accumulated in the fund and not transferred to public account till the issue of this regulation, shall be transferred to the Public Account of India.

B. Utilisation of PSDF



Renovation and Modernization (R&M) transmission system for relieving congestion.



Any other scheme/ project in furtherance of the above objectives such as technical studies, capacity building, installation of Phasor Measurement Unit (PMU) etc.

PSDF shall also be utilized for the projects proposed by distribution utilities in the above areas which are incidental to inter-state transmission system and have a bearing on grid safety and security, provided that these projects are not covered under any other scheme of the Government of India, such as Restructured Accelerated Power Development & Reforms Programme (RAPDRP), Rajiv Gandhi Grameen Vidyutikaran Yojana (RGGVY) / National Electricity Fund (NEF) etc. The private sector projects shall not be eligible for assistance from PSDF. Prioritization shall be done mainly on the criteria of the schemes (i) addressing grid security concerns; (ii) being of national importance; (iii) being in the order of National/Multi utility/Regional/State importance; (iv) being inter-state in nature.

C. Nodal Agency & its Functions National Load Despatch Centre (NLDC) shall be the Nodal Agency for the implementation of the scheme under these regulations. The Nodal Agency shall perform the following functions: 

Act as Secretariat to the Monitoring Committee and the Appraisal Committee.



Prepare a Detailed Procedure for release and disbursement from PSDF consistent with the Procedure approved by the Monitoring Committee from time to time.



Keep the Record of Business transacted at each meeting of the Appraisal Committee and the Monitoring Committee.



Prepare detailed procedure for preparation of Budget, Accounting of receipts/ disbursals from PSDF Public Account and Audit with the approval of the Monitoring Committee.



Prepare Annual Report of the PSDF.



Perform such other functions as may be assigned by the Monitoring Committee and the Appraisal Committee.

PSDF shall be utilized for the following purposes: 





Transmission systems of strategic importance based on operational feedback by Load Despatch Centers for relieving congestion in inter-State transmission system (ISTS) and intra-State Transmission Systems which are incidental to the ISTS. Installation of shunt capacitors, series compensators and other reactive energy generates including reactive energy absorption and dynamic reactive support like static VaR compensator (SVC) and static synchronous compensator (STATCOM) for improvement voltage profile in the Grid. Installation of special protection schemes, pilot and demonstrative projects, standard protection schemes and for setting right the discrepancies identified in the protection audits on regional basis.

of

D. Appraisal Committee There shall be an Appraisal Committee headed by the Chairperson, Central Electricity Authority (CEA), to be constituted by the Government of India (Ministry of


Power) for scrutiny (techno-economic appraisal) and prioritization of the various projects proposals for funding from PSDF in line with Clause (4) of Regulation (4) of these Regulations and such other functions as may be assigned by the Monitoring Committee. To monitor the committee, Government of India (Ministry of Power) shall constitute an Inter-Ministerial Monitoring Committee under the Chairmanship of Secretary (Power) Government of India to be known as Monitoring Committee and shall also consist of representatives from the Ministry of Power, Ministry of New and Renewable Energy, Department of Expenditure (Ministry of Finance), Central Electricity Authority (CEA) and Planning Commission as Members. The Chief Executive Officer, Power System Operation Corporation Limited (POSOCO) shall be the Member-Secretary of the Committee. The Monitoring Committee will consider such projects (or their revised costs) for sanction based on the recommendation of the Appraisal Committee and communication of the Central Commission that such projects are in line with the principles defined in these regulations and have been prioritised in accordance with the principles envisaged in these regulations. Based on the sanctions by the Monitoring Committee, the funds will be released to the project entities from the Budget of Ministry of Power. This Committee will also supervise and monitor the implementation of various projects sanctioned by it. Release of funds from PSDF will be regulated as per the extant instructions of the Ministry of Finance in this regard. The release of funds to Nodal Agency from the Public Account for further disbursement to project entities will be made after exercising requisite expenditure control, provided that the scheme has adequate funds provisioned for in the Demand for 6.

IV. GRANT PROCEDURE OF MINISTRY OF POWER The grant procedure of MoP is as follows: a.

The Regional Power Committees, Generating Companies, Transmission Licensees, Distribution Licensees, Load Despatch Centers, Power Exchange as the case may be, shall furnish necessary details of the projects, schemes or activities to the Nodal Agency.

b.

The Nodal Agency shall place these projects or scheme or activities for techno-economic scrutiny by the Appraisal Committee.

c.

After scrutinizing the proposals, the Appraisal Committee shall submit its Appraisal Report and recommendations in writing to the Central Commission, and to the project entity who has submitted the proposal.

d.

The Nodal Agency will approach the Central Commission, along with the recommendations of the Appraisal Committee, for ascertaining that the projects/ scheme(s)/ activities are covered within the scope of these regulations.

e.

The Central Commission, on receipt of such reference, will look into the following aspects viz: 

Whether the proposed projects/ schemes/ activities are in line with the purposes defined in these regulations.



Whether the proposed scheme(s) have been prioritized in accordance with the principles envisaged in these regulations.

f.

If the conditions specified in clause (e) of this regulation are satisfied, the Central Commission shall communicate to the Nodal Agency that the proposed projects are in line with the principles defined in these regulations and have been prioritised in accordance with the principles envisaged in these regulations.

g.

The Central Commission, at this stage shall not go into the details of the project cost, which will be examined by the Appropriate Commission only at the time of filing of tariff petition by the project entity to ensure inter alia that the tariff in respect of such project / scheme is not claimed for the portion of grant from the PSDF.

h.

Based on the communication received in this regard from the Central Commission, the Nodal Agency shall approach the Monitoring Committee for sanction of the fund from the PSDF.

E. Assistance Pattern The funding will be made as a grant, subject to availability of funds. The quantum of grant shall depend on the strategic importance and the size of the project and shall be considered for release as per these regulations. Detailed guidelines in this regard shall be prepared by the Monitoring Committee. Execution, Operation & Maintenance of the Assets The project entity shall be responsible for the execution as well as Operation & Maintenance of the projects during its useful life. Operation and Maintenance of the Project/ scheme shall be governed in accordance with the Central Electricity Regulatory Commission (Terms and Conditions of Tariff) Regulations, 2014, as amended from time to time or any subsequent enactment thereof. Preparation of Budget, Accounts and other records Preparation of Budget, Accounting of Receipts/ disbursals from PSDF Public Account, Utilization Certificates, and Audit etc shall be governed in accordance with the provisions made in the Detailed Procedure in this regard. Implementation, Monitoring and Control of Projects/ Schemes (a) The Regional Power Committees, Transmission Licensees, Distribution Licensees, Load


Despatch Centers, Power Exchanges, Central Transmission Utility (CTU), State Transmission Utility (STU) for intra-State systems which are incidental to the ISTS will be the Implementing Agencies. (b) The Appraisal Committee in consultation with Ministry of Power will evolve a mechanism to evaluate the implementation of projects by laying down objective quantifiable financial and technical outcome parameters for each category of projects funded under the project / scheme. (c) The Monitoring Committee will supervise and monitor the implementation of projects on the basis of mechanism evolved but not limited to (b) above. Annual Report An Annual Report of the fund including the projects undertaken during the year, together with the Balance Sheet and Audited Accounts shall be submitted to the Central Government and for information to the Central Commission. The Annual Report shall also be laid on the table of both Houses of Parliament though the Ministry of Power. Power to remove difficulties If any difficulty arises in giving effect to the provisions of these regulations, the Commission may, by general or specific order, make such provisions not inconsistent with the provisions of the Act and the regulations made there under as may appear to be necessary for removing the difficulty in order to achieve the objectives of these regulations. Repeal and Savings (a) Save as otherwise provided in these regulations, Central Electricity Regulatory Commission (Power System Development Fund) Regulations 2010 are hereby repealed. (b) Notwithstanding such repeal, anything done or any action taken or purported to have been done or taken including any procedure, minutes, annual reports, confirmation or declaration or any instrument executed under the repealed regulations shall be deemed to have been done or taken under the relevant provisions of these regulations.

approved by the Government of India. The same is as per procedure laid down in Power System Development Fund fo the CERC Regulations, 2010, Power System Development Fund. With the operationalisation of PSDF by Government of India, its objective can be fulfilled to ensure that grid discipline is maintained under commercial mechanism. Those who breach the discipline are required to pay what is referred to as “Unscheduled Interchange charges”. This is payable when the users of the grid who should adhere to scheduled dispatch and drawal of electricity do not conform to their commitments. The four charges, namely Unscheduled Interchange Charge, Congestion Charge, Market Splitting Congestion Amount, and Reactive Compensation for failure to maintain voltage are settled between those who pay and those who need to receive. After final settlement takes place, there are surplus amounts which are credited into PSDF.

ACKNOWLEDGMENT The author acknowledged with thanks the contributions and support from Ministry of Power and Central Electricity Reguatory Commission in making this paper in presentable form. I also acknowledge the support from in house library of University of Petroleum and Energy Studies, Dehradun in collecting information in details on power system.

REFERENCES [1] [2] [3] [4] [5]

V. SUMMARY What we are seriously interested is in strengthening of country’s power system. The mere objective of the paper is to forward awareness about the above Scheme that is operationalization of the Power System Development Fund (PSDF) and utilization of funds deposited therein as

[6]

[7]

Lecture on power system available at http://www.nptel. iitm.ac.in /courses/108101005/ S.W. Blume, “Electric power systems Basics” for non electrical professionals, Wiley Interscience publication, 2007. “Electrical Grid” available at www.en.wikipedia.org/ wiki/ Electrical_grid “Power System Operation & Control” available PDF at elearning. vtu.ac.in/12/enotes/psoc/Unit1&6-BVS.pdf “Operationalisation of Power System Development Fund” Memo issued by Director inistry of Power, Govt of India, 10.01.2014 . Draft to lok Sabha Starred Question 321 to be answered on 13.2.2014, available at http://powermin.gov.in/loksabhatable/ pdf/ Lok_13022014_Eng.pdf CERC Notification on “Power System Development Fund” on 09.06.2014. available at www.cercind.gov.in

Concept and Design of Nano Hydro Generator Abhinav Kant Department of Electrical Engineering, National Institute of Technical Teachers and Research, Chandigarh, India e-mail: [email protected] Abstract—Small hydro power generation has huge potential when considered in the category of renewable energy. Fast flowing rivers constitute a substantial part of the untapped potential of hydro power. In order to become self energy sufficient a concept is being presented by this paper that can be implemented at the consumer level specially for rural villages and residences situated near rivers that carry water for the whole year. The design of a Nano hydro generator is described that can be installed at the river bed and produce sufficient energy to power a residential/commercial unit located near the river. The turbine design taken under study is Contra-Rotating SmallSized Axial Flow Hydro Turbine. Finally the conclusion is stated with speculations regarding the efficiency and practical feasibility of the device. Keywords: Nano-Generator; Hydro Power; Small Sized Axial Turbine; Contra-Rotating Rotor; Renewable Energy

I.

INTRODUCTION

There is a strong demand to change energy resources of fossil fuels into renewable energy such as hydropower, wind power, solar energy and so on. Small hydropower generation is alternative energy and the energy potential of small hydropower is large. Among various energy sources, mechanical energy is one of the most effort-attracting candidates because it universally exists in our living environment, but usually goes to waste. In this regard, nanogenerator (NG), for converting environmental mechanical energy into electricity, has been developed as a very effective and practically-applicable technology since 2006. The small hydropower is expected to low environmental destructions. Therefore, turbines which are suitable for specifications of low head in agricultural water and a small river are studied for their use in the proposed generator.

Fig. 1: Side Elevation

In this paper firstly the Autocad design of the generator is demonstrated and its working is explained. Then turbine designs are discussed that can used in the individual units of the generator.

II.

GENERATOR DESIGN

The generator will be installed at the river bed and will have an opening for the water from the surface to flow in through an adjustable inlet as shown in Fig. 1. A floater will keep the inlet steady on the surface of the river so that the fast flowing water from surface of the river can fall through the inlet onto the turbine matrix.

Fig. 2: Front Elevation

A cubical box with 4 turbines units arranged in form of a 2x2 matrix is used as the peculiar design.See Fig. 2 where the spaces have been presented for each turbine unit. This method gives the advantage of using the capability of four turbines for a particular flow rate.

Concept and Design of Nano Hydro Generator  41

water from the surface falls onto the turbine matrix. The inlet will also perform the function of streamlining the water flow so that we get a concentrated fast flow of water that will finally enter the turbine chamber. The inflow will be monitored by a water flow sensor that will constantly monitor the flow rate. The four turbine units will have separate flow tunnel that will bring in the water and rotate them. Each turbine unit will be monitored by a voltage sensor that will give us the value of the voltage being produced by each unit. This will help in maintenance and debugging any fault or malfunction. Further a power electronic circuitry will ensure constant production of an optimum voltage and form of current DC or AC as specified by the consumer.

IV. TURBINE DESIGNS

Fig. 3: Back Elevation

The back elevation in Fig. 3 shows the space for the power circuit and wire bundle which will transfer the power to the small power station or for direct usage whichever is feasible for the consumer.

The design taken for study focus on developing small sized efficient turbines. Contra-Rotating Small-Sized Axial Flow Hydro Turbine [3] is one such example that was developed in recent times. In the present paper, the performance and the internal flow conditions in detail of contra-rotating small-sized axial flow hydro turbine are shown with the numerical flow analysis.

A. Rotor Design Method and Design Parameters Test turbine was assumed to install in a pipe of agricultural water with diameter of about 2 inch and a small-scale water-supply system. The designed flow rate and head was Qd = 0.0102 m3/s and Hd = 4 m respectively based on the power (P = 100 W), head (H = 4 m), flow rate (Q = 0.01 m3/s) assumed in a pipe of agricultural water with diameter of about 2 inch and a small-scale water-supply system. The rotational speed of each front and rear rotor of the test turbine was Nf = Nr = 2600 min−1 in order to consider a characteristic of a small generator which can produce about 100 W. The rotor and the primary dimensions of a contra-rotating small-sized axial flow hydro turbine are shown in Fig. 5 and Table 1 respectively.

Fig. 4: Section Views

The other section views are shown in the Fig. 4. Various designs reflect the top and bottom faces of the energy box.

III. WORKING The water from the surface of the river will flow in through the opening and fall through the adjustable inlet. The height of the adjustable inlet will vary according to the level of the river water so that only the faster flowing

Fig. 5: Test Hydro Turbine Rotor

Casing diameter is 66 mm because tip clear-ance is 1 mm, and the hub tip ratio of the front and rear rotors were Dhf/Dtf = Dhr/Dtr = 32 mm/66 mm = 0.48. Each design


parameter was determined by power, head, flow rate, rotational speed. In this study, blade number of each front and rear rotor were set as a prime number; front rotor Zf = 4 and rear rotor Zr = 3 in order to sup-press the blade rows interaction of contra-rotating rotor. A guide vane was not set at the inlet of the front rotor because the test turbine was designed as compact as possible. The test turbine was designed so that swirling flows did not remain the downstream of the rear rotor at design flow rate. Further, a stagger angle of the rear rotor is determined on an assumption that the swirling flow the downstream of front rotor, which was calculated by the design efficiency of front rotor (ηfd = 65%), directly went to rear rotor. TABLE 1: PRIMARY DIMENSIONS OF TURBINE ROTOR Rotor Front Rear

Diameter (Mm) 32 Hub 48 Mid 64 Tip 32 Hub 48 Mid 64 Tip

Blade Number 4 3

Solidity 1.02 Hub 0.84 Mid 0.73Tip 0.72Hub 0.59Mid 0.52Tip

Stagger Angle 33.5Hub 27.4Mid 22.7Tip 53.1Hub 35.2Mid 26.4Tip

B. Numerical Analysis Method and Conditions In the numerical analysis, the commercial software ANSYS-CFX was used under the condition of 3D steady flow condition. Fluid was assumed that the incompressible and isothermal water and the equation of the mass flow conservation and Reynolds Averaged Navier-Stokes equation were solved by the finite volume method. The standard wall function was utilized near the wall and the standard k-ε model was used as the turbulence model. The inlet region was 5D upstream of the test section and the outlet region was 5D downstream of it. The constant velocity and the constant pressure were given as the boundary condition at the inlet and the outlet respectively. The numerical grids used for the numerical analysis were shown in Figure 6. The numerical domains were comprised of the inlet, rotor and the outlet regions. The numerical grid elements at each region were 59,137 for the inlet region and 61,568 for the outlet region respectively. The numerical grid elements for the rotor region were 2,962,437 and 2,350,803 for the front and the rear rotors respectively. The fine grids were arranged near the tip clearance and the blade. The y+ was 5 near the hub of the front and the rear rotor. The numerical analyses were performed at seven flow rate points of 90%, 100%, 120%, 140%, 160%, 180% and 200% of the designed flow rate. These flow rate points were mainly set to large flow rate points because the small hydro turbine could be operated in large flow rates.

Fig. 6: Numerical Grids. (a) Whole Regions; (b) Rotor Region

efficiency curves of each front and rear rotor obtained by the numerical analysis. The total pressure efficiency of the front rotor was calculated from the ratio of the shaft power of the front to the input which was obtained by the multiplication of the flow rate and the mass flow averaged total pressure difference between the section at the 2D upstream of the test section and the interface between the front and the rear rotors. The axial position of the interface was mid-section between the front and the rear rotors; the axial section 15.5 mm downstream from the trailing edge of the front rotor hub. Further, the total pressure efficiency of the rear rotor was also calculated from the ratio of the shaft power of the rear rotor to the input which was obtained by the flow rate and the mass flow averaged total pressure difference between the 2D downstream section of the test section and the interface between the front and the rear rotors.

C. Numerical Results Figure 7. shows the performance curves of the test turbine obtained by the numerical analysis. Fig. 8 shows total pressure

Fig. 7: Performance Curves

Concept and Design of Nano Hydro Generator  43

decreased at partial flow rate point 0.9Qd and large flow rate points 1.8Qd and 2.0Qd;

In Fig. 4, the total pressure efficiency of the front rotor was slightly affected by a flow rate change, however, the total pressure efficiency of the rear rotor drastically decreased in partial and large flow rates. Therefore, we investigated the internal flow at the large flow rate 1.8Qd in order to consider a cause of performance deterioration in the large flow rate range from the numerical results.

3.

Such hydro turbine design when combined with the generator design stated before that suggested a 2X2 matrix of such turbines could give us sufficient efficiency and output when operated under an appropriate monitoring and control system.

REFERENCES [1]

[2]

[3]

Fig. 8: Total Pressure Efficiency Curves of Front and Rear Rotor [4]

V. CONCLUSION Based upon the given study following conclusions can be obtained: 1.

2.

It was found that the maximum efficiency ηmax = 70.8 % was obtained, although the contrarotating small-sized axial flow hydro turbine was very small. Further-more, efficiency more than 50 % was obtained in relatively wide flow rates range of 0.9Qd-2.0Qd; Efficiency of the front rotor showed comparatively high values in 0.9Qd-2.0Qd. However, efficiency of the rear rotor drastically

[5]

[6]

[7]

[8]

A. Furukawa, K. Okuma and A. Tagaki, “Basic Study of Low Head Water Power Utilization by Using Darrieus-Type Turbine,” Transactions on JSME, Vol. 64, No. 624, pp. 2534-2540. (in Japanese) 1998. T. Kanemoto, A. Inagaki, H. Misumi and H. Kinoshita, “Development of Gyro-Type Hydraulic Turbine Suitable for Shallow Stream (1st Report, Rotor Works and Hy-droelectric Power Generation),” Transactions on JSME, Vol. 70, No. 690,, pp. 413-418. (in Japanese) 2004. Ryosuke Sonohata, Junichiro Fukutomi, Toru Shigemitsu 1Graduate School of Advanced Technology and Science, The University of Tokushima, Tokushima, Japan 2Institute of Technology and Science, The University of Tokushima, Tokushima, Japan Email: [email protected] Received September 24, 2012; revised November 6, 2012; accepted November 15, 2012. J. Matsui, ‘‘Internal Flow and Performance of the Spiral Water Turbine,’’ Turbomachinery, Vol. 38, No. 6, pp. 358-364. (in Japanese) 2010. T. Ikeda, S. Iio and K. Tatsuno, “Performance of Nano-Hydraulic Turbine Utilizing Waterfalls,” Renewable Energy, Vol. 35, No. 1, pp. 293-300. 2010. M. Nakajima, S. Iio and T. Ikeda, “Performance of Savonius Rotor for Environmentally Friendly Hydraulic Turbine,” Journal of Fluid Science and Technology, Vol. 3, No. 3, pp. 420-429, 2008. S. Iio, F. Uchiyama, C. Sonoda and T. Ikeda, “Performance Improvement of Savonius Hydraulic Turbine by Using a Shield Plate,” Turbomachinery, Vol. 37, No. 12,, pp. 743-748. (in Japanese) 2009. S. Iio, S. Oike, E. Sato and T. Ikeda, “Failure Events in the Field Test of Environmentally Friendly Nano Hydraulic Turbines,” Turbomachinery, Vol. 39, No. 3, pp. 162-168. (in Japanese), 2011.

Selection of a Custom Power Device for Power Quality Improvement Under Non-sinusoidal Conditions Tejinder Singh Saggu

Lakhwinder Singh

Assistant Professor, Electrical Engineering, PEC University of Technology Chandigarh & Research Scholar, PTU, Jalandhar, India e-mail: [email protected]

Professor, Electrical Engineering, Baba Banda Singh Bahadur Engg. College, Fatehgarh Sahib, India e-mail: [email protected]

Abstract—Control of ac power using thyristors and other semiconductor switches is widely used to provide controlled electric power to various non-linear loads. This increased use of power electronic based loads is the main concern for harmonic distortion in the ac supply system. Unfortunately there are some problems associated with these new power electronic circuits and devices. Unlike conventional loads they control the flow of power by modifying the sinusoidal power system voltages and currents either by flattening or chopping them. To increase the reliability of the distribution system and face the power disturbance problems, an advanced power electronics controller devices have launched over last decades. The evolution of power electronics controller devices has given to the birth of custom power. In this paper, an attempt has been made to discuss various custom power devices and the type of application in which they can be used for the improvement of power quality. Keywords: Power Quality, Harmonics, Voltage Variations, THD, D-STATCOM, SVC, DVR, UPQC

I.

INTRODUCTION

The power quality concept is exceedingly imperious to industrial and commercial designs of power system. The non-linear loads are increasing day by day especially in case of electronic devices for the power system control [1]. For the both consumers and the utility which supplies them, the power quality issues are different. Nonlinear loads give rise to troubles and serious problems to their utility as well as to the customer equipment. Bursting of capacitors, blown fuses, insulation failure and overheating of power equipment such as transformers, cables and motors are the common effects of harmonic distortion, especially voltage distortion. One possible solution is to place uninterruptible power supplies (UPS) between critical loads and the power system. However, UPS systems are quite expensive, and while they do a good job in protecting their own load, they are also the major power system polluters and often cause problems for neighboring loads. Thus, there exists the need to modify or design new and innovative circuits that can be placed at the user end to reduce distortion level or to cancel the effect of transient phenomena, and provide back up for end users which we get now through UPS systems. One innovative concept is

the Active Power line conditioner (APLC) also known as AF’s. It appears to be an attractive and feasible method for reducing voltage and current harmonic distortion, flickers, voltage spikes and transients. It injects equal but opposite harmonic thereby cancelling the original problem and improving power quality of the system.. If a facility has more than 15 % non-linear load, then a harmonic study should be performed before applying the power quality solutions. Even the most advanced transmission and distribution systems are not able to provide power with the desired level of reliability for the proper functioning of the loads in modern society [2].

II.

MAIN CAUSES OF POWER QUALITY DEGRADATION

The degradation of power quality could be due to either of the following:

A. Different Voltage Variations It has been found that widely held power quality problems are related to issues within a facility as opposed to the utility as about 80–90 % of power quality problems are caused within the site. The main problems include grounding and bonding issues and power disturbances due to internal disturbances typically when we connect different equipment from the same power source. The other factors responsible for power quality degradation are due to sudden increase in voltage which is known as voltage swell and sudden decrease in voltage which is known as voltage sag or voltage dip. Generally in case of power systems, every increase in current causes a consequent decline in voltage. But these reductions are small enough that the voltage remains within normal acceptable limits. But when there is a large increase in current, or when the system impedance is high, the voltage can drop significantly. So voltage sag is either due to steep increase in current or due to increase in impedance of system. The main reasons for voltage sags are due to abrupt increases in loads such as short circuits or faults, motors starting, or electric heaters turning on, or they are caused

Selection of a Custom Power Device for Power Quality Improvement under Non-sinusoidal Conditions  45

by abrupt increases in source impedance typically caused by a loose connection. The voltage swells are almost always caused by an abrupt reduction in load on a circuit with a poor or damaged voltage regulator, although they can also be caused by a damaged or loose neutral connection [3]. The voltage swells are commonly caused by system fault conditions, switching off a large load or energizing a large capacitor bank. A swell can also occur during a single line-to-ground fault (SLGF) with a temporary voltage rise on the un-faulted phases. They are not as common as voltage sags and are characterized also by both the magnitude and duration. During a fault condition, the severity of a voltage swell is very much dependent on the system impedance, location of the fault and grounding. The effect of this type of disturbance would be hardware failure in the equipment due to overheating. When there are reductions in the voltage or current supply, interruptions take place. Interruptions may occur due to various reasons, some of them being faults in the power system, failures in the equipment, etc. The entire three phenomenons have been shown in Fig. 1.

TABLE 1: EFFECT OF THD ON VOLTAGE DISTORTION LIMIT Bus Voltage at Power Control Centre Less than 69 kV 69–161 kV More than 161 kV

Individual Voltage Distortion (%) 3 1.5 1

THD (%) 5 2.5 1.5

Thus it has been clearly shown that, as the level of voltage increases, THD value decreases. The best solution to this is to optimize the PF and THD. Thus, THD can be restricted within the specified limits while optimizing the power factor [6].

III. DIFFERENT TYPES OF ACTIVE FILTER CONFIGURATIONS There are two different fundamental approaches for improving power quality with active filters firstly due to correction in time domain and secondly by correction in frequency domain configurations. Either of these can be used in conjunction with Current Source Inverters (CSI) and Voltage Source Inverters (VSI). The three different time domain correction approaches are:

A. Triangular Wave This method is the easiest to implement it can be used to generate either a two state or three state switching functions. A two state switching function consist of dc source that can be connected either to positive or negative output. A three state switching function can be +ve,-ve or zero. Therefore the inverter is always on when two state switching functions is used but it can be off when three state switching function is used.

B. Hysteresis Fig. 1: Different Voltage Variations

B. Effect of Harmonics Harmonics obstruct with the sensitive electronic equipment and networks. Various standards by IEEE and IEC have been adopted for the harmonic reduction techniques based upon the certain international standards. The harmonic measurement is generally expressed by THD (Total harmonic distortion) which is one measure of the total distortion on waveform. It is defined as the root mean square (RMS) value sum of the harmonics, shared by one of two values either the fundamental or the RMS value of the total waveform. It can also conclude that power quality has direct impact on the power factor. Due to the presence of harmonics, the neutral conductors may overheat and transformers and motors become less efficient [4]. For the indication of harmonic severity and its waveform content, there are several definite measures used in practice [5]. The consequence of THD on voltage distortion has been shown in the Table 1.

This is the most commonly proposed time domain correction technique. The preset upper and lower tolerance limits are compared with the extracted error signal. As long as the error is within the tolerance band, no switching action is done. Switching action occurs whenever the error leaves the tolerance band.

C. Deadbeat The control based switching functions have been proposed for inverter switching circuit but not yet been used with APLC’s. On the other hand, the correction in frequency domain is based on the principle of periodicity and fourier analysis of the distorted voltage or current waveforms to be corrected. For situation where there are few predominant and fixed harmonic present, more recent references use fourier transform to determine the harmonics to be injected. Once the Fourier transform is done, an inverter switching function is computed to produce the distortion canceling the output. This can be accomplished with either two states or three state switching functions. The inverter


switching frequency must be more than twice the highest compensating harmonic frequency. The difference between the two approaches is as shown in Table 2. TABLE 2: COMPARISON OF TIME & FREQUENCY DOMAIN CORRECTION APPROACHES S. No. Time Domain 1 Fast response to changes in the power system. 2 Time correction techniques take measurement at only one point in the power system. 3 They are not well suited for overall network connection 4

3.Easy to implement & has little computational burden

Frequency Domain Slow response as compared to time domain. Frequency domain correction can handle single node generally problem. They can be extended to minimize harmonic distortion through the network. Increased computational burden.

IV. DIFFERENT CUSTOM POWER DEVICES FOR POWER QUALITY IMPROVEMENT

controlling the firing angle of the thyristors, while each capacitor can only be switched on and off at the instants corresponding to the current zero crossings, in order to avoid inrush currents in the capacitors. Having that type of construction arrangement, the SVC is able to generate continuously variable reactive power in a specified range, and the size of the TCR is limited to the rating of one TSC branch. The size of the reactor limits the power that can be absorbed in the inductive range. The SVC can be found in applications such as power line compensation, compensation of railway feeding system, reducing disturbance from rolling mills and arc furnace compensation (both for reactive power supply and for flicker mitigation). The ability to absorb changes in reactive power makes to some extent the SVC suitable for flicker reduction. However, the ability of the SVC to mitigate flicker is limited by its low speed of response.

A. D-STATCOM

Fig. 2: D-STATCOM

A distribution system suffers from current as well as voltage-related power-quality (PQ) problems, which include poor power factor, distorted source current, and voltage disturbances [7] [8]. D-STATCOM injects a current into the system to correct the different voltage variations as discussed before. It provides quite good voltage regulation. The Pulse Width Modulation (PWM) based control only measures the r.m.s voltage at the load point and no reactive power measurements are being made. A simple configuration of DSTATCOM is shown in Fig. 2.

B. Static VAR Compensator An SVC is typically used for ac voltage control by generation and absorption of reactive power using passive elements. It can be used for balancing unsymmetrical loads also. It is constituted by one thyristor controllable reactor (TCR) and a number of thyristor switched capacitor (TSC) branches as shown in Fig. 3. The value of the reactance of the inductor is changed continuously by

Fig. 3: SVC

C. Dynamic Voltage Restorer Dynamic Voltage Restorer (DVR) is the most efficient and effective modern custom power device used in power distribution networks. The DVR is essentially a voltage-source converter connected in series with the ac network via an interfacing transformer, which was originally conceived to a ameliorate voltage sags [9]. DVR is a recently proposed series connected solid state device that injects voltage into the system in order to regulate the load side voltage. It is normally installed in a distribution system between the supply and the critical load feeder at the point of common coupling (PCC). Other than voltage sags and swells compensation, DVR can be also are added to other features like: line voltage harmonics compensation, reduction of transients in voltage and fault current limitations. On event of fault which results in voltage sag, the magnitude reduction is accompanied by phase angle shift and the remaining voltage magnitude with respective phase angle shift is provided by the DVR.

Selection of a Custom Power Device for Power Quality Improvement under Non-sinusoidal Conditions  47

Employing minimum active voltage injection mode in the DVR with some phase angle shift in the post fault voltage can result in miraculous use of DVR. If active voltage is less prominent in DVR then it can be delivered to the load for maintaining stability. The main components of DVR are energy storage unit, voltage source inverter circuit, and filter unit and series injection transformers as shown in Fig. 4. DVR can operate in three modes naming Protection mode, Standby mode or Injection mode.

achieving required performance from a UPQC system by maintaining the dc bus voltage at a set reference value. UPQC is mainly used to compensate for various power quality issues like voltage sags, swells, unbalance, flicker, harmonics, and for load current power quality problems [11][12].

Fig. 5: UPQC Fig. 4: Dynamic Voltage Restorer

The overall comparison of all the three devices is shown in Table 3. It has been shown that DVR is superior to other two devices due to number of factors as mentioned in Table 3. TABLE 3: COMPARISON OF VARIOUS CUSTOM POWER DEVICES S. No. Factors 1 Rating 2 Speed of operation 3 Compensatio n Method 4 Active /reactive Power 5 Harmonics 6 Problems addressed

SVC

Shunt Compensation Reactive

DSTATCOM low More than SVC Shunt Compensation Reactive

high Transient

Less than SVC Sag/Swell

low low

DVR high Fast Series Compensation Active/ Reactive Very less Sag/Swell/ Harmonics

D. UPQC As the active filters configuration is of mainly two types; one is series based & other is shunt based. The former configuration is used to handle voltage based problems and the latter is used to handle current based. For a better supply system, both voltage supplied and current drawn in a system needs utmost importance. However, installing these two separate devices independently to compensate voltage and current related power quality problems may not be a cost effective solution. Unified Power Quality Conditioner is a combination of both series and shunt active power filters having a common dc bus. The shunt inverter in UPQC is controlled in current control mode such that it delivers a current which is equal to the set value of the reference current as governed by the UPQC control algorithm. Additionally, the shunt inverter plays an important role in

The construction of UPQC is quite similar to a unified power flow controller (UPFC). Both these devices use two voltage source inverters (VSIs) that are connected to a common dc energy storage element. The main difference lies in their field of application as UPQC is used in distribution network and UPFC is used in transmission network to perform the series and shunt compensation concurrently. However, a UPFC only needs to provide balance shunt and/ or series compensation, since a power transmission system generally operates under a balanced and distortion free environment. On the other hand, a power distribution system may contain dc components, distortion, and unbalance both in voltages and currents. Therefore, a UPQC should operate under this environment while performing shunt and/ or series compensation.

V. CONCLUSION In this paper, an overview of the custom power devices for improving power quality has been presented. The main reasons for power quality degradation have been discussed and then different correction approaches of active filters have been shown. Advantages and drawbacks of several custom power devices have been pointed out. Then a comparison has been done on the various devices in which it has been found that DVR has superior properties than STATCOM & SVC. The performance of UPQC has also been discussed if we need improvement in both series and shunt based configurations simultaneously. Also it has been shown that custom power devices provide in many cases higher performance compared with traditional mitigation methods. However, the choice of the most suitable solution depends ultimately on the characteristics of the supply at the point of connection, the requirements of the load and economics.


REFERENCES [1]

[2]

[3] [4] [5]

[6]

Zamora I, Mazon A, Eguia P, Albizu I, Sagastabeitia K.J, Fernandez E, "Simulation by MATLAB/Simulink of active filters for reducing THD created by industrial systems," IEEE Power Tech Conference Proceedings 2003, Bologna, vol. 3, pp. 8, 23-26 June 2003. A de Almeida et al. “Power Quality Problems and New Solutions”, ISR, Department of Electrical and Computer Engineering, University of Coimbra, Portugal. Power Quality standards, “Computer Power & Consulting Corporation”, 8225 North 46th Street, Omaha, NE 68152. Power Standards laboratory, “A measure of power quality”, Tutorials & Standards. Singh Tejinder, Arvind Dhingra “Various Concerns Regarding Monitoring & Measurement of Power Quality Problems”, International Conference of Young Scientists on Electric Power Engineering & Control systems 2011 at LVIV, Ukraine, Nov 24-26, 2011. George S, Agarwal V, "Optimum Control of Selective and Total Harmonic Distortion in current and voltage under non-sinusoidal conditions”, IEEE Transactions on Power Delivery, vol. 23, no. 2, pp. 937-944, April 2008.

[7]

H. Fujita and H. Akagi, “Voltage-regulation performance of a shunt active filter intended for installation on a power distribution system,” IEEE Trans. Power Electron., vol. 22, no. 3, pp. 1046–1053, May 2007. [8] C. Kumar, S. Member, M. K. Mishra, and S. Member, “A VoltageControlled DSTATCOM for Power-Quality Improvement,” vol. 29, no. 3, pp. 1499–1507, 2014. [9] P. Roncero-sánchez, E. Acha, S. Member, J. E. Ortega-calderon, and V. Feliu, “A Versatile Control Scheme for a Dynamic Voltage Restorer for Power-Quality Improvement,” vol. 24, no. 1, pp. 277–284, 2009. [10] V. Khadkikar, “Enhancing Electric Power Quality Using UPQC :,” vol. 27, no. 5, pp. 2284–2297, 2012. [11] A. Sannino, J. Svensson, and T. Larsson, “Power-electronic solutions to power quality problems,” Electr. Power Syst. Res., Vol. 66, no. 1, pp. 71–82, Jul. 2003.

Design and Analysis of Grid-tied PV System Without Batteries: In Context to India Ranjay Kumar Ojha M.E.III Semester, I&C (EE) Department, NITTTR, Chandigarh, India

e-mail: [email protected] Jayachandra Dama

Lini Mathew

M.E. III Semester, I&C (EE) Department, NITTTR, Chandigarh, India e-mail: [email protected]

Associate Professor, Electrical Engineering Department, NITTTR, Chandigarh, India e-mail: [email protected]

Abstract—In India, the role of Distributed Generation (DG) is increasingly being acted as a substitute and it is large alternative of conventional electric power supply. The government and other energy awareness organizations have tried to promote solar home system in off-grid region. Even though centralized economic system that solely depends on cities is hampered due to energy problems, the use of solar power never been tried in cities in large scale due to technical inconvenience, high installation cost and high maintenance cost of battery bank. To overcome these problems, this paper proposes an optimized design of grid-tied PV system without battery which is suitable for India. This system requires less installation cost, less maintenance cost and this system capable to supply a load when the grid power fails. This paper also analyzes the implementation outcome of integrating this grid-tied PV system in grid connected areas, especially in the capital of India. Keywords: PV System without Storage, Grid-tie Inverter, Critical AC Load, Transfer Switch, Control Scheme, Anti-Islanding

I.

INTRODUCTION

Due to increasing cost and depleting storage of conventional sources of energy and the increasing concerns for global climate change, use of Non Conventional sources of Energy (NCE) has become indispensable for any country in the world. In case of India where declining resources and power crisis hinder the economic vision and industrial development inflexibly, it is even more encouraging to maximize the use of NCE. At present, India depends mostly on Conventional sources of Energy (CE) particularly coal resources for its power generation and its 60–70 billion tons of present proven coal reserve would be exhausted by 2040–44 if the demand continuous to increase at present rate [1]. National demand in 2009–10 of electricity was 8,30,594MW with shortage of around 83,950MW (10.1 %) for low economical growth [2]. According to central electricity authority of India (CEA) in June 2013 the demand for electricity is 1,28,612MW and supply is 1,22,883MW with a supply gap of 4.5 % but in the month of May 2013 gap is 6.3 % [3]. India mainly depends on coal based thermal power plant, but high grade coal is not available and percentage increase in coal production is very low so

we cannot generate sufficient power from coal based thermal power plant. With conventional resources which by now started to shrink, it is not possible to even get closer to attain the target. It is evident why India's Ministry of New and Renewable Energy has released the Jawaharlal Nehru National Solar Mission (also known as the National Solar Mission (JNNSM) Phase 2 Draft Policy by which the Government aims to install 10GW of Solar Power and of this 10GW target, 4GW would fall under the central scheme and the remaining 6GW under various State specific schemes [4]. In July 2009, India unveiled a US$19 billion plan to produce 20GW of solar power by 2020 [5]. Under the plan, the use of solar-powered equipment and applications would be made compulsory in all government buildings, as well as hospitals and hotels [6]. On 18 November 2009, it was reported that India was ready to launch its National solar mission under the National Action Plan on Climate Change, with plans to generate 1,000MW of power by 2013 [7]. From August 2011 to July 2012, India went from 2.5MW of grid connected photovoltaic to over 1,000MW. With about 300 clear, sunny days in a year, India's theoretical solar power reception on only its land area is about 5000 Peta Watthours per year (PWh/yr) (i.e. 5,000 trillion kWh/yr or about 600,000GW) [8-10]. The daily average solar energy incident over India varies from 4 to 7 kWh/m2 with about 1,500–2,000 sunshine hours per year (depending upon location), which is far more than current total energy consumption. For example assuming the efficiency of PV modules were as low as 10 %, this would still be a thousand times greater than the domestic electricity demand projected for 2015 [11]. In this scenario, already, the village community of India adopted the simplest but yet most effective one, the off-grid home PV systems. On the contrary, city dwellers are not sufficiently interested to utilize Solar Home Systems (SHSs) largely due to technical inconvenience, high installation cost and absence of policy enforcement. This paper demonstrates a technically optimized low cost grid-tied PV system in point of view of India and how it can be a benefit for the city dwellers to limit the monthly cost and also contribute to the grid.

50 International Conference on Recent Advances and Trends in Electrical Engineering (RATEE-2014)

II.

OFF-GRID VS. GRID-TIED PV SYSTEM

energy to the grid when the grid power is available and backup the on-site critical load when the grid power is unavailable and sunlight is available.

Fig. 2: Schematic of Grid-tied PV System

Fig. 1: Schematic of an OFF-grid PV System with DC Loads

Currently in India, most of the PV systems are installed in rural areas which have very little chance of getting connected to the national grid within 5-10 years. Due to this reason; off-grid SHSs are the most popular renewable energy application which has maximum growth rate for many years in India. Over the span of three years more than 16,000 solar home systems have been financed through 2,000 bank branches particularly in rural areas of south India where the grid does not yet extend. The total installed capacity of renewable source in India is 973.13MW out of which off grid solar system has capacity of 159.77MW [12] Typical configuration of a rural off-grid PV system in India is shown in Fig. 1. To achieve the aim of having 20GW energy from solar sources, we need to grab every opportunity of increasing up. If we closely track the technology trend of developed countries in this regard, we can find 90% of the European PV systems are Gridconnected [13]. Following the world trend of grid-tied PV market, cities like Delhi, Chandigarh, and Mumbai etc. have high potential to use the solar energy through gridtied PV systems. Configuration of a typical grid-tied PV system is given in Fig. 2.

III. PROPOSED GRID-TIED PV SYSTEM A grid-tied PV system without storage has been suggested to give power on-site electrical loads; serve

A. Configuration The system consists of PV arrays, a step-up dc–dc converter, a grid-tie inverter (GTI), controller (microcontroller) and an automatic AC transfer switch. PV arrays change solar energy into electric energy. The output voltage level of PV arrays is very low so we use a step-up dc–dc converter that boosts the array voltage to a higher level. The GTI inverts the DC power produced by the PV array into AC power with the desired voltage and power quality as required by utility grid. The controller sends a signal to transfer switch which changes supply source and also chooses serving loads according to available power. In standard condition, the system will feed energy to the grid; if the PV array output and grid power both are available and grid power. To sell energy back to Distribution Company we can utilize net metering facility. But when the utility grid power is not available or when the synchronization is not possible due to lower voltage level or lower frequency level, the system automatically disconnects the grid by using an anti-islanding system. In this circumstance, existing battery less grid-tied PV systems do not provide to any loads. But in our considered design, when sun light is available, it will supply some loads during the grid failure. This feature is indispensible considering the grid load shedding condition in India especially in summer season when power requirement is very high.

Design and Analysis of Grid-tied PV System Without Batteries: In Context to India 51

PV Array

DC/DC Converter

L2 Q2

L1

DC/AC Inverter

Q3

D1

TX1

D2

D3 C3

DC

Transformer switch

C1

Q1

C2

INPUT

Q4

Q5 D4

Grid

Controller

D5

Comparator

Critical AC load Fig. 3: Configuration of Proposed Grid-tied System

Q6

Q7 L3

B. Grid-tie Inverter The basic element of Grid-tied PV system is the GTI which regulates the voltage and current which comes from solar panels and also ensures that power supply is in phase with the available grid power. On AC side, it keeps the sinusoidal output synchronized to the grid frequency (nominally 50Hz in India). The voltage of the inverter output should be variable and it needs to be higher than the grid voltage to supply the current to the utility grid [14]. Fig 4 shows the schematic of a grid-tied inverter. The operating principle of a grid-tied inverter with three power stages has been illustrated. In first stage, the DC input voltage is stepped up by the boost converter and a combination of inductor L1, MOSFET Q1, diode D1 and capacitor C2. The inverter offers a galvanic isolation between input and the output. We can use a step-up transformer TX1, instead of the first stage (boost converter). In this case, to provide isolation in the second stage, a high frequency transformer is used. This stage is basically a pulse-width modulator DC-DC converter. The output voltage must be higher than the peak of the utility grid AC voltage. For example, 230 V, AC service voltage, requires the DC link greater than 230*√2= 325V. In the third conversion stage, DC is changed into AC by using a full bridge converter, which consists of IGBT Q6-Q9 and LC-filter L3, C4. Output LCfilter reduces harmonics to produce a sine-wave voltage. Typical modern GTIs have a constant unity power factor which means its output voltage and current are completely lined up and its phase angle is within 1 degree of the AC power grid. The GTI has an on board computer which will sense the current waveform of grid and provides an output voltage to correspond with the grid. In addition, when the grid is down, the GTI will provide AC output synchronized with pre-defined references.

Q8

Q9

C4

AC OUTPUT

Fig. 4: Schematic of a Grid-tied Inverter

C. Control Scheme Fig. 5 illustrates the scheme of control for proposed system. It consists of three parts

1) PV converter control PV arrays, a step-up dc–dc converter, a grid-tie inverter (GTI) and an automatic AC transfer switch with a controller (microcontroller). The output power of a PV array depends on the voltage level where it operates under a given condition of cell-surface temperature and irradiance. For better efficiency, a PV array should operate almost at the peak point of the V −P curve. A variety of Maximum Power Point Tracking (MPPT) techniques have been discussed in [15] and [16]. The MPPT block senses the PV array current IPV and array voltage VPV and returns the array voltage command. The PV converter controls the array voltage VPV at the reference voltage V*PV commanded by the MPPT controller and boosts the voltage to the level of desired dc voltage. Error between the ordered and real voltage is processed through the voltage controller into the ordered current I*PV, which is compared with the array current IPV.


this small push-and-pull has no effect. However, if the inverter is the only source supporting an islanding grid, it will rapidly push the voltage and frequency outside the inverter’s acceptable window of operation, triggering the inverter to shut down. But the problem is that in India power crisis is severe. Hence, the grid shuts down its feeders many a time during a day and existing battery less inverter remains OFF even though power is available in PV array until the grid would come back and it would run again. In our design we used an automatic transfer switch with a control circuit. When power will not available in grid, the control circuit will send a command to transfer switch and transfer switch will be activated in inverter only mode. In this mode, the inverter will reactivate the output transistors to continue supplying power to loads wired into the critical load panel which is separately connected from the grid. In this way, when the grid goes down and the inverter is sending power only to the critical load panel, PV power is not allowed energizing from the utility lines. Fig. 6 presents the complete flow chart of our planned control scheme.Fig.6. Fig. 5: Schematic Control for Grid-tied PV System

START

2) GTI control Basic concept of GTI control is to obtain the maximum power from varying sun irradiation and minimize the rating of the inverter by regulating reactive power generation. Below a specific solar irradiation, real power from the PV system is controlled to obtain the maximum power from changeable sun irradiation to supply either on-site electrical loads, or to supply power to the grid when the PV system output and sufficient sun light are available. But, when the grid fails for load shedding, or voltage level and frequency level goes down beyond usual limits the inverter stops output initially for few seconds, and then the transfer switch moves to inverter only mode and finally the inverter starts to give output to the critical on-site loads(approximately 30 % of installed capacity of solar plant) with own pre-defined references until the grid is come back.

3) Anti-islanding control

Measure voltage and frequency of grid

Is grid power available?

NO

No

Move switch to inverter grid mode

Synchronisation with grid

Is PV array power available?

YES LESS THAN 30%

YES

Compare power with 30% of installed capacity

Is synchronisatio n completed?

YES

NO

Operate anti -islanding GREATER THAN 30%

Move switch to Uif! dpoejujpo! xifsf! b! HUJ! dpoujovft! up! inverter only mode tvqqmz! qpxfs! up! uif! hsje! jo! uif! evsbujpo! pg! cmbdlpvu! jt! dbmmfe! jtmboejoh/ Due to the technical Inverter synchronization requirements as mention in IEEE 1547, to avoid the with reference condition, inverter will detect the voltage and frequency of Fig. 6: Flow Chart of Control Scheme the grid. If voltage and frequency are less than set values, the inverter will switch OFF. In addition a new complicated active detection scheme is necessary to D. Advantages of Proposed Scheme decrease the non-detection zone. So the inverter will use a • If the grid power is not available and sun light is variety of methods to efficiently push and pull a little on available, still the system will continue to supply the grid voltage and frequency. When the grid is available,

Design and d Analysis of Grrid-tied PV Syste em Without Battteries: In Context to India 53 3

loads (approximaately 30 % of installed peak watts of solar plannt). •

m would requuire a battery bank Usuaal solar system for storing s electriccal energy. Thhis requires a huge investment for thee house ownerr before they could c buildd a functionaal substitute energy e system m. By remooving the needd for an expensive battery bank and replacing thhe larger, exxpensive gridd-tied inverrters with smaaller, cheaper units that havve not needd of batteries, it brings the implementatioon of a sollar grid-tied hoome system, which w is withiin the finanncials take holld for more peeople.

•

Mosstly energy efficient system usees a convventional systeem which conntains a batterry for electtricity storagee. It ensures full use of solar energy however battery b dischaarge rate is 600% in I usuaal off-grid solaar systems in India.

•

As batteries deegrade with time and need a it requirees an replaacement, propper disposal and extraa care and maintenance. m The utilizatioon of batteery system is not normallyy taken as posssible subsstitute since thhe disposal of batteries mayy also source of some othher environmeental impact.

•

Gridd-tied inverterss are flexible that allows syystem to addd more solarr panels or wiind turbines. If I we use grid –tie inveerter in paralllel it allows more power handling caapacity.

will be producedd per day forr a 5kW batttery less PV V systeem. Besides we have collected the daata of energyy consumption in reecent years forr some typicaal house. Thenn we have h averagedd those data, ccorrelated them m with typicall weatther conditionns and finally estimated a nominal n housee energ gy demand foor each day inn Delhi city. Fig. 7 showss comp parison of daily d energyy demand an nd estimatedd geneeration from a 5kW PV systtem for a typiical householdd in Delhi. It is conncluded from Fig.7 that a household h cann save major partt of their eelectricity billl and enjoyy unintterrupted pow wer supply by installing a hiigh-rated grid-tied PV system without batteery. In generral if we cann enco ourage and im mplement this installation in n major citiess of In ndia, it can also a contributte in great amount a to thee natio onal energy prrofile.

IV. PROSPECT R ANA ALYSIS FOR DELHI CITY Here we w investiggate the opportunity and implementatioon outcomes of o our propossed system in point of view of Delhi, D the cappital of India and centre of o all political activvities. Delhi has h the potentiial to build arround 2.6GW of soolar PV on its rooftops. The Governnment buildings havve a solar potential 339 MW W. With overr 300 days of uninnterrupted sunnshine Delhi is ideal placce to harvest solar energy. Acccording to Roooftop Revoluution: D Solar Potential a report r releaseed by Unleashing Delhi’s green peace last year outt of 700 squaare kilo meteers of Delhi’s total build up rooof space about 31 squaree kilo meters can bee used to geneerate 2,557MW W electricity [17]. Whereas the load l of Delhi is 2529MW as a on today i.ee. 16th Nov, 2014 [18]. An orrdinary housee in Delhi, may consume arouund 10–15 kW Wh/day. A 5kkW Solar Gridd-tied system for a home has coost around Rs 5–7 lakhs could c meet 30 % of house dem mand. As syystem life tim me is assumed to have 25 years, part of the innitial capital cost is highly possibble to recover. And if we increase i DC rating r of our considdered PV systtem, the resullt gap between the on-site demannd and on-sitee generation can get even clloser. Delhi is situuated in 28.388N degrees north n latitudee and 77.12 E degrrees east longgitude. From the t solar radiiation pattern surveyyed in Delhi and a with the help h of solar ennergy calculator [199].We have esstimated the average a powerr that

Fig. 7: Hourly Estiimated Generatioon vs. House Dem mand of Delhi

V. LIMIITATION AND D SCOPE OF WORK Proposed P griid-tied system without storage can'tt supp ply electricity if utility grid is not avaailable duringg nightt or on rainyy day when suunlight is nott sufficient too geneerate power. Innstallation of a small batterry could solvee the problem p but thhe installationn cost and maiintenance costt woulld be higher and it wouldd be less effficient. Powerr outpu ut from certaain renewable energy sourcces, like windd and solar, can be irregular. F Fluctuations in i output aree harm mful for pow wer grid frrequencies, voltages v andd comp ponent perforrmance, causinng instability in the powerr geneeration system m and healthhy service to t customers. Conccerns about poower system reliability lim mit the amountt of new n and reneewable energyy that powerr utilities andd transsmission systeem operators aallow to be connected to thee grid. In future we will go forr simulation and hardwaree implementation off our system and tune it to o provide gridd qualiity AC supplyy limiting harm monics, DC in njection etc.


Moreover, our utilities should step forward to upgrade the existing girds in India in order to get full advantage of grid-tied incentive tariff will promote and encourage PV grid-tied solar system.

[4]

[5]

VI. CONCLUSION The global solar industry developed at a rate of 30 to 40 percent per year from 1999 to 2005, but after 2005 it has slowed to 19 percent due to silicon shortage [20–21]. There is a fair chance, in near future; price of the mostly used raw material silicon for PV array will hike. As India's solar industry which is almost only dependent on export will face a major crisis. Immediate measurement needs to be taken before that situation. Although India in its existing grid system doesn’t quite support effective tie with distributed generation for the time being, integration of grid-tie system with existing system need not total altercation of the system. Initiative to utilize the solar energy through latest technologies, in perspective of India, like Grid-tied solar system to complement existing energy system wants to be taken. Although India is still in initial stage to tackle all these issues related to distributed generation, an incentive tariff has been proposed for electricity generated from renewable sources. So absolutely there will be occurring lots of activity regarding grid-tied PV system for India in near future and we hope our work will help to make a decision of optimized way. So, in this paper we have proposed an optimized system which is more suitable for India to show how the grid-tied PV systems can be deployed with the idiosyncrasies of this country. We proposed the control structure of converter, inverter and anti-islanding scheme. At last we analyzed the future forecast of this system with respect to a typical household of Delhi city.

[6] [7] [8]

[9] [10] [11] [12] [13] [14] [15]

[16]

[17] [18] [19] [20] [21]

REFERENCES [1] [2] [3]

www.coal.nic.in www.sparastrategy.com www.newindianexpress.com published on 17th July 2013

MNRE Releases JNNSM Phase 2 Draft Policy Report; Targets 10GW of Utility Scale Solar Installations - Renew India Campaignsolar photovoltaic, Indian Solar News, Indian Wind News, Indian Wind Market. Renewindians.com (2012-12-03). Retrieved on 2013-12-06. India to unveil 20GW solar target under climate plan, Reuters, 28 July 2009. “India’s national solar plan under debate”. Pv-tech.org. Retrieved 2010-11-27. http://timesofindia.indiatimes.com/ Nitin Sethi, TNN, 18 November 2009, 12.42am IST (18 November 2009). T. Muneer, M. Asif and S. Munawwar, “Sustainable Production of Solar Electricity with particular reference to the Indian Economy ” Renewable and Sustainable Energy Reviews, Vol. 9,No. 5, 2005,pp. 444473. doi:10.1016/j.rser.2004.03.04. M. Mallikarjun, K. Praveena, ” An Effective Utilization of Concentrated Solar Energy” International Journal of Science Engineering and Advance Technology, September 2014. Mr. R. Narayanan Dr. R. Hamsalakshmi, “ FDI Opportunities in Indian Renewable Energy Sector” PARIPEX-INDIAN JOURNAL OF RESEARCH Volume : 3 ISSN - 2250-1991, April 2014. N. Sasikumar, Dr. P. Jayasubramaniam, “ Solar Energy System in India” IOSR Journal of Business and Management (IOSR-JBM) ISSN: 2278-487X. Volume 7, PP 61-68, Jan. - Feb. 2013 www.renewindians.com/2013/02 www.epia.org/ EPIA – European Photovoltaic Industry Association http://solar.smps.us Toshihiko Noguchi, Member, IEEE, Shigenori Togashi, and Ryo Nakamoto Short-Current Pulse-Based Maximum-PowerPointTracking Method for MultiplePhotovoltaic-andConverterModule System IEEE TRANSACTIONS ON INDUSTRIAL ELECTRONICS, VOL. 49, NO. 1, FEBRUARY 2002. K.H. Hussein, “Maximum photovoltaic power tracking: An algorithm for rapidly changing atmospheric conditions,” International Journal of Science Engineering and Advance Technology Vol. 142, no. 1, pp. 59–64, Jan. 1995. www.greenpeace.org/india/Global/india/report/2013/RooftopRevolution.pdf . http://dtl.gov.in/d/home.aspx http://rredc.nrel.gov/solar/calculators/PVWATTS/version Business Week, “What's Raining on Solar's Parade?” (February6, 2006),www.businessweek.com/magazine/content/06_06/b3970108. htm. Solar buzz, “2007 World PV Industry Report Highlights,” www.solarbuzz.com/Marketbuzz2007-intro.htm (accessed January 2008).

A Review of High Power Cycloconverter Applications for Synchronous Motor Drives in Mining Industries Nikhil Ashok Bari

Jitendra R. Rana

Electrical Department, MGM’s Jawaharlal Nehru Engineering College, Aurangabad, India e-mail: [email protected]

Electrical Department, MGM’s Jawaharlal Nehru Engineering College, Aurangabad, India e-mail: [email protected]

Abstract—Many advancements have taken place in control, analysis, modelling and practical implementation aspects of cycloconverters and their applications to the adjuslable-speed ac drives. This paper presents the theory of cycloconverter characteristics and attempts to make a comprehensive review on its application for synchronous motor drives in mining industries in which there are semiautogeneous grind mills and ball mills that require slow speed operation Keywords: Cycloconverter, Synchronous Motor Drives, Grind Mills, Ball Mills, Protection Scemes

I.

INTRODUCTION

The cycloconverter is a power-electronic equipment designed to convert constant voltage constant frequency ac power to adjustable voltage adjustable frequency ac power without any intermediate dc link. The basic principle of this converter is to construct an alternating voltage wave of lower frequency from successive voltage waves of a higher frequency rnultiphase ac supply by a switching arrangement. With the availability of large rating SCRs the cycloconverter today is a practical proposition in large power applications with synchronious motor and induction motors like gearless mill drive in cement industry, centrifugal pump and compressors and mining industries, electric traction, rolling mill, variable-speed constant frequency (VSCF) system ship propellers etc.

II.

is between 0.70 and 0.85 lagging (Fig. 3). Depicted of all these limitations, cycloconverters are still the preferred static converter for high power low speed synchronous motor drive applications

(a)

CYCLOCONVERTER CHARACTERISTICS REVIEW

This topic is reviewed from “High Power Cycloconverter for Mining Applications: Practical Recommendations for Operation, Protection and Compensation” published by P. Aravena, L. Morán, R. Burgos, P. Astudillo, C. Olivares. Cycloconverters are classified as direct ac to ac linecommutated frequency converters. Since they do not have an energy storage component, such as a dc capacitor or a dc reactor, the interaction between input and output terminals is direct (Fig. 1). An important operating characteristic of cycloconverters is that the output frequency is limited by current and voltage harmonic distortion and the maximum value cannot be higher than to 1/3 the line frequency. Another undesired characteristic of cycloconverters is that, even with a unity load power factor, the input power factor

(b) Fig. 1: Cycloconverter Power Circuit Configuration.(a) Simplified Threephase 6 Pulse Cycloconverter Topology. (b) Practical Implementation of Thyristors and Heat-sinks


Fig. 4: Cycloconverter Input Displacement Factor for Different Modulation Index Values and Unity Output Power Factor

Fig. 2: Typical Thyristors Arrangement in a 12 Pulse Cycloconverter

A. Input Power The amount of reactive power absorbed by the cycloconverter depends on the modulation index (r) and the load power factor, as shown in Fig. 3. Fig. 4 shows that the highest input displacement factor is close to 0.87 (lagging) and is achieved when the cycloconverter load operates at unity power factor and modulation index equals to 1.15. For a modulation index equals to 1, and rated output load power with unity power factor, the cycloconverter input power factor is 0.8 lagging. Figure 4 illustrates that for low output power operating conditions (low cycloconverter modulation index), the input power factor is quite low.

(a)

(b) Fig. 5: Input Active and Reactive Power for Different Cycloconverter Modulation Index Values. (a) Input Active Power as a Function of Different Cycloconverter Modulation Index. (b) Input Reactive Power as a Function of Different Cycloconverter Modulation Index

B. Current Harmonics

Fig. 3: Cycloconverter Input Displacement Power Factor as a Function of Output Load Displacement Power Factor for Different Modulation Index Values

Power absorbed by the cycloconverter for different modulation index values are shown in Fig. 5. These two figures show that the cycloconverter operates at almost constant input apparent power. At low modulation index operation (light load), more reactive power is absorbed by the cycloconverter (Fig. 5), while at higher modulation index, the active power absorbed by the cycloconverter increases (Fig. 4), and the reactive power decreases. This characteristic forces the compensation of a variable amount of reactive power, necessary to fulfill the distribution system power factor requirements, and to improve the voltage regulation.

Cycloconverter input current harmonic components can be classified as characteristics and non-characteristics. Characteristic harmonic components depend on the converter number of pulses, p, while non-characteristic components depend on the converter output frequency. The order of the input current characteristics and non characteristics harmonics is defined by (1) and (2).Equations

The total harmonic distortion is defined for integers multiples of the fundamental frequency, however it is possible to separate the THD associated with characteristics harmonics and non-characteristics harmonics as shown in (3) and (4) The total THD is calculated by using (5).

A Review of High Power Cycloconverter Applications for Synchronous Motor Drives in Mining Industries  57

the moment is forced to turn-on. In order to avoid commutation failures α+μ must be lower than 180°. Other parameters that influence the commutation process in the thyristor is the system voltage and frequency, and the system equivalent impedance referred at the cycloconverter terminals

Input current harmonic distortions generated by a 12 pulse cycloconverter and for different modulation index values, are shown in Figure 7 with technical data in Tables I, II and III. It is important to note that, for a given output frequency, the input current total THD is almost constant for all the modulation index range. Figure 7 shows that for operation close to rated load (modulation index higher than 1), the THD associated with non-characteristic harmonics is higher than the THD related with characteristic components design of the current harmonic compensation scheme.

Equation 6 also shows that in a weak power distribution system (large value of L) a large value of μ is required. Depending on power distribution system´s characteristics a safety commutation angle close to 10° or higher must be considered. Severe voltage drop at cycloconverter input terminals can also produce a commutation failure (6). Normally, undervoltage protections are included in the power distribution systems with a pick up adjusted at 85 % the rated value. If the voltage drop exceeds 15 %, the cycloconverter is turnedoff avoiding thyristors commutation failures as shown in Fig. 13. Based on thyristor commutation characteristics, most of commutation failures are caused by power distribution disturbance [1], [7]. Voltage drop and frequency variations increase the commutation angle required by the thyristors. If the voltage applied between anode and cathode is not high enough, the thyristor will not turn off, generating a commutation failure.

E. Fuseless and Snubber Circuits Fig. 6: Cycloconverter Input Current Total Harmonic Distortion for Different Modulation Index Values

C. Motor Starting Grinding mill drives use synchronous motors with current control technique (normally vector control). Vector control limits the stator current during motor starting at a value not higher than 150 %. Also, vector control forces the synchronous motor to operate with unity power factor. The motor starts using current control mode, until the speed reaches a value that can be measured by the encoder (70 % rated speed), and then changes to voltage control.

Figure 15 shows the typical snubber circuit configuration used in high power cycloconverters. RC-snubber circuits are used and connected in parallel to each thyristor. RC-snubber circuits are an important protection device which function is to limit dv/dt during the thyristor turn-on and turn-off. The snubber capacitor limits the voltage slope (dv/dt) during commutation, while the snubber resistor limits the capacitor current discharge (di/dt) during thyristor turn-on. In high power cycloconverters the snubber resistance are water cooling. Typical snubber C and R values are 0,22 mF and 36 Ω respectively (20 MW SAG mill drive). Figure also shows that each snubber circuits protect two thyristors, one of each anti-parallel converter.

D. Thyristor Commutation Thyristors are line-commutated semiconductors that can be controlled during the turn-on and not during turnoff process. Thyristor turn-off is achieved when voltage between anode and cathode is negative as well as the current (line commutation). In six pulse converters, as the one used in cycloconverters, the relation between the commutation process and the electrical parameters is given in (6), where μ is the angle required to commutate a given thyristor. In cycloconverters, the firing angle α, and the current Id are changing continuously, therefore the commutation angle required by each thyristor´s cycloconverter requires a different μ value, depending on

Fig. 7: Snubber Circuit Connection in a 12 Pulse Cycloconverter

Modern cycloconverters use fuseless thyristors, which means that are short circuit proof.


III. CYCLOCONVERTER PROTECTION SCHEME

IV. CONCLUSION

The following protections are implemented in SAG and ball mills:

Cycloconverter characteristics and protection scheme related with high power cycloconverters operation used in mining process have been reviewed and discussed in this paper.

1.

System over and undervoltage

2.

System frequency

3.

System overcurrent

4.

Differential protection at the motor side

5.

Motor air gap protection

6.

Ground fault protection

7.

Over load during motor starting

8.

Frozen charge shaken

To turn off the cycloconverter, thyristors gating signals must be removed before the main circuit breaker is open. Therefore, the cycloconverter control system must be coordinated with the power system protection scheme. A time delay equals to 100 ms must be implemented once the protection scheme trips, before the circuit breaker starts opening its contacts. Cycloconverter must be disconnected from the power grid after all thyristors have been turned-off.

ACKNOWLEDGMENT The author thanks Mr. B. T. Deshmukh Electrical Dept MGM’s Jawaharlal Nehru Engg College, Aurangabad and Mr. Mahesh Narkhede, Government Polytechnic, Nandurbar.

REFERENCES [1] [2] [3] [4] [5]

[6]

Fig. 8: The Protection and Control Scheme Block Diagram

Heydt, G.T.; Chu, R.F. (Apr. 2005). "The power quality impact of cycloconverter control strategies" IEEE Transactions on Power Delivery 20 (2):1711–1718. Power converter handbook, R.W. Lye, Power Delivery Department, Canadian General Electric Company, 1976. Bose, B.K., "Ore-Grinding Cycloconverter Drive Operation and Fault: My Experience with an Australian Grid," IEEE Industrial Electronics Magazine, Vol. 5, No. 4, pp. 12–22, Dec. 2011. T. Salzmann and H. Wokusch, "High-capacity cycloconverter drive for exacting dynamic requirements," Siemens Power Eng., pp. 339343, 1980. P. Syam, P.K. Nandi, and A.K. Chattopadhyay, “Improvement in power quality and a simple method of subharmonic suppression for a cycloconverter- fed synchronous motor drive,” Proc. Inst. Elect. Eng. B, vol. EPA, no. 4, pp. 292–303, July 2002. K.S. Smith, R. Yacamini, and A.C. Williamson, “Cycloconverter drives for ship propulsion,” Trans. Inst. Marine Engineers, pt. 1, vol. 105, pp. 23–52, 1993.

FACTS Technology: An Overview Anjali Atul Bhandakkar Lecturer in Electrical Engineering Department, Government Polytechnic, Pen, Maharashtra e-mail: [email protected] Abstract—The critical factor affecting power transmission today is power flow control. The increment in load variation in power transmission system can lead to potential failure of the entire system as the system has to work under stress. FACTS if integrated in power systems, control the power flow in specific lines and improve the security of transmission lines. With the use of modern controllable devices in electrical network, efficient, reliable, flexible and environmental sound transmission system can be achieved. With the high speed control of any one or two of electrical inter-related parameters like voltage, impedance, phase angle, current, active power, reactive power and with high speed electronic devices, beyond static VAR compensators and power system stabilizers, open up opportunities for enhancing the value of a transmission assets[1]. This paper presents the principle and comparison of various FACT devices, and also highlights the recent FACTS controllers and recent trends in FACTS technology. Keywords: FVSI, SVC, STATCOM, SSSC, IPFC, GIPFC, D-FACTS, VR, PAR, UPFC, DPFC

I.

INTRODUCTION

The term “FACTS” covers several power electronics based systems utilized in the AC power transmission and distribution to control the interrelated parameters. With the power demand on the rise, power transmission needs to be developed to corresponding pace [5]. When producers and consumers of electric energy produce and consume the electric energy in amounts that would cause transmission system to operate at or beyond one or more transfer limits, the system is said to ‘congested’. The action taken to reduce congestion is called congestion management. If congestion is not relieved then it may lead to tripping of overloaded lines, consequential tripping of other lines and in some cases to voltage stability problems. Hence to avoid such problem, congestion need to be solved. In this deregulated power market, Independent System Operator (ISO) has to relieve the congestion, so that the system is maintained in secure state. To relieve the congestion ISO can use one of the methods as operation of FACTS devices (preferably series devices) in the power system [2]. Also for the environmental and electrical reasons, it may be very well turn out impossible to obtain the necessary permits to build more transmission lines. A more intelligent way may be to take a fresh look at facilities already in place in the system and find ways for increased utilization of the said facilities. This is where FACTS is coming in.

FACTS solutions are particularly justifiable in applications requiring rapid dynamic response, ability for frequent variations in output and/ or smoothly adjustable output [3]. FACTS technology equipped with smart digital control systems offer an economic alternative and can be successfully employed to maintain and enhance bulk system dynamic reactive margin and address voltage stability related challenges. Investment in FACTS technology exhibit some desirable features that considerably increase their flexibility, modularity, scalability, short construction time, high levels of reversibility and small financial commitment. Also the load flow solutions incorporating FACTS devices are being performed in power system for planning operation, control and is useful to determine the overloading of particular elements in the system. It is also used to make sure that the generators run at the ideal operating point, which ensures that the demand will be met neither overloading the facilities nor compromising the security of the system or demand. This analysis gives information about, voltage magnitude and phase angle at each bus, real and reactive power flowing in each element, Reactive power loading on each generator [4]. Use of Genetic Algorithm (GA) and Particle Swarm Optimization (PSO) based approach gives optimal allocation and coordinated operation of multiple FACTS devices for economic operation as well as to increase power transfer capability of interconnected power system under different loading condition. FACTS devices can be subdivided in to three groups: shunt devices (SVC and STATCOM), series devices(TSSC, TCS and SSSC), and dynamic energy storage (shunt and series devices) as UPFC. FAST VOLTAGE STABILITY INDEX (FVSI): Voltage Stability is becoming an increasing source of concern in secure operating, of present day power system. The problem of voltage instability is mainly considered as the inability of the network to meet the load demand imposed in terms of inadequate reactive power support or active power transmission capability or both. FVSI is mainly concerned with the analysis and enhancement of steady state voltage stability based on L-index. When load bus approaches a steady state voltage collapse situation, the index L approaches numerical value is 1. Hence for an overall system voltage stability condition, the index evaluated at any of the buses must be less than unity. With FACTS devices in the network, the index value L is


determined which is an indication of how far the system is, from voltage collapse [5]. The selection of optimal location of FACTS controllers to maintain the voltage profile, minimize voltage deviation and to reduce real and reactive power losses can be determined using FVSI.

II.

SHUNT COMPENSATORS: SVC, STATCOM

Capacitors generate reactive power and reactors absorb when connected to ac power source. Using appropriate switch control, the VAR output can be controlled continuously from maximum capacitive to maximum inductive output at a given bus voltage. The different semiconductor power circuits, with their internal control, enabling them to produce VAR output proportional to an input reference, are termed as Static VAR generators (SVG).Static VAR compensator (SVC)is generator whose output is varied so as to control (varying the firing angle of the thyristor)specific parameters (e.g. frequency, voltage) of electric power system. The shunt compensator is functionally a controlled reactive current source which is connected in parallel with the transmission line to control its voltage [6]. SVC are also used to dampen power swings, improves transient stability, and reduce system losses by optimized reactive power control [7]. Also load flow studies on three phase transmission lines with unbalanced load, incorporating SVC is carried out which shows improvement in the unbalanced voltages, apart from maintaining better voltage profile. The role of SVC is to inject reactive power and maintain the voltage profile. It is also found that the real power loss and deviation in power flow is reduced during unbalanced condition [8]. Value of compensating device to be selected depends on many factors like: 1) Market availability of value of capacitor for a specific transmission line. 2) Excessive compensation leads to increased power transfer capability for which thermal rating of transmission line should be taken into account. 3) Available location for capacitor placement. 4) Expected increase in power transfer. 5) Transmission efficiency [12].

A. STATCOM STATCOM controls shunt compensation using converters operated as voltage & current sources and produce the reactive power essentially without reactive energy storage components(like capacitor banks or reactors) by circulating alternating current among the phases of ac system. A basic voltage-sourced convertor scheme (STATCOM) for reactive power generation, consists of dc input voltage source, provided by the charged capacitor and a relatively small tie reactance. The convertor produces a set of controllable three phase output

voltage with the frequency of ac power system. Each output voltage is in phase with and coupled to the corresponding ac system voltage via tie reactance. By varying the amplitude of output voltage produced, the real and reactive power exchange between the convertor and the ac system can be controlled [6]. When the unbalanced condition occurred in the power system, the losses in real and reactive power increase, affecting the system security. Performance analysis of STATCOM in real time Power System shows that during unbalanced condition, the connection of STATCOM reduces the losses of real and reactive power [13]. D-STATCOM can be used to correct voltage sag or voltage swell of any inductive network. Also maximum reactive current can be maintained even if system voltage is significantly depressed from its normal value. This is highly useful in situations where STATCOM is needed to support system stability during fault as well as after fault and stability issue would otherwise be a limiting factor on the power transmission capacity of the system. Results of two area power systems, when simulated with MATLAB/ Simulink environment, for a three phase symmetrical short circuit fault of 0.1 s, show that transient stability is improved better with STATCOM than SVC. Also post settling time of the system, after facing the disturbance is less than SVC where STATCOM is installed. Also better damping characteristics in rotor angle are achieved [9]. From practical point of view, STATCOM brings further important benefits such as: A small foot-print, due to replace of passive reactive components by compact electronic converters. Modular, factory assembled units reducing works, commissioning time, and cost. Natural relocability, due to modular and compact design, also low harmonic interaction with the grid.

III. SERIES COMPENSATORS: TSSC, TCSC, SSSC Series compensator (TCSC, TSSC) is functionally a controlled voltage source which is connected in series with the transmission line to control its current. It can be implemented either as variable reactive impedance or as controlled voltage source in series with the line [6]. Line reactance when decreased by adding capacitive reactance, increases real power flow and (line reactance) when increased, by adding inductive reactance in series with the line, increases reactive power flow. In the series compensation the basic reference parameter is the line current. TCSCs vary the electrical length of the compensated transmission line. Their proper location in transmission line results in maintaining power

FACTS Technology: An Overview  61

flow over pre-defined path, establishes alternative flow path under contingency conditions, manages line loading ensuring the optimal use of the transmission network, improves transmission system behavior with respect to voltage stability and angular stability and even reduces cost of generation. Location of TCSC: To determine location of TCSC, an index called contingency sensitivity index (CSI) is used for each branch. In general, the larger CSI value a branch has, the more sensitive it will be. The branch with the largest CSI is considered as the best location for placement of one TCSC. When more than one TCSC has to be installed, they will be chosen starting from the top of this ranked list and proceeding downward with as many branches as the number of available TCSCs. Particle Swarm Optimization (PSO) Algorithm gives optimal parameter settings of TCSC in order to eliminate or reduce the line overloads and bus voltage violation during single contingencies and to minimize the installation cost of TCSC [10]. However in adverse conditions, electrical resonance might be introduced which may under certain circumstances interact with mechanical torsional resonance in turbine-generator shaft systems in thermal power plant. This is known as sub-synchronous resonance. SSR condition may limit the degree of compensation needed for better power system performance [11]. The SSR issues could be eliminated by representing the device in an Inductive- Resistive mode. Degree of TSSC compensation ranges from 25 % to 75 %. The TCSC is more effective than the shunt controllers, as it offers greater controllability of the power flow in the line.

A. SSSC Impedance control can be realized by addition of series inverter equipped with energy storage in series with the transmission line. It consists of a solid state voltage source converter (VSC) which generates a controllable a c voltage at fundamental frequency [14]. When the injected voltage is kept in quadrature with the line current, it can emulate as inductive or capacitive reactance so as to influence the power flow through the transmission line. While the primary purpose of a SSSC is to control power flow in steady state, it can also improve transient stability of a power system. Fuzzy controllers can be used to control parameters of power system [15]. SSSC has to do two main functions. 1-compensates reactive power, 2-improves transient stability. Second functionality of SSSC system is due to its capability to raise it’s the maximum transferable electric power from generator to infinite bus. To raise the maximum transferable electric power, the SSSC actively and

appropriately changes the line reactance [16]. Since control of power system is a non-linear problem, therefore non-linear controller for SSSC are designed. The proposed nonlinear controller of the SSSC increases the critical clearing time of the power system faults and damps out rotor oscillations of single machine connected to infinite Bus. Analytical and simulation results of application of distance relays for protection of transmission line employing SSSC has been provided. First the detailed model of SSSC and its control is proposed and then situation is studied analytically, where errors introduced in impedance measurement due to the presence of SSSC on the line is analyzed. The simulation results show the impact of SSSC on the performance of distance protection relay for different fault condition, influence of operational mode of SSSC, its location on the transmission system and fault resistance. SSSC when employed with fuzzy controller, the simulation results show that this controller gives the best non-linear system performance. Fuzzy controller can achieve oscillations damping, fast response, and finally stabilizing power system[15] All these factors are to be taken into account while installing SSSC in the power system.

IV. UPFC UPFC is a combination of STATCOM and SSSC which are coupled via a common dc link, to allow a bidirectional flow of real power between the series output terminals of SSSC and the shunt output terminals of STATCOM. They are controlled to provide real and reactive series line compensation without an external electric energy source. UPFC will concurrently or selectively control the transmission line voltage, impedance and angle and alternatively the real and reactive power flow in the transmission line with reduced transmission losses. The UPFC also improves transient stability and fast steady state achievement and lessens the congestion. Among the FACTS devices, UPFC is the most complete and advanced controller. The UPFC is modelled as two controllable voltage sources, series inverter and shunt inverter. Two perpendicular components, one in-phase with the system bus voltage and the other in quadrature are used to represent both compensation voltages generated by each inverter of the UPFC [17]. Various controllers have been proposed to regulate the operation of UPFC. Adaptive Neuro Fuzzy Inference Controller (ANFIC) is based on the first-order Takagi– Sugeno model and enables only a single output. From the


simulation output, it is clear that proposed ANFIC controller shows good performance in controlling real and reactive power flow. The system response obtained for different short circuit levels shows the capability of the UPFC to regulate the power flow and maintain stability by ANFIC controller [18]. Also Matrix Converter based Unified Power Flow Controller are being developed. The concept of UPFC is based on back to back connection of two inverters with a common capacitor dc link. The two converters and the capacitor in the UPFC’s structure are replaced with a dualbridge matrix converter. Matrix converter allows direct ac to ac power conversion without DC energy storage links, which results in considerable decrease in UPFC’s cost and volume. These converters are capable of performing the same ac/ac conversion, allowing bidirectional power flow, guaranteeing near to sinusoidal input and output currents, voltages with variable amplitude, and adjustable power factor. These minimum energy storage ac/ ac converters have the capability to allow independent reactive control on the UPFC shunt and series converter sides, while guaranteeing that the active power exchanged on the UPFC series connection is always supplied/ absorbed by the shunt connection [19]. DPFC- Distributed Power Flow Controller can be considered as UPFC with eliminated common DC link. In DPFC exchange of active power between shunt and series converter is done through transmission line at third harmonic frequency. DPFC consists one shunt converter as STATCOM while series converter uses DSSC concept i.e. multiple single phase series converters with its own capacitor in order to provide required DC voltage [20].Within the DPFC, the transmission line is used as a connection between the DC terminal of shunt converter and AC terminal of series converters, instead of direct connection using DC link for power exchange between converters. Here zero sequence control strategy is used to control active power. The third harmonic (V & I) is used for exchange of active power. The total cost of DPFC is much less than UPFC because high voltage isolation is not required at the series converter part and rating of components is also low. High control capability, reliability is achieved. Fuzzy based zero sequence control strategy proves acceptable performance in power quality, power flow control when simulated with three phase fault near the load [21].

V. COMPARISON OF VARIOUS FACTS CONTROLLERS Table 1 shows the comparison of various FACTS controllers in terms of the mathematical model, their various attributes etc.

TABLE 1: COMPARISON OF VARIOUS FACTS CONTROLLERS Parameter

Shunt Series Dynamic Controller Controller Controller Types TCR,TSR, TCSR,TCSC, UPFC, TCPST, DPFC, TSC, FCSSSC IPFC,GIPFC TCR, STATCOM Mathematic Variable Variable Variable current & al Model Susceptance Impedance voltage source (shunt (controlled (controlled &series controller) reactive voltage current source) source) Placement Near the Near the Slightly Off-Centre of the load end for sending end device the radial bus feeder, middle for long TL or Connecting two systems Attributes VC,DO,TS, PC,TS,DO,SI VC,PC,TSDO,PAC,VA VAR Comp C R Comp, VC-Voltage Control; SIC-Series Impedance Control; DO-Damping of Oscillation; TL-transmission Line TS-Transient stability; PAC-Phase Angle Control VAR Comp-VAR Compensation; PC-Power Control

VI. D-FACTS Series FACTS controller required for power flow control, high fault currents, basic insulation requirements, stresses the power electronics system, thus making FACTS installation costly and not reliable. Distributed Series FACTS controller is a reliable option for lumped series FACTS controller. Distributed Static Series Compensator (DSSC) is nothing but SSSC with reduced power rating. Instead of high power conventional SSSC, number of low power DSSC modules are clamped around the conductor. Each DSSC module consists of small rated single phase inverter and a single turn transformer STT) that is mechanically clamped on to existing transmission line. DSSC controls effective impedance of the transmission line by injecting voltage in series with the line so as to control active power flow. Inverter controls the voltage injected that is orthogonal to the line current in the power system. DSSC module is self-powered. As the module is to be clamped to the line, it does not need to meet BIL (Basic Insulation Level) limit. With high turns ratio, secondary current level is reduced. Hence power semiconductor device rating is reduced, resulting in reducing stress on power electronics devices & overall cost. With proper STT design with proper selection of core material, weight of DSSC will be acceptable for installation [14].

A. Voltage Regulator and Phase Angle Regulator(VR & PAR) The basic concept of the voltage and phase angle regulation is the addition of an appropriate (with controllable amplitude) in-phase or a quadrature

FACTS Technology: An Overview  63

component to the prevailing terminal (bus) voltage in order to change its magnitude or phase angle to the specified. Thus PAR can be considered as a sinusoidal (fundamental frequency) ac voltage source with controllable amplitude and phase angle. If the angle of injected phasor relative to the terminal voltage is ±90⁰, then PAR becomes a Quadrature Booster. With Quadrature Booster Regulator, maximum transmittable power increases with injected voltage, and magnitude of sending end voltage. VR and PAR are connected where two or more than two transmission lines are interconnected or connected in parallel, resulting in one or more circuit loops with the potential for circulating current. The distribution of real power flow over interconnections forming loop circuit can be controlled by PAR. Flow of reactive power flow can be controlled by VR. This is achieved as PAR injects a quadrature voltage in series with the circuitloop resulting in the flow of inphase circulating current and VR introduces a series inphase voltage into theloop and quadrature current is circulated through the loop since the impedances are substantially reactive. Thus insertion of PAR in any one line can correct the difference in quadrature voltage drops and can control the real power distribution between the lines. An added Voltage Regulator can cancel the in-phase voltage difference and controls the reactive power flow. Both VR and PAR provide major benefits for multiline and meshed systems, the full utilization of transmission assets (decrease of reactive power flow, control and balance of real power flow) reduction of overall system losses through the elimination of circulating loop currents. Also VR plays an important role in voltage levels in sub-transmission and distribution systems in maintaining operating level. PAR with appropriate control capability to counteract prevailing machine swings can improve transient stability and provide power oscillation damping. Use of TC-VAR and TC-PAR eliminates the expensive regular maintenance & provides high speed response [6].

lines for power flow optimization. In case of Generalized IPFC (GIPFC) an additional VSC is connected in shunt with the test system and another end is connected in parallel to the common DC link capacitor which will improve the performance of the controller and overall system operation. Reactive power flow control can be obtained independently by series converters whereas the real power flowing into or out of each converter has to be coordinated in such a way that the DC link voltage is kept constant and hence the overall surplus power from underutilized lines can be used by over loaded lines for real power compensation. In other words VSC can inject a current vector into the transmission line in such a way to maintain voltage across the capacitor constant to achieve continuous reactive power compensation. A limited real power compensation for short duration is also possible [22].

VII. FACTORS LIMITING THE WIDESPREAD APPLICATIONS OF FACTS TECHNOLOGY FACTS and power flow controlling devices are of international interest today, thanks to recent technological advances and have found their applications in many T&D networks. These devices solve problems in active and reactive power- flow control and network stability. In spite of rising devices of FACT devices, there are a few factors that have been limiting the widespread application of this technology, prominent being the following: 

The lack of clear understanding of different options of devices and their configuration & their suitability for solutions of different network problems.



The lack of information on systematic approaches towards economic assessment of FACTS projects for utilities & transmission entities



The lack of information on analysis and comparison as well as long term system-wide alternatives for utilities faced with transmission reinforcement. [13]

B. IPFC, GIPFC First Generation Voltage Source Converter based FACTS controllers STATCOM, SSSC does not use bulk capacitor or inductor. Second generation of convertor based FACTS controller UPFC has all merits of STATCOM and SSSC but the only demerit is that every transmission line needs independent UPFC which increases system complexity and the cost. This drawback can be overcome by the third generation convertor based FACTS controller namely Interline Power Flow Controller (IPFC) which targets the problem of compensating a number of transmission lines at a given substation. The IPFC is the combination of two or more number of SSSC connected in series with different transmission lines and they share a common DC link capacitor & hence able to control power flow from overloaded lines to under loaded

VIII.

SCOPE OF INVESTIGATION



To conduct a detailed network study and investigate the critical conditions of grid connections. These conditions could include risks of voltage problems or even voltage collapse, undesired power flows as well as the potential for power swings or sub-synchronous resonances and suggest FACTS controllers.



For a stable grid, the optimized utilization of the transmission lines, increasing energy transmission capability limit using FACTS controllers.




If there is potential for improving the transmission system, either through enhanced stability or energy transfer capability, the appropriate FACTS device and its required rating can be determined.



Based on the technical information, an economical study can be performed to compare type of FACTS devices or conventional solutions with achievable benefits.



Selecting a FACTS controller, deciding its location, cost analysis for improving power system stability and economy.

[1] [2]



Dynamic performance & voltage control analysis will continue to be a very important process to identify system problems and find the possible solutions.

[3]





To perform contingency analysis for taking preventive action of the power system, for generator outage, transformer outage or single or multiple transmission lines outage and deciding controller, its settings &location. To propose Matrix Converter based UPFC to control active and reactive power flow to desired limit on complex multi-machine system irrespective of load changes.

effective. There are several methods for finding optimal location of FACTS devices in both vertically integrated and unbundled power systems like L-index method, sensitivity methods, Reactive power spot price index method and intelligent methods like Fuzzy methods, Genetic Algorithm, Particle Swarm Optimization, MATLAB/Simulink etc to adapt the FACTS Technology efficiently [23].

REFERENCES

[4]

[5]

[6] [7]

IX. CONCLUSION This paper has presented overview of FACTS controllers, recent trends in field. FACTS, new controller technology, based on power electronics & also scope of investigation. FACTS offers an opportunity to enhance controllability, considerably increased operating margins required for maintaining stability, power transfer capability and ensure better quality in modern power systems. The application of FACTS controllers throws up new challenges for power engineers, not only in hardware implementation, but also in design of robust control systems, planning and analysis. There has been considerable progress in the application of FACTS controllers. FACTS do not indicate a particular controller but a host of controllers that the system planner can choose, based on cost benefit analysis. The necessity to design electric power networks providing the maximal transmission capacity and at the same time resulting in minimal costs is a great engineering challenge for which a powerful solution is FACTS controllers. Third generation FACTS controller (GIPFC) enables control over multiple transmission lines for improved voltage profile and power factor. There is every reason to believe that in a decade or so, FACTS controllers and/or D-FACTS controller will revolutionize electrical power transmission systems making them more reliable, optimally utilized and better controlled and cost

[8]

[9]

[10]

[11]

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[14]

[15]

Narain G. Hingorani, “FACTS Technology and Opportunities”. Dipak S. Yeole, Dr. P.K. Katti, “FACTS device allocation for Transmission Congestion Management in Deregulated Power Market”, IOSR Journal of Electrical Electronics Engineering, pp. 07-12, The National conference on ‘Electrical Engineering Research & Advancement’ (EERA-2014). Rolf Grunbaum, Martin de Grijip, Valbert Moshi, “Enabling Long Distance AC Power Transmission by means of FACTS”, IEEE AFRICON 2009, 23-25 september, Nairobi, Keya. K. Sundararajau, Dr. A. Nirmalkumar, A. NnandhaKumar, S. Jeeva, “Performance Analysis of STATCOM in Real Time power system”. International Conference on Advances in Electrical Engineering, (ICAEE 2014), Vellore, January 2014. Kiran Kumar Kuthadi, K. Silpa Devi, “Analysis and Enhancement of Voltage Stability using Shunt Controlled FACTs Controller”, International Journal of Research in Electrical & Electronics Engineering Volume 1, Issue 2, pp. 25-33, October-December 2013. N.G. Hingorani and L. Gyugyi, Understanding FACTS, IEEE Press. Pradeep Kumar S. Mahapure, A.R. Soman, “Comparison of FACTS Devices for Power System Transient Stability Improvement”, International Journal of Innovative Research in Electrical, Electronics, Instrumentation and Control Engineering, Vol. 2, Issue 6, June 2014. Karthik B., Arokkia Jerald Praveen, Serrjith S., Shriram S. Rangarajan, “Three Phase Power Flow Incorporating Static VAR Compensator”, Applied Mechanics and Material Vol. 573(2014) pp. 747–756. Naimul Hasan, B.B. Arora, J.N. Rai, “Comparison of FACTS for two Area Power System Stability Enhancement using MATLAB Modelling”, IJEET, Volume 5, Issue 8, pp. 41-52, August 2014. S. Raju, G. Madhavi, “Optimal Location and Parameter Settings of TCSC under Single Line Contingency using PSO Technique”, International Journal of Scientific & Engineering Research, Volume 5, Issue 3, March, 2014. Hans- Ake Jonsson, “FACTS: Transmission Solution in changing world”, Power system Technology,2000, Proceedings, power Con 2000, international Conference,Vol. 3, 4-7 December 2000, IEEE. Syona Chawla, SheetalGarg, Bhavna Ahuja, “Optimal Location of Series-Shunt FACTS Devices for Transmission Line Compensation”, Control, Automation, Communication and Energy Conservation,2009, International Conference at Perundurai, Tamilnadu.* Badri Ramanathan, David Elizonda, Johan Enslin and Li Zhang, “Cost Effective FACTS Solution for Transmission Enhancement and its Economic Assessment”, Transmissin and distribution Conference and Exposition, Latin America, 2006,15-18 August 2006, 2006 IEEE. Mr. Sandeep R. Gaigowal, Dr. M.M. Renge, “Some studies of Distributed Series FACTS Controller to control active power flow through Transmission Line”, 2013 International Conference on Power, Energy and Control(ICPEC), 6-8 Feb., Sri Rangalatchum Dindigul, 2013 IEEE. Anjali S. and Padmavathi D, “Stability Enhancement of Multi Machine system with FACTS device SSSC using Fuzzy logic”, Research Journal of Engineering Sciences, Vol. 3(9), 12-20, September 2014.

FACTS Technology: An Overview  65 [16] V. Kakkar, N.K. Agarwall, “Recent Trends in FACTS and DFACTS”, Proceedings of International Symposium on Modern Electric Power Systems, Wroclaw, Poland, Sept. [17] M. Asrar Ur Rahman and M. Sabah ul Islam, “Voltage Control and Dynamic Performance of Power Transmission Using Static VAR Compensator”. International Journal of Interdisciplinary and multidisciplinary Studies (IJIMS), Vol. 1.2014. [18] B. Gopinath, Dr. S. Suresh Kumar, Juvan Michael,”Implementation of Unified Power Flow Controller (UPFC) for Stability Analysis in Power System using Advanced control Techniques”, International Journal of Modern Electronics and Communication Engineering, (IJMECE) Volume No.-1, Issue No.-1, March, 2013. [19] Amjed M, Prof. Lathika B. S. “Matrix Converter based Unified Power Flow Controller”, International Conference on Power, Signals, Controls and Computation (EPSCICON), 8-10 January 2014. [20] CH. Ramaya, B. Shankar, “Improvement of Voltage Quality Using Distributed Power Flow Controller”, International Journal of Technology & Engineering Science [IJTES] Volume 2 [8], pp. 2185–2189, August 2014. [21] Shraddha Ramani, B. Anjanee Kumar, “FUZZY Based Zero Sequence Control Strategy for Enhancement of Power Quality in Distribution System by DPFC”, International J Journal of Professional Engineering Studies, Vol. IV, Issue 1 / Sept-2014. [22] A. Saraswathi, S. Sutha, “Investigation of Modified Generalized Interline Power Flow Controller (GIPFC) and Performance analysis”, Applied Mechanics and Material Vol. 622 pp. 111-120, August 2014. [23] Sunil N Malival1, Prof. Y.R. Prajapati, “Optimal Location and Cost Analysis of TCSC For Improving Power System Stability & Economy”, International Journal of Advance Engineering and Research Development (IJAERD) Volume 1, Issue 5, May 2014. [24] R. Grunbaum, P. Andersson, “ FACTS-Intelligent Solution for Meeting Challenges in Power Transmission”, IEEE PES Power Africa-2012-Conferenceand Exposition Johannesburg, South Africa, 9-13 July 2012,IEEE. 2012. [25] Therese Uzochukwuamaka Okeke and Ramy Georgious Zaher, “Flexible AC Transmission Systems (FACTS)” IEEE-2013.

[26] A. Edris, “FACTS Technology Development: An Update”, IEEE Power Engineering Review, IEEE, Vol. 20, Issue 3, pp. 4-9, March 2000. [27] D.G. Ramey, M. Handerson, “Overview of a Special Publication on Transmission System Application Requirments for FACTS controllers”, IEEE Power Engineering Society General Meeting, Tampa, FL, pp. 1-5, June 2007. [28] Preeti Singh, Mrs. Lini Mathew, Prof. S. Chatterji, “MATLAB Based Simulation of TCSC FACTS Controller”, Proceedings of 2nd National Conference on Challenges & Opportunities in Information Tech. (COIT-2008) RIMT-IET, Mandi Gobindgarh. March 29, 2008. [29] Lini Mathew, S. Chaterji, “Transient Stability Analysis of MultiMachine System Equipped with Hybrid Power Flow controller”, IJCEM International Journal of Computational Engineering & Management, Vol. 15 Issue 4, July 2012. [30] Vaishali Pawade, Lini Mathew, S. Chatterji, “Lab VIEW Based Simulation of UPFC incorporated on Multi- Machine System”, IOSR Journal of Electrical and Electronics Engineering (IOSR-JEEE). [31] Bhaskar Ray, “FACTS Technology Application to Retire Aging Transmission Assets and Address Volttage Stability Related Reliability and .Challenges in San Francisco Bay Area”, Transmission and Distribution Conference and Exposition, 2003, Vol. 3, pp. 1162-1169, 7–12 September 2003, 2003 IEEE. [32] .L.F.W.de Souza, H. Watanabe, J.E.R. Alives L.A.S. Pilotto, “Thyristor and Gate Controlled Series Capacitor: Comparison of Component srating”, IEEE Transactions on Power Delivery, Vol. 23, Issue. 2, pp. 899-906, April 2008. [33] Gerardo A. Blanco, Fernando G. Olsina, Olvasdo A. Ojeda “Transmission Expansion planning under Uncertainty-The Role of FACTS in providing strategic flexibility”, IEEE Bucharest Power Technology Conference, Bucharest, Romania, June, 2009. [34] Chandni B. Shah, “Voltage Improvement using SHUNT FACTS Device: STATCOM”, International Journal of Engineering Development and Research (IJEDR), Vol. 2, Issue 2, pp. 22672272, June 2014.

Exploiting Cloud Computing for Smart Grid Applications: A Review Aditya Bhardwaj

Maitreyee Dutta

ME (CSE) Student, Computer Science Department, NITTTR, Chandigarh, India e-mail: [email protected]

Professor & Head, Computer Science Department, NITTTR, Chandigarh, India e-mail: [email protected]

Amit Doegar Assistant Professor, Computer Science Department, NITTTR, Chandigarh, India e-mail: [email protected] Abstract—To meet the Electric Power demands of a fast expanding economy, smart grids (SGs) are expected to have reliable, efficient, secured and cost-effective power management system. Additionally, energy demands from the users change dynamically in different time-periods (such as on-peak, and off-peak), which required dynamically availability of the communication facility (such as bandwidth, storage devices and processing units). Therefore, there is a need to integrate to a common platform with the smart grid which is able to support the smart grid requirements. To focus on these requirements, we provide a review on cloud computing applications for the smart grid architecture, in two different areas-energy management, and information management. This paper could pave a good background for smart grid developer in decision making in these areas. Keywords: Cloud Computing, Smart Grid, Energy Management, Information Management

I.

INTRODUCTION

The world is looking for utility of cloud computing for the development of smart grid (SG).Cloud Computing is probably the simplest and best fitted way for smart grid (SG) due to its scalable and flexible characteristics, and its capability to manage large amount of data. Any smart grid (SG) infrastructure should support monitoring, analysis, control, and communication capabilities to the conventional Power Grid System to maximize the throughput of the system and reduce the energy consumption. The existing power grids need optimal balancing of electricity demand and supply between the consumers and the utility providers. So, Energy management needs to be addressed with the implementation of cloud computing in smart grid (SG). The overwhelming heterogeneous information generated in the smart grid (SG) due to widely deployed monitoring, metering, and measurement calls for a powerful and cost-effective information management mechanism for data processing, analysis and storage. Hence, we explore how cloud computing, a nextgeneration computing paradigm serves the information management in the smart grid (SG).

In this respect, cloud computing can play key roles of motivation in the design of smart grid (SG). Cloud Providers facilitate cloud computing and offer services with their huge servers for computations and with their bid data centers for storage. This paper is organized as follows. In section II overview of cloud computing is presented. In section III and IV smart grid (SG) overview and its Framework is described. In section V analysis of cloud computing for smart grid (SG) applications is presented.Finally this paper is conclude in section VI.

II.

OVERVIEW OF CLOUD COMPUTING

A. Definition Cloud computing is an emerging computing technology that provides on-demand facilities and shared resources over the internet. Cloud computing started gaining general popularity in 2006 when Amazon launched its Elastic Compute Cloud (EC2) as a commercial web service, allowing small businesses and individuals to rent computing resources [1]. In the simplest terms, cloud computing means storing and accessing data and programs over the Internet instead of your computer’s hard drive. In cloud computing, the word “cloud” is used as a metaphor for “the Internet”. Although there are many different definitions for cloud computing, there is a broad consensus on the definition by the National Institute of Standards and Technology (NIST). According to the NIST “cloud computing is a model for enabling convenient, on-demand network access to a shared pool of configurable computing resources ( e.g. networks, servers, storage, applications, and resources) that can be rapidly provisioned and released with minimal management effort or service provider interaction [2].

Exploiting Cloud C Computin ng for Smart Griid Applications: A Review  67 7 TABLE 2: FOUR DIFFERENT CLOUD D DEPLOYMENT MODELS [5]

B. Cloud Computing C Seervice Modell Cloud Seervice Modells are the refference modells on which the cloud c computting is basedd. These cann be categorized into i three baasic service models as listed l below: TABLLE 1: THREE DIFFERENT SERVICE MODELS [3] Service Modelss Servicce Offered IaaS IaaS offers harrdware platform (Infrastructure (computing poower, storage andd as a Service) network) to thhe users ondemand basis.. PaaS PaaS, provides a development (Platform as a platform to assist application Servie) design, develoopment, testing, deployment,onn the cloud. SaaS Software is prresented to the ennd (Software as a users as servicce on demand in a Servie) browser.

Examplee Amazon EC2, Microsoft Azuure Platform Google App Engine, Microosoft Azure Salesforce.com m Google App

Dep ployment Featurees Model M Privaate Cloud Cloudd is owned or rennted by a privatte organization. T The purpose of this tyype of cloud is too serve its own businness applications Public Cloud Cloudd is owned by a sservice proviider, and its resouurces are sold to thee public. Com mmunity Simillar to the private ccloud model, Clou ud here cloud c resources aare shared amonng members of a cclosed comm munity with simillar interests. Hybrrid Cloud It is thhe combination oof private, public, and communityy clouds

Example Eucalyptus, E Elastra, E

Amazon, A Google, and Microsoft M Google Apps for Government

Amazon A S3

D. Characteristtics of Cloudd Computing Technology The essential characteristiccs of cloud computing cann be ellaborated in Table3 T as folloows: TAB BLE 3: DIFFERENT T CHARACTERISTICS OF CLOUD TECHNOLOGY E [6]

Fig. 1: Cloud Computinng Service Deliverry Models [4]

C. Cloud Deployment D M Models Cloud deeployment moodel define thee type of acceess to the cloud i.e how h the cloudd is located? Cloud C can have any of the four tyypes of accesss: Private, Public, P Hybridd and Community

Name N D Description Scalaability User can c expand and reeduce resources according a to and Elasticity E speciffic service requireement. Natu ure On-d demand Consumer can unilaterrally provision co omputing capabilities Broaad Resouurces are available over the networrk and accessed netw work througgh standard mechhanisms in large scale. s accesss MulttiCloudd services provideers host the servicces for multiple tenan ncy users within the same iinfrastructure. Reso ource Servicce provider’s com mputing resourcess are pooled pooliing togethher, with differentt physical and virrtual resources dynam mically assigned aand reassigned acccording to consuumer demand Resilliency Resiliiency is the abilityy of a serverr, network, storagge system, or an entire e data centerr, to continue opeerating even when n there has been an equuipment failure, ppower outage or other o disruption.

III. OVE ERVIEW OF SMART GRID (SG) A. Definition D Smart grid iss capable of delivering eleectricity moree efficiently and relliably than thhe conventional power gridd systeem. It I consists off power netwoork composed d of intelligentt nodees that can operate, coommunicate, and interactt auton nomously, in order to efficciently deliverr electricity too the customers. c g is introdduced to maake the gridd So, smart grid operaation smarter and intelligennt.

Fig. 2: 2 Cloud Computting Deployment Models [4]

Smart Grid is i defined as “It is the neext-generationn electtrical power-ssystem that m manages electrricity demandd in a sustainable, reliable r and eeconomic man nner, built onn advaanced infrastruucture”


B. Need for Smart Grid Existing power grid systems are under pressure to deliver the growing demand for power, as well as provide a stable and sustainable supply of electricity. These challenges are driving the evolution of smart grid technologies. Other reasons for the need of smart grid are: 

Increasing energy efficiency.



Inadequate access to electricity.



More reliability.



Better Management of Peak Load.

C. Benefits of Smart Grid Smart Grid (SG), combines information technology with power transmission to benefit your home, community, and your nation. Other Benefits of smart grid (SG) are:

1. Benefits to Consumers: 

On-demand supply.



Dynamic pricing.



Gives control over power bill.

Integration

There is optimization, standardization and refinement of the management paradigm Compatibility There is provision of centralized power generation, distributed power generation and energy storage capabilities Self-heals The smart grid (SG) monitors itself and automatically detects, analyzes, responds and restores grid components to maintain reliability, security, and power quality. Accommodates all Smart grid (SG) accommodate a portfolio of Generation and diverse generation types analogues to plug-andStorage Options play in today’s computer environment.

IV. SMART GRID FRAMEWORK The smart grid (SG) framework is composed of seven domains, which are complaint with the standards defined by the National Institute of Standards and Technology (NIST) [8]. This smart grid (SG) framework is a set of view and descriptions that are the basis for discussing the characteristics, uses, behavior, interfaces, requirements, and standards of the smart grid (SG). Actors in the framework may be devices, computer systems or software programs or the organization that own them. Actors have the capability to make decisions and exchange information with other actors through interfaces.



Reduced operational costs.

To enable smart grid (SG) functionality, the actors in a particular domain interact with the actors in other domains as shown in Fig. 3.



Increased employee safety.

TABLE 5: DOMAINS IN SG FRAMEWORK [8]



Higher customer satisfaction.



Reduced capital costs.

2. Benefits to Utility & Government Providers:

3. Benefits to Environment: 

Opportunity to improve environmental leadership image in the area of improving air quality.



Reduction in frequency of transformer fires through the use of advanced equipment prevention technologies.

Domain Bulk Generation Transmission Distribution Customers

Markets Service Providers Operations

Actors in the Domain Responsible for the bulk generation of electricity. May also store energy for later distribution. Carriers of bulk electricity over long distance. The distribution of electricity between transmission system and the customer. The end users of electricity. Customers may also manage the use of energy. Customers may be home, industrial, and commercial Includes operators and participants in electricity markets Organizations providing services to electrical customers and utilities. The managers of the movement of electricity

D. Smart Grid Characteristics If smart grid (SG) is designed and operated with the following characteristics at the core, then the grid would significantly improve in reliability, efficiency, and support to the consumers. The essential characteristics of smart grid (SG) can be elaborated in Table4 as follows: TABLE 4: FEATURES OF SMART GRID (SG) [7] Features Interactive

Optimizes Assets and Operates Efficiently

Description There is intelligent interaction between utility grids and end-users to achieve energy flow, and information flow. Assets will be managed in concert so that, as a system, they can deliver functionality at minimum cost.

A.

Connection between Cloud Computing and Smart Grid Domain

Cloud computing domain offers storage, validation, optimization of various data to the smart grid (SG) domain as pay-as-you-go and on-demand services. The six actors (customer, market, bulk generation, transmission, distribution, and operations) of the smart grid (SG) domain–work as the end users in the cloud computing domain. These six actors of the smart grid (SG) domain analyze their information requirements and ask for solutions in the cloud computing domain as end users. The connections are shown by lines 1-6 in Fig. 3.

Exploiting Cloud Computing for Smart Grid Applications: A Review  69

The actors in the cloud computing domain are responsible for the maintenance, optimization and upgrade of such services. If the services or applications requested by the actors in the smart grid (SG) domain do not exist, the cloud computing providers need to design and deploy these new services. The cost of Update, upgrade and maintenance can also be cut down, since the cloud computing service providers will take care of these tasks. The connections shown by lines 7-8 in Fig. 3 shows that smart grid (SG) service providers may work as end users or even cloud computing service providers because smart grid (SG) service providers may also design the corresponding applications and services by using the cloud computing architecture.

V. ANALYSIS OF CLOUD COMPUTING FOR SMART GRID APPLICATIONS This section analyzes the integration of cloud computing for smart grid applications and show how

cloud computing can be used for smart grid (SG) applications in terms of energy management, information management, and security management.

A. Energy Management Analysis Energy management is a broader term, which applies differently in different scenarios, but in smart grid (SG) we are concerned about energy saving in home, organization or business. The primary objective of smart grid (SG) is to support cost-effective and reliable energy management in realtime. In this section, we provide a brief overview of problems in existing approach for energy management without cloud applications and then how these problems can be solved with the implementation of cloud computing for energy management in smart grid (SG).

Fig. 3: Connection between Cloud Computing and Smart Grid (SG) Domains [8] TABLE 6: SUMMARY OF CLOUD COMPUTING APPLICATIONS FOR SMART GRID (SG) ENERGY MANAGEMENT Smart Grid Features Demand Response (as in [9])

Purpose

Problems with Existing Approaches without Cloud Due to limited memory and storage, it will be challenging for energy management when the number of customer increases Due to limited bandwidth resources, real time implementation is quite difficult Computational delay

Real-time-monitoring (as in [10])

Demand response are the actions voluntarily taken by a consumer to adjust the amount or timing of his energy consumption Monitoring and controlling real-time electrical demands.

Micro-grid management (as in [11])

Software is presented to the end users as service on demand in a browser

Information interaction using Mobile agent

Mobile agent decide when and where to move

Poor information interaction mechanism of power system

Dynamic pricing and Peak demand

During peak-hour, the allotted bandwidth is higher than that in the non-peak hour, so as to serve all incoming jobs simultaneously

Not supported

Solution with Cloud Computing Technologies Two cloud-based demand response models are: a)data-centric communication b) topic-based group communication There is support of dynamic and always-on applications To minimize the computational delay External computing devices are integrated with the internal computing devices Combination of mobile agent and cloud computing is used to serve the information interaction mechanism of power system Incoming jobs are scheduled to be executed according to the available resources, and job priority


B. Information Management Analysis Information sharing is one of the most important issues in a smart grid (SG). Information from different components, and the supply and demand state conditions can be shared with the help of cloud computing. TABLE 7: SUMMARY OF CLOUD COMPUTING APPLICATIONS FOR SMART GRID (SG) INFORMATION MANAGEMENT Smart Grid Purpose Features Cloud data Cloud data warehouse is warehouse defined in terms of (as in [12]) ETL(extract transform load), OLAP (online analytical processing), DM(data mining), BI (business intelligence) Smart meter A smart meter is a key data streams component in the smart grid in cloud architecture. With a smart meter, you can see how much energy you use so you can make changes to save money on your electric bills. Smart grid Used for Real-time data cloud distributed data (as in [13]) management and parallel processing of information Dynamic Cloud based data centers are data centers served as dynamic data operations centers

Cloud Computing Applications Cloud data warehouse provides different services for smart grid information management such as data mining and multi-dimensional data analysis Cloud provides IaaS (Infrastructure as a Service) for processing smart meter data.

Thus, the integration of cloud computing with smart grid (SG) is envisioned to be useful for evolving the smart grid in terms of considerations such as monitoring cost, energy management, and information management.

REFERENCES [1]

[2]

[3]

[4]

[5]

Cloud provides PaaS (Platform as a Service) for smart grid data cloud Cloud computing services are used to store the realtime information from the smart meters.

[6]

[7]

[8]

VI. CONCLUSION [9]

From this reviewed work, we can see that use of cloud computing applications in smart grid (SG) is one of the useful techniques to overcome the issues related to traditional power management. Using cloud computing applications, energy management techniques in smart grid can be evaluated within the cloud, instead of between the end-user’s devices. On the concern of communication and information management in smart grid (SG), cloud computing is used in different scenarios.

[10]

[11]

[12]

[13]

Owusu, F., & Pattinson, “ The current state of understanding of the energy efficiency of cloud computing”, IEEE 11th International Conference on Trust, Security and Privacy in Computing and Communications (TrustCom), pp. 1948-1952, June 2012. Huang, Q, Zhou, M., Zhang, Y., & Wu, Z. ” Exploiting cloud computing for power system analysis” IEEE International Conference on Power System Technology (POWERCON), pp. 1-6, October 2010. Kamali Gupta, and Vijay Kummar Katiyar "Survey of Adaptive and Dynamic Management of Cloud Datacenters", IJERA National Conference on Advances in Engineering and Technology (AET), pp-35–40, 29 March 2014. Rahul Bhoyar and Prof Nitin Chopde, “Cloud Computing: Service models, Types, Database and issues”, International Journal of Advanced Research in Computer Science and Software Engineering, pp.695-701, 3 March 2013. Laura Savu, “Cloud Computing Deployment models, delivery models, risks and research challenges ”. ”, IEEE International Conference on Computer and Management (CAMAN), pp. 1-4, 19-21May 2011. K.Divya, S.Jeyalatha, "Key Technologies in Cloud Computing," International Conference on Cloud Computing Technologies, Applications and Management(ICCCTAM), pp-196-199, December 2012. J. O. Petinrin and Mohamed Shaaban, “ Smart power grid : Technologies and Applications,” IEEE International Conference on Power and Energy (PEcon), pp-892-897, December 2012. Xi Fang and Satyajayant Misra, “Managing Smart Grid Information in the Cloud Opportunities, Models, and Applications” Network, IEEE, vol.26, Issue-4, pp.32-38, 23 July 2012. H.Kim, Y.J. Kim, K, Yang, and M.Thottan, “Cloud-based Demand Response for Smart Grid-Architecture and Distributed Algorithms, “in Proc. Of IEEE Intl.Conf. on SmatGridComm, pp.398-403, 2011. C.-T. Yang, W.-S. Chen, K.-L. Huang, J.-C. Liu, W.-H. Hsu, and C.-H. Hsu, “Implementation of Smart Power Management and Service System on Cloud Computing,” in Proc. of IEEE Intl. Conf. on UIC/ATC, pp. 924–929, 2012. T. Rajeev and S. Ashok, “A cloud computing approach for power management of micro grids,” in Proc. of IEEE Conf. on ISGT, pp. 49–52, 2011. H. Lv, F. Wang, A. Yan, and Y. Cheng, “Design of cloud data warehouse and its application in smart grid,” in Proc. of IEEE Intl. Conf. on ACAI, pp. 849–852, 2012. S. Rusitschka, K. Eger, and C. Gerdes, “Smart Grid Data Cloud: A Model for Utilizing Cloud Computing in the Smart Grid Domain,” in Proc. of IEEE Intl. Conf. SmartGridComm, pp.483–488, 2010.

Transmission Expansion Planning in Indian Context: A Review Raminder Kaur

Maneesh Kumar

Assistant Professor, Department of Electrical Engineering, P.E.C. University of Technology, Chandigarh–160012, India e-mail: [email protected]

M.E., Department of Electrical Engineering, P.E.C. University of Technology, Chandigarh–160012, India e-mail: [email protected]

Abstract—The power system scenario is continuously changing day by day may be because of change in load, presence of deregulated environment or may be because of other newly invented technologies, it is now recommended for a power system engineer to know all related advancements and should be capable of understanding deregulated environment. A power system transmission expansion planning includes many approaches; here we will take the long term expansion planning for the transmission system in Indian context. This paper is presented to see the present facilities available in India also the approaches for transmission expansion planning. Keywords: Transmission Expansion Planning(TEP), Long Term Transmission Expansion Planning (LTEP); Indian Power Systems, Deregulated System, Load, Central Electricity Authority (CEA)

I.

recommendations regarding decisions to be made today. The main objective of transmission planning is not to determine the shape of the future transmission network only but also to see all possible changes in planning due to different environmental prospective. Any long-term transmission plan will ever be able to accurately forecast the facilities that will materialize over a 20 year period. Rather, the goal of transmission expansion planning is to make the best possible recommendation about what to do in the present scenario. By considering the future options, their costs and likelihood as suggested above, good choices are enabled that tend to minimize future regret about past decisions. 1.

INTRODUCTION

The approach used for transmission expansion planning such as LTEP [1] is used over a period of 10 or more years. It includes approach towards optimal investments on new transmission lines that make up an economic and reliable electrical network. The main interest of transmission expansion planning extends to competitive frameworks also. Due to presence of competition available in this field and a number of projects under consideration, regulators and other stakeholders are required for examination of basic system wide needs. Today’s environment is more or less became deregulated and the existences of competition between different players are there. Hence study of this restructured and deregulated environment is also needed. The current deregulation environment often results in a mix of market competition in the generation and distribution sectors, with a centralized regulation for transmission[2].

II.

OBJECTIVE OF PLANNING

The scenario analysis is required in effective longterm planning, which develops alternate future based on the variation of major drivers–population growth, technology, regulatory policy, etc. From the transmission planner’s perspective, each such scenario develops a possible load and resource trajectory (i.e. timing of events and their geographical locations) for which a transmission expansion plan must be developed. By examining scenario probability, transmission planners can make informed

The objectives of a long term transmission plan are: a.

To meet expected future demands for delivery of energy and facilitate energy trade across the region.

b.

To Considers environmental factors to reduce impact of network expansion.

c.

To provides expansion in such a way that it will not be overbuilt and the scope of further expansion always be there.

d.

To provide a planning guidance for nearterm decision making for transmission System Assessment Planning which includes detailed evaluation of transmission facilities over a 10-year period. As distribution load forecasts are considered, it is possible that projections indicate that one or more reliability criteria would not be met at some date in the future. In such cases, remedial actions are developed and planned to assure the system continues to comply with reliability criteria. There are a number of possible actions that can address transmission system reliability criteria deficiencies:

1.

Additional transmission lines on the existing right-of-way (ROW) or new ROW;

2.

Increasing the capacity of existing transmission components by:


a.

Re-conductor of existing transmission line with higher capacity conductor;

b.

Installation transformer.

of

parallel

transmission

3.

Upgrade of existing facility to higher voltage;

4.

Installation of transmission capacitor banks in various transmission as well as distribution stations and/or,

5.

1.

Combinations of the above.

It is possible that the Interconnection of New Generation Resources Reliability criteria can be met in some cases for the expansion planning by the Interconnection of new generation resources within the system or by interconnections to new or existing generation resources outside the system. New generation resources are basically not only a source of additional real power but they are also a source of reactive power, all of which help bring the system into compliance with reliability criteria. Resources closer to load will provide greater reactive support than those further away. At some point, the interconnection of new generation resources is needed to meet reliability and supply requirements.

System Reliability.



A robust competitive market.



Improving transmission system efficiency.







Future demand for electricity must be anticipated, also the generation capacity and appropriate reserves required to meet the forecast load must be considered.

Forecasting of load on the interconnected electric system, that also includes export of electricity,



Anticipation of generation capacity.



Identification of timing and location of future generation additions.



Finalization of transmission facilities required to meet the forecast load, imports and exports.



Establishment of transmission facilities required to provide for the efficient and reliable access to jurisdictions, and



Other matters related to the items described in sub clauses (i) to (v) that the Central Electricity Regulating Authority has to: periodically as required[3].

b. Make

the transmission system plan, including the assumptions and supporting data on which the plan is based, and the updates made to the plan, available to the public, and file copies of them with the Commission and the Minister for information.

To accomplish Transmission planning, the following forecasting needs[14]: 



a. Update the transmission system plan

III. FORECASTING OF FUTURE NEEDS [7] 

The Preparation and the maintenance of a transmission system plan for at least the next 20 years shall have the following steps [5]:

IV. FACTORS AFFECTING LTEP The following are the various factors that will affect the Plan: 

Changes in reliability requirements.



Changes in economic load forecasts.

Assumptions about future load growth must be considered, the timing and location of future generation additions and other related assumptions.



Impact of demand side management programs.



Impacts from the State’s Energy regulating programs.

An assessment of the transmission facilities must be prepare which is required to provide the efficient and reliable access to jurisdictions outside the country and



Other state and national policy programs such as the Regional Greenhouse Gas Initiative.



Deregulation in generation and transmission[9].



Decisions under the ISO’s Comprehensive Reliability Planning Process.



Political factors.

If the ISO considers it necessary to do so, make an assessment of the contribution of a proposed transmission facility to any of the following:



Improving transmission system.



Improving operational flexibility of the system.



Maintaining options for long term development of the transmission system.

V. ENVIRONMENTAL FACTORS IN LONG-TERM PLANNING To obtain a transmission plan environmental constraints must be considered. To ensure that it’s

Transmission Expansion Planning in Indian Context: A Review  73

planning studies pay adequate attention to land use, wildlife, water, and other factors. Wildlife, is particularly sensitive to the impacts of electricity transmission lines. Transmission modeling tools to be proposed that accommodate both qualitative and quantitative environmental data (wildlife, land use, water, etc.). The Proposed tools should incorporate environmental data directly from state agencies, and may include both quantitative and qualitative data, as well as provide mapping and other graphic data to assist data users in making routing decisions during study case development. The proposed tools must also be flexible to consider new data inputs, such as environmental geographic information system data analysis or changing policy requirements that may impact carbon emissions, location, costs, and other variables important to future use of the long-term planning tools and policy analysis. Incorporating environmental data into transmission planning tools is a relatively new concept and seeks innovative approaches to accommodating this capability.

VI. LIMITATIONS Transmission utilities during its analysis to obtain and identify all concerns that may require system upgrades, however, some concerns may not have been identified due to insufficient information, unforeseen events, new requirements or the emergence of new information. From time to time, utilities must check improvements in its system to replace obsolete equipment, make repairs; relocate a piece of equipment, or otherwise carry out its obligations to maintain a reliable grid. Sometimes such activities require significant changes, such as the current work to replace obsolete equipment and line rebuilds to replace aging equipment or maintain acceptable ground clearances. All issues which relates to planning and development of Transmission System in India are dealt in the Power System Wing of CEA. This includes evolving long term and short term transmission plans. The network expansion plans are optimized based on network simulation studies and techno-economic analysis [6]. It also involves formulation of specific schemes, evolving a phased implementation plan in consultation with the Central and State transmission utilities and assistance in the process of investment approval for the Central sector schemes, issues pertaining to development of National Power Grid in the country. Transmission planning studies are being conducted to identify evacuation system from generation projects and to strengthen the transmission system in various regions. The studies for long-term perspective plans are also being carried out on All India basis for establishing inter regional connectivity aimed towards formation of the National Power System. The National Power System is beingevolved to facilitate free flow of power across regional boundaries, to meet the short fall of deficit regions from a surplus region as well as for

evacuation of power from project(s) located in one region to the beneficiaries located in other region(s).

VII. TOOLS AND METHODOLOGIES REQUIRED FOR PLANNING The classic tools which are being used in transmission system planning are power flow and dynamic stability analysis. These analytic tools are well developed and broadly applied. They are used to evaluate the performance of proposed additions to the transmission system against reliability criteria for system performance.[8] They result in transmission system ratings that allow system operators to maintain system reliability while serving the energy needs of the system users because of change in load demands. Transmission system can be assessed using a variety of system modeling and simulation tools to measure the transmission system’s capabilities against design criteria. This is done for present and planned configurations at present and future load levels, respectively. The simulations techniques are validated using real-time measurements that are made under normal and contingency conditions whenever possible. Assessments are made in the following areas, using standardized software packages to study the system’s performance[10]: a.

Thermal.

b.

Voltage.

c.

Short Circuit.

d.

Under-frequency Load Shedding.

e.

Extreme Contingencies.

A. Thermal Load flow studies are the primary method used by Transmission Planning to assess the performance of the transmission system under normal and contingency conditions. The software’s used for these studies are MATLAB, PSCAD, Mipower and PSS/ E. These are the leading software packages for bulk transmission system load flow studies. The load flow levels established by the studies are measured against the thermal ratings of transmission facilities. Transmission equipment including lines and transformer banks are assigned with thermal ratings for normal operation, long-time emergency operation (LTE), and short-time emergency operation (STE). Load flow studies are conducted to simulate normal operation under peak forecast loads. No transmission facilities should exceed their normal ratings at this operating condition[12]. During single contingency conditions, no facilities should exceed their LTE ratings. Also following the various


contingency conditions transmission system must exhibit the capability to be returned tooperation within normal thermal limits following the worst case single contingency within the time frame specified in the rules.

B. Voltage Voltages throughout the transmission system are checked using the same load flow studies that are used tomake the thermal assessments described in the section above. The focus, however, shifts from the delivery of real power, measured in MW, to voltage support and control provided by reactive power, measured in MVAR.

In the N‐1‐1 scenario, planners assume one element is out of service followed by another event that occurs after a certain period. After the first contingency operators have to make adjustments to the system in preparation for the next potential event, such as switching in or out certain system elements, resetting inter‐regional tie flows where that ability exists, and turning on peaking generators. In each scenario, if the software used to simulate the electric grid system shows the system cannot maintain within acceptable levels of power flow and voltage, a solution is required to resolve the reliability concern[13].

VIII.

C. Short Circuit Short circuit studies are conducted to assess the following: 1.

2.

The ability of circuit breakers on the transmission system to interrupt fault currents under abnormal conditions; and The ability of all equipment on the transmission system, including but not limited to circuit breakers, nodal buses, disconnect switches, and structural supports to withstand the mechanical forces associated with the fault currents.

Momentary forces generated within the first one-half cycle following the commencement of a fault typically present the highest mechanical stresses[16].

D. Under-frequency Load Shedding The purpose of Under Frequency Load Shedding (UFLS) is to balance generation and load when an event causes a significant drop in frequency of an interconnection hence, Under-frequency relays are installed at various points throughout the system to provide protection against widespread system disturbances.

E. Extreme Contingencies As required by the standards, system planners measure system performance under three progressively more stressed conditions to determine whether the system will remain within mandatory performance criteria under various operating conditions. Planners analyze the system with: 1.

All facilities in service (no contingencies or N‐0).

2.

A single element out of contingency or N‐1).

3.

Multiple elements out of service (multiple, due to a single contingency or a sequence of contingencies, i.e., or N‐1‐1).

service

TRANSMISSION SYSTEM PERFORMANCE CRITERIA

The performance of the transmission system may include analyses, such as: 1.

Stability assessment of system, the analysis of system dynamic performance as a result of sudden system condition changes including those caused by a contingency;

2.

Steady state assessment of system, the analysis of power flows pre and post contingencies when the system has returned to synchronism;

3.

Voltage assessment of system, the analysis of reactive power sources/sinks to control the voltage[11];

4.

Fault current assessment in system, the analysis of the capability of electrical devices to physically withstand and interrupt short-circuit currents present in the system; and

5.

Power-quality assessment of system, the analysis of current and voltage waveforms for distortion.

IX. CHALLENGES PRESENT IN TRANSMISSION SECTOR IN INDIA [4] Its worthy to say that to meet the growing power demand of various regions, power transfer capacity of the grid is being enhanced continuously. This expansion poses few challenges that need to be met through the planning and adoption of new technologies[15]. 1.

Following are some of the challenges: a.

Right Of Way (ROW)

b.

Flexibility in Line Loading and Regulation of Power

c.

Improvement of Operational Efficiency

(single

2.

Following are the measures being implemented to meet above challenges:

Transmission Expansion Planning in Indian Context: A Review  75

a.

b.

Increase in transmission voltage: Power density of transmission system (MW per meter ROW) is being enhanced by increasing the voltage levels. It is 3 MW/m for 132kV and 45 MW/m for 765kV. Transmission voltage upto 765kv level are already in operation. A ±800 kV, 6000 MW HVDC system as a part of evacuation of bulk power from North Eastern Region (NER) to Northern Region (NR) over a distance of around 2000 km is under implementation. In addition, increasing the AC voltage level at 1200kV level has been planned. Research work for 1000kV HVDC system has also been commenced. Upgradation of transmission line: Upgradation of 220kV D/C KishenpurKishtwar line in J&K to 400 kV S/c, which was first time in India, has resulted in increase of power transfer capacity of the existing transmission system with marginal increase in ROW (from 35m to 37m).

c.

Upgradation of HVDC terminal: Upgradation of Talcher(ER)–Kolar(SR) 500kV HVDC terminal from 2000MW to 2500MW has been achieved seamlessly without changing of any equipment. That has been achieved with enhanced cooling of transformer and smoothing reactor with meager cost.

d.

High capacity 400kV multi-circuit/ bundle conductor lines: POWERGRID has designed & developed multi circuit towers (4 Circuits on one tower with twin conductors) in-house and the same are implemented in many transmission systems, which are passing through forest and ROW congested areas e.g. Kudankulam and RAPP-C transmission system.

e.

High surge impedance loading (HSIL) line: In order to increase the loadability of lines, development of HSIL technology is gaining momentum. POWERGRIDis building up one HSIL line viz. 400kV Meerut–Kaithal D/c where SIL is about 750 MW as against nominal 650MW for a normal quad bundle conductor line.

f.

Compact towers: Compact towers like delta configuration, narrow based tower etc. reduce the space occupied by the tower base are being used. First 765kV Sipat–Seoni 2xS/c line with delta configuration tower is under operation. Further, 400kV Pole structure is also being used in

highpopulationdensity areas. Pole type structures with about 1.85m base width as against 12-15m base width of a conventional tower were used in transmission line approaching Maharani Bagh, Delhi substation to address Right-of-way problem in densely populated urban area. g.

Increase in current: High Temperature Low Sag (HTLS) conductor line:High temperature endurance conductor to increase the current rating are in use for select transmission corridors and urban/metro areas. POWERGRID has already implemented twin INVAR conductor line for LlLO portion (15kms stretch) of 400kV Dadri-Ballabgarh quad conductor line at Maharanibagh substation. Further, the Siliguri–Purnea, twin Moose conductor line is being re-conductored with high temperature low sag (HTLS) conductor.

h.

Reduction in land for substation: With scarce land availability there is a growing need for reduction of land use for setting up of transmission systems, particularly in Metros, hilly and other urban areas. Gas Insulated Substations (GIS), requires less space (about 70% reduction) i.e. 8-10 acres as compared to conventional substation which generally requires 30-40 acres area.

i.

Regulation in power flow/ FACTS devices: With electricity market opening up further, more and more need has been felt to utilize the existing assets to the fullest extent as well as regulate the power. This could be possible through use of power electronics in electricity network.

j.

Improvement of operational efficiency by condition based monitoring of the system [4]: POWERGRID has adopted many state of the art condition monitoring & diagnostic techniques such as DGA, FRA, PDC, RVM etc. for transformers, DCRM for CBs, Third Harmonic Resistive current measurement for Surge Arrestors etc. to improve Reliability, Availability & Life Extension. Further, online monitoring systems for transformers have been implemented to detect faults at incipient stage and provide alarms in advance in case of fault in the transformers.

k.

Preventive maintenance: Preventive Stateof-the-art maintenance techniques for various equipment in our power system applied include on-line monitoring of


various components of transformers and reactors, Circuit Breakers, Instrument transformers, lightening arrester etc. l.

1200kV Test station: In order to increase the power density of the corridor, development of 1200kV AC system as next higher AC voltage level has been decided. However, 1200kV AC technology is relatively a new one in the world. Therefore, to develop this technology indigenously, a unique effort has been made by POWERGRID through a collaborative research between POWERGRID and Indian manufacturers to establish a 1200kV UHVAC Test Station.

X. CONCLUSION In this paper the objectives, needs and also limitations of Long Term Transmission Expansion Planning are discussed. Assessment of load forecasting, generation growth, socio-economical, Political constraints and environmental impacts required for Transmission Expansion Planning are explained. Tools and methodologies required for transmission planning and transmission system performance criteria are described. Existing transmission facilities available in India are presented here and also suggested different LTEP methodologies incorporates for Indian Power System.

REFERENCES [1]

[2]

G. Latorre, R.D. Cruz, and J.M. Arezia, “Classification of publications and models on Transmission Expansion Planning” presented at IEEE PES transmission and Distribution Conf, Brazil, Mar. 2002. M. Oloomi Buygi, H.M. Shanchei “ Transmission Expansion Planning Approaches In Restructured power systems ” IEEE Bologna Power Tech Conference, ISSN 1004-2334, Italy

[][]j[]

[3]

[4] [5]

[6]

[7]

[8]

[9]

[10]

[11]

[12] [13]

[14] [15]

[16]

R.E. Clayton, and R. Mukerji, “System planning tools for the competitive market,” IEEE Trans. Computer Application in Power, Vol. 9, No. 3, pp. 1150-1155, Jul. 1996. Manual on transmission planning criteria by central electricity authority New Delhi, january 2013 Rajeev Chaturvedi 1, Kankar Bhattacharya*, Jyoti Parik “Transmission planning for Indian power grid: A mixedinteger programming approach” Published by Elsevier Science Ltd. All rights reserved.Vol.14. pp.59-30, june2013 R. Baldick, and E. Kahn, “Transmission planning issues in a competitive economic environment,” IEEE Trans. PWRS, Vol. 8, No. 4, pp. 1497-1503,Nov. 1993. Lee, C.W.; Ng, S.K.K.; Zhong, J.; Wu, F.F, “Transmission Expansion Planning From Past to Future”, Power Systems Conference and Exposition, PSCE '06, IEEE PES, pages: 257–265, July 2006 De la Torre, S.; Conejo, A.J.; Contreras, J, “Transmission Expansion Planning in Electricity Markets”, IEEE Transactions on Power Systems, Vol: 23,No:1, pages: 1238-1248, Feb. 2008. Wu, F.F.; Fenglei Zheng, Fushuan Wen, “Transmission planning in restructured electric power systems”, IEEE Power Tech, Pages 142005, July 2013.e\ “Long term transmissionexpansion planning for Indian power : A review” By Mr.G.Srinivasulu Associate Professor, Dept. of EEE, Narayana Engineering College, Nellore, AP, India IEE, vol 23, pp 3023-3029 june 2012. Hadush S.Y. ; R. Belmans “Offshore wind Power Generation and Transmission Tariff design options” Deptt. Of EE University of leuven, Kasteel Arenberg 10,3001 Leuven,Belgium vol. 24. June2013. Zhao Xu, Zhao Yang Dong, “ Multi-objective Transmission Planning” IEEE Transaction vol. 32 pp1322-1326, Aug 2009. R.A Jabr, member IEEE “Robust Transmission Network Expansion planning with Uncertain Renewable Generation and Load” IEEE Transaction, vol. 45, pp 202-208, june 2008 Z.Xu, Z.Y. Dong “Transmission planning in a deregulated environment”, IEE pro.-Gener. Transm., Vol.153. No. 3, May 2006 Bharti Dewani, Dr. M.B Daigavane, Dr. A.S. Zadgaonkar, “ A Review of various Computational intelligence techniques for transmission network expansion planning ”, IEEE Transaction, vol50. Pp 1010-10152012,. Seyed Mohammad Ali Hossein, “ Transmission Network Expansion Planning in the Competitive Environment, A Reliability Based Approach IEEE Transaction, vol3, pp. 2132-2139.July 2011

High Frequency Modelling of Distribution Transformer Rohit Gupta

Mukesh Pathak

Assistant Professor, EE, HSET, Swami Rama Himalayan University Dehradun, India e-mail: [email protected]

Associate Professor, EE, IIT Roorkee, India e-mail: [email protected]

Dr. Ganesh Kumbhar Assistant Professor, EE, IIT Roorkee, India Abstract—It is very important to develop an accurate high frequency model of a distribution transformer. It helps to improve the high frequency characteristics of the distribution transformer at designing stage. This work presents a simple procedure to obtain the high frequency model of a distribution transformer. A two-port network model of the distribution transformer has been developed using Z-parameters. The Z-parameters are very easy to be evaluated as only open circuit test is required for that. The high frequency equivalent circuit model of the distribution transformer has been developed using MATLAB Fast Fourier Transformations as a tool. Keywords: high Frequency; model; distribution transformer; two-port network; z-parameter; open circuit test; fast Fourier transformations.

I.

arrangement. A switching transient has been applied with the help of a contactor (40A), relay (12V, 2A) and timer (1-3 sec.) arrangement to the transformer.A Digital Storage Oscilloscope (4 channel, 100 MHz) has been used to record input and output voltage and current signals in time domain.

INTRODUCTION

Distribution transformers are designed to function at 50 Hz. But when the windings are applied with high frequency voltage transients, then the behavior of windings is very different, which is needed to be considered at the designing stage of the transformer. Hence, modeling the distribution transformer for high frequency is very important. The investigator has implemented the Two-Port Network approach to develop a high frequency model of a distribution transformer from experimentally obtained results.

Fig. 1: Block Diagram for Experimental Measurements

The experimental measurements have been carried out in the following two steps [11]: Step I: The LV side of the transformer has been opened and a dc switching transient of 20V has been applied on the HV side then the primary voltage (V1), secondary voltage (V2) and primary current (I1) traces have been captured through channels CH1, CH2 and CH3 of the Digital Storage Oscilloscope respectively.

To evaluate the Z-parameters an open circuit test has been conducted on a transformer experimentally. The experimental measurements have been carried out by the investigator on a practical Single Phase Transformer of 1KVA at the Electrical Machines Laboratory, Indian Institute of Technology (IIT), Roorkee, India.

Step II: The HV side of the transformer has been opened and a dc switching transient of 10V has been applied on the LV side , then the primary voltage (V1), secondary voltage (V2) and secondary current (I2) traces have been captured through channels CH1, CH2 and CH3 of the Digital Storage Oscilloscope respectively.

As shown in Fig.1, a 1KVA, 230V/115V, Single phase, 50Hz, 4.5A/9A transformer has been given a d.c supply of 20V on HV side (with LV side opened) and 10V on LV side (with HV side opened) from a d.c.generator (5KW, 230V, 21.8A, 1440 RPM) and rheostat

The time domain signals have been obtained as WFM (Wave Form) files and their corresponding Microsoft excel data sheets as CSV(Comma Separated Values) files with 8195 values. The WFM files obtained for step I and step II have been shown in Fig. 2 (a) and (b) respectively.

II.

EXPERIMENTAL MEASUREMENTS


After obtaining thee graphs frrom experim mental measurements, our next step has beeen to developp the model of the transformer. t

(a)

main using FF FT in MATLA AB [14]. Thee to frrequency dom ampllitude and phhase graphs off step I and step s II signalss with respect to freequency have been plotted and shown inn Fig. 4, 5, 6 and 7, 8, 9 respectivvely.

(b)

Fig. 2(a): Thee Primary Voltagge (V1), Secondarry Voltage (V2) and a Primary Currentt (I1) from Step I of Experimental Measurements (bb)The Primary Voltagee (V1), Secondaryy Voltage (V2) And A Secondary Cuurrent (I2) from Step II of Experimental E Meaasurements

III. MODELING The voltage and current signnals obtainedd as experimental measuremennts can be useed to developp the high frequenccy model of a distributionn transformer.. The below given flowchart inddicates the allgorithm to reealize the model froom experimenttally obtainedd results.

Fig g. 4: FFT of the Prrimary Voltage (V V1) from Step I of o Experimental Measuurements. (a) Am mplitude (b) Phasee

Fig. 5: FFT of the Seccondary Voltage (V2) from Step I of Experimental Measuurements. (a) Am mplitude (b) Phasee

Fig. 3: Flow Chart for Two Port Networrk Modeling

The tim me domain siignals can be b converted into frequency doomain using Fast Fourierr Transformattions, then the Z-pparameters caan be found as a functioon of frequency. Thhe T-parameteers can be obttained in frequuency domain from m Z-parameeters. Then high frequuency equivalent cirrcuit parameteers can be calcculated by loccating the resonant frequencies from the frequency f doomain p graphs of T- parameters.

A Evaluatiion of Fast Fourier A. F Transformations (FFT The timee domain signaals obtained inn step I and sttep II of the experim mental measurements have been convertted in

Fig g. 6: FFT of the Primary P Current (I1) from Step I off Experimental Measuurements. (a) Am mplitude (b) Phasee

High Frequen ncy Modelling off Distribution Tra ansformer  79 9

B. Evaluation E o Z–Parameeters of The Z- param meters can bee obtained as a function off frequ uency with thee help of folloowing formulaae [18] :-

Fig. 7: FFT of the Primary Volttage (V1) from Steep II of Experimeental Measurements. (a) Amplitude (b) Phase

As A V1 ,V2 , I1 from step I aand V1 ,V2 , I2 from step III havee been obtaineed as frequenccy domain sig gnals, Z11, Z12, Z21 and a Z22 can also a be obtainned in the fo orm of graphss show wing the magnnitudes and pphases of Z11, Z12, Z21 andd Z22 with w respect to t frequency as shown in Figs.10,11,122 and 13 1 respectivelly.

Fig. 8: FFT of thhe Secondary Voltage (V2) from Step S II of Experim mental Measurements. (a) Amplitude (b) Phase

Fig. 10: The Z-Parameter Z (Z11) (a) Magnitude in i Ohms (b) Angle in R Radians

Fig. 9: FFT of the Secondry Currrent (I2) from Step II of Experimeental Measurements Amplitude (b) Phase

Fig. 11: The Z-Parameter Z (Z122) (a) Magnitude in i Ohms (b) Angle in R Radians


By using these relations we can get the frequency domain graphs of Za, Zb and Zc as shown in Figs.15, 16 and 17.

Fig. 12. The Z-Parameter (Z21) (a) Magnitude in Ohms (b) Angle in radians

Fig. 15: The T-Parameter (Za) (a) Magnitude in Ohms (b) Angle in radians

Fig. 13: The Z-Parameter (Z22) (a) Magnitude in Ohms (b) Angle in Radians

C. Evaluation of T-Parameters For a T-network as shown below:

Fig. 16: The T-Parameter (Zb) (a) Magnitude in Ohms (b) Angle in Radians

Fig. 14: The T- Network

The relations for T-Parameters Z-Parameters are given below:

in

terms

of

Za = Z11 - Z12

(5)

Zb = Z22 - Z12

(6)

Zc = Z12

(7)

Fig. 17: T-Parameter (Zc) (a) Magnitude in Ohms (b) Angle in Radians

ncy Modelling off Distribution Tra ansformer  81 1 High Frequen

D. Calculattion of Equivvalent Circuiit Parameterrs From thee frequency domain d graphss of Za, Zb annd Zc minimum andd maximum peaks p can be identified. As A we know that im mpedance is minimum m correesponding to series s resonance and a maximum m corresponnding to paarallel resonance. Soo, the series annd parallel resonant frequeencies and the corresponding imppendence valuues can be reaad out from the grapph [13].

The Table 1 gives g the maxiimum and min nimum valuess of Za, Zb, Zc and thhe correspondding frequency y values TABLE 1: MAXIMUM AND MINIM MUM VALUES OF ZA, ZB, ZC

i.e.

Za Zb

fc

Zc

While W calculaating C , the L value can bee evaluated byy takin ng |Z| as valuue at high frequency i.e 68 84.9Hz and R can be b taken as thee minimum vaalue. While W calculaating L, the C value can bee evaluated byy takin ng |Y| as valuue at high freequency i.e 68 84.9Hz and R can be b taken as the t maximum m value. Tablee 2 shows thee calcu ulated elementt values for thhe transformerr.

Frequencyy

TABLE 2: ELEMENT VALUEES FOR TRANSFOR RMER

C in eqn.

L

So the parameetric values off the transform mer have beenn obtaiined for high frequency f equuivalent circuiit model From m the high frequenncy equivaleent circuit model m of thee transsformer, we can c develop thhe transfer fu unction of thee transsformer. By usingg the above givven proceduree, we can calcculate the parameters of the higgh frequency equivalent circuit model of the transformer t [119] as shown in Fig. 18.

We W can draw w the equivaleent circuit in s-domain byy replaacing L by sL and C by 1/sC C . Then we get g T-model off the trransformer in s-domain as sshown in Fig. 19.

Fig. 18: The Higgh Frequency Equuivalent Circuit Model M of a Transfformer

Fig. 19: The T-model of the T Transformer in S--domain


Then the Transfer Funnction can be calculated c as:

[3]

[4]

[5]

IV. CONCLUSION O

[6] [7]

This worrk presents a simple s proceddure to obtainn high frequency moodel of a disttribution transsformer. The work can be concluuded as:

[8]





The open circuit test has been conducted on a distrribution transsformer to get voltage and curreent signals in time domain. The time domain voltage v and cuurrent signals have beenn converted innto frequency domain usingg Fast Fourrier Transform mations (FFT).

[9]

[10]



The frequency domain volttage and cuurrent signaals have been b used to evaluate the Z- paarameters grapphs in frequenncy domain.

[11]



The Z- parameterrs graphs in frequency doomain havee been used to evaluate the t T- param meters graphs in frequenccy domain.

[12]



The T- parameterrs graphs in frequency doomain t evaluate thhe high frequuency havee been used to equivvalent circuitt parameters using u maximaa and miniima of the graaphs.

[13]



Finaally the highh frequency equivalent circuit moddel of the disstribution trannsformer has been deveeloped.

[14]

[15]

V. FUTURE U SCOPE E This worrk can furtheer be extendeed as a simullation work. The frequency f anaalysis of the transfer funnction model can bee done to obtaiin the frequenncy response of o the distribution trransformer. This T frequencyy response is very helpful while designing thee distribution transformers. t

[16]

[17]

[18]

REFE ERENCES [1]

[2]

T. Noda, H. H Nakamoto, S.Y Yokoyama, “Accuurate Modeling off CoreType Distrribution Transfoormers for Elecctromagnetic Traansient Studies”, IE EEE Transactionss on Power Delivvery, Vol. 17, Noo. 4, pp 969-976, October, O 2002. N.A. Sabiiha, M. Lehtoonen, “Experimeental Verificatioon of Distributionn Transformer Model under Lightning Strrokes”, IEEE/PES, Power Systems Conference and Expositionpp 1--6, 1518 March, 2009. 2

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E. E Agheb, A. A. S. Akmal, S. Essmaiilzadeh, E. Hashemi H , “EMTP P Modeling M of Air-Cored A Transsformer Winding gs under HighFrequency F Transsient”, Internationnal Journal of Pllasma and Fusionn Research R Series, Vol. 8, pp 1487-1490, October, 20 009. W. W C. Black, N. E. Badr, “Highh-Frequency Chaaracterization andd Modeling M of Distribution D Traansformers”, IEE EE Internationaal Symposium on Power P Line Com mmunications and d its Applicationss, ISPLC, I pp 18-21, 28-31 March, 2010. E. E Agheb, S. Esm maiilzadeh, K. N Niayesh, J. Jadidiian, E. Hashemi , “Transfer “ Functioon based Modelinng of the Air-Co ored Transformerss for Very Fast Transient Oveervoltage Studies”, Internationaal Journal J of ACTA A PHYSICA POL LONICA A, Vol. 115, No. 6, pp p 1141-1143, April, A 2009. T. T H. Chen, Q. Y. Y Pan, N. C. Yaang, “Modeling and a Analysis of a Single-Phase Distribution D Trannsformer with Midtap on thee Secondary Side””, IEEE Transactiions on Power Delivery, D Vol. 25, No. N 3, pp 1580-1588, July, 2010. E. E Bjerkan, H. K. K Hoidalen, “Hiigh frequency FE EM-based Powerr Transformer T Moodeling: Investigaation of Internall Stresses due too Network N Initiateed Over-Voltagees”, Internationall Conference onn Power P Systems Transients, T Montrreal, Canada, 19– –23 June, 2005. M. M H. Hosseini, M. Vakilian, G. B. Gharehpetian, “Comparison of Transformer T Dettailed Models foor Fast and Verry Fast Transiennt Studies”, IEEE Transaction T on P Power Delivery, Vol. 23, No. 2, 2 pp p 733–741, Aprril, 2008. P. P G. Blanken, “A A Lumped Windding Model for usse in Transformerr Models M for Cirrcuit Simulation””, IEEE Transaaction on Powerr Electronics, E Vol. 16, No. 3, pp 445 - 460, May, 200 01. S. Okabe, M. Kooutou, T. Teranishhi, S. Takeda, T.. Saida, “A HighFrequency F Modeel of an Oil-Imm mersed Transform mer, and its use inn Lightning L Surgee Analysis”, Trransactions of the Institute of Electrical E Enginneers of Japan, Vol. 134, No o. 1, pp 28-35, January, J 2001. Y. Y Shibuya, S. Fujita, “High F Frequency Modeel and Transiennt Response R of Transformer W Windings”, Traansmission andd Distribution D Connference and Exhhibition Asia Paacific. IEEE/PES, Vol. V 3, pp 1839 – 1844, 6-10 Octoober, 2002. Y. Y Wang, W. Chhen, C. Wang, L. Du, J. Hu, “A Hybrid Model off Transformer T Winndings for Very F Fast Transient Analysis A Based onn Quasi-stationary Q Electromagneticc Fields”, Interrnational Journaal of o Electric Pow wer Components and Systems, Vol. V 36, No. 5, pp p 540 – 554, Maay, 2008. N. N A. Sabiha, M. Lehtonen, ““Lightning-Inducced Overvoltagess Transmitted T over Distribution T Transformer with h MV Spark-Gapp Operation-Part O I High-Frequenncy Transformerr Model”, IEEE I: E Transactions T on Power Deliveryy, Vol. 25, No. 4, 4 pp 2472-24800, October, O 2010. Y. Y Shibuya, S. Fujita, F “ A High Frequency Modeel of Transformerr Winding”, W Transsactions of the Innstitute of Electriical Engineers of Japan, J Vol. 146, No. N 3, pp 8–16, F February, 2004. C. C de Salles, M. M L. B. Marttinez, “ Model of Distributionn Transformers T Wiinding for Lightnning”, IEEE Confference on Powerr Tech, T Lausanne, pp 2047-2052, Juuly, 2007. M. M Popov, L. Vaan der Sluis, R. P P. P. Smeets, “Ev valuation of Surgee Transferred T Overrvoltages”, Internnational Journal on o Electric Powerr System Researchh, Vol. 78, No. 3, pp 441–449, Marrch, 2008. A. A Borghetti, A. Morched, F. Nappolitano, C. A. Nu ucci, M. Paolonee, “Lightning-Induc “ ced Overvoltagess Transferred thro ough Distributionn Power P Transform mers”, IEEE Trransactions on Power Deliveryy, Vol. V 24, No. 1, ppp 360–372, Januaary, 2009. C. C K. Alexandeer, M. N. O. Saadiku, Fundamentals of Electricc Circuits, C 3rd edition, New York: M McGraw-Hill, 2007. Design D Soft Co., Internet Course oon Circuit Theory y using Tina, AC circuits, c Resonannt Circuits. 2008. http://www.tina.c h com/course/28ressonant/ resonant.h htm.

Modeling and Control of Micro-Grid Under Grid Connected and Disconnected Mode Manoj Chhimpa

S. Chatterji

Government, Engineering College, Bikaner e-mail: [email protected]

National Institute of Technical Teachers Training and Research, Chandigarh

Lini Mathew National Institute of Technical Teachers Training and Research, Chandigarh Abstract—This paper describes connected mode and disconnected mode of distribution subsystem and formation of a micro-grid. In this micro-grid is composed of a two distributed generations (DG).One is a diesel-generator and second is two parallel connected inverter interfaced voltage source with voltage regulator. The two parallel connected inverter with voltage regulator is independent of real and reactive power control to minimize disconnected transients and maintain voltage stability and angle stability. The simulation of study system is performed with the help of MATLAB/SIMULINK software tool. This paper concludes that presence of an electronically-interfaced distributed energy resource unit makes the concept of micro-grid a technically viable option. Keywords: Distributed generation, Grid Connected, Grid Disconnected.

I.

INTRODUCTION

Now a day the energy shortage, deterioration of ecological environment and global warming are problems of our society. People have no choice but to develop distributed generation (DG), which is clean and renewable. Distributed generation contains hydraulic power, wind power, solar power and so on. DGs play a great role in energy conservation, environmental protection, investment, power safety and so on. However, compared with the traditional way, capacity of DG is small and power output is not stable. Distributed generation (DG) has been developing rapidly. But the direct connection of distributed generation to distribution system brings many new challenges, such as harmonics, voltage stability, relay protection, distribution system management and so on [1–4]. The study of DG has become one of electric power scientific research emphases [5]. Therefore, micro-grid (MG) is proposed to handle these problems. MG is envisioned as clusters of distributed generations, storage, and loads that are operated as single controllable systems. A micro-grid is

formed when an electrical region capable of autonomous operation is islanded from the remainder of the grid; e.g., a distribution substation along with its feeders that service DG units and local loads. A Micro Grid is defined as an independent Low Voltage (LV) or Medium Voltage (MV) distribution network comprising various Distributed Generations (DGs), Distributed Energy Storages (DESs), and controllable loads. It is a small-scale power supply network that is designed to provide power for a small community. It enables local power generation for local loads. It represents an entirely new approach to integrate distributed generations into utility distribution systems [6]. However, the problem of stability of micro-grid has been attracting more and more attentions, and it is necessary to mention that analysis of behaviors of distribution systems during transients is especially difficult, since DGs might have quite different dynamics [7]. Therefore, the transient stability of the micro-grid has to be deliberately investigated. The inverters in electric power system bring some problems. Firstly how the inverters (PQ control and VF control mode) sustain the voltage and frequency of the system, secondly how the inverters behave when fault occurs in the system. The inverters used in Micro grid are often PWM (Pulse Width Modulation control) controlled, for PWM control mode has some advantages such as lower Harmonic and flexible control.

II.

SYSTEM CONFIGURATION

Fig. 1 shows a single-line diagram of the system used to investigate typical micro-grid operational scenarios. The basic system configuration and parameters were extracted from the benchmark system of IEEE Standard 399–1997 [1], with some modifications to allow for autonomous micro-grid operation. The system is consisting of a 13.8-kVthree-feeder distribution subsystem which is connected to a large network through a 69-kV radial line.


Fig. 1: Single-Line Diagram of Micro-Grid System

The 13.8-kV distribution substation is equipped with a three-phase 1.5 MVAr, fixed shunt-capacitor bank. The 13.8-Kv substation bus bar is radially connected to the main grid through the substation transformer and a 69-kV

line. The network at the end of the 69-kV line is represented by a 69-kV, 1000-MVA short-circuit capacity bus. A combination of five loads is supplied through three radial feeders of the sub system.

Modeling and Control of Micro-Grid under Grid Connected and Disconnected Mode  85

G1……G6

Vabc(pu)Vabc(pu)

Pulse Uref

1/Z

M Vd_ref(pu)

Discrete PWM Generator1

1 Voltage Regulator 1

Fig. 2: Schematic Block Diagram of Generation of Gate Pulse

Loads L1 to L3 are composed oflinear RL loads. Loads L4 to L5 are the resistiveload. The system also includes two DG units, i.e., DER1 (5 MVA) and DER2 (150KVA) on feeders F1 and F3 respectively.DG1 is a synchronous rotating machine equipped with excitation and governor control systems. It represents a diesel-generator. DER2 utilizes a voltage-sourced converter (VSC) as the interface medium between its source and the power system. It represents a two parallel interfaced source with voltageregulator to control the gatepulses of inverter. DER2 also represents a constant source with adequate capacity to meet the real/ reactive power demand. TABLE 1: DISTRIBUTED ENERGY RESOURCE SPECIFICATION DER 1 Specification Sb= 5MVA, Vb= 13.8KV Xd

Ra

0.0036 (pu) 1.56 (pu)

Xq

0.052 (pu) 1.06 (pu)

Xd’ Xd’’ Td’ Td’’

0.296 (pu) 0.177 (pu) 3.7 (pu) 0.05 (pu)

Xq’ Xq’’ Tq0’’ H

0.85 (pu) 0.177 (pu) 0.05 (pu) 1.07 (pu)

Inverter Rated Voltage Rated Power

Xl

Vref(pu)

IV. CONTROL OF INVERTER INTERFACED SOURCE A. Voltage Regulator The Voltage Regulator is used to control voltage and frequency of micro grid by controlling gate firing pulses. This voltage regulator gives the input to discrete PWM generator to generate the gate pulse for three phase inverter. In this, Inverter output voltage Vabc is given to the voltage regulator and compare to the Vref to generate the three phase voltage Vabcinv and given to the discrete PWM generator. In voltage regulator park transformation is used to get Vabcto V dq0 and Inverse park transformation is used to get Vdq0 to Vabc. Vd ref. is taken 1 pu and Vq is taken 0 pu.

DER 2 Specifications Two Parallel Inverters 13.8 KV 150 KVA Fig. 3: Block Diagram of Voltage Regulator

TABLE 2: FEEDER LOAD Feeder 1 Feeder 2 Feeder 3

Vabc(pu)

1.0MW, 0.8MW 2.4MW 2KW,2KW

1.0MVAr, 0.8MVAr 1.4MVAr 0,0

III. FORMATION OF MICRO GRID DUE TO DISCONNECTED In the context of the study system of Fig. 1, the 13.8-kV distribution system including the loads and the two DG units constitutes the micro-grid. The disconnected phenomenon that results in the formation of a micro-grid can be due to either intentional or unintentional switching incidents. In the case of an intentional switching microgrid formation appropriate sharing of the micro-grid load amongst the DG units. Intentional the disconnected process results in minimum transients and the micro-grid continues operation, works as an autonomous system. In the context of this paper, only a intentional disconnected of the 13.8-kV system can happen by scheduled opening of the circuit breakers at both ends of the69-kV line, e.g., for line maintenance. Unintentional disconnected means that when fault happen in grid, micro grid is isolated from the remainder of utility system and DGs supply power to load. Disconnected operation improves reliability of power supply.

The abc_to_dq0 Transformation block computes the direct axis, quadratic axis, and zero sequence quantities in a two- axis rotating reference frame for a three-phase sinusoidal signal. The following transformation is used: Vd= +Vcsin( (

2⁄3 (Vasin( + 2 ∕ 3))

Vq= 2⁄3 (Vacos( + 2 ∕ 3))

)

+Vb

) +Vb cos (

V0=1⁄3(Va+Vb+Vc)

sin

(

− 2 ∕ 3) (1)

− 2 ∕ 3) + Vc cos (2) (3)

This transformation is commonly used in three-phase electric machine models where it is known as a park transformation where = rotational speed (red/s) of rotating frame. Va=Vdsin(

)+Vqcos(

)+V0

Vb=Vdsin (

− 2 ⁄3)+Vqcos(

Vc=Vd sin (

+ 2 ⁄3)+Vq cos (

(4) − 2 ∕ 3)+V0 (5) + 2 ∕ 3)+V0 (6)

The dq0_to_abc Transformation block performs the reverse of the so-called Park transformation, which is commonly used in three-phase electric machine models. It transforms three quantities (direct axis, quadratic axis, and


zero-sequence components) expressed in a two-axis reference frame back to phase quantities.

VI. RESULTS AND DISCUSSION A. Grid-Connected Mode

V. CASE STUDY OF MICRO-GRID



Grid voltage, PCC voltage, inverter voltage, diesel engine voltage are 1(pu) and load voltage is less than 1(pu) and frequency is 60 Hz means system is balanced as shown in Fig. 4.



Grid active power is 3MW and grid reactive power is almost 0MVAr. Inverter active power is 21 KW and reactive power is 150 KVAr. Diesel engine active power is 0.75MW and reactive power is almost 2MVAr as shown in Fig. 6.



Grid current, inverter current, diesel engine current is 38 amps, 8 amps, 120 amps respectively as shown in Fig. 6.



The fluctuation in voltage, power or frequency is beard by the main grid.

A. Connection Mode When the micro- grid remains in connection to main grid the operational mode of a micro-grid is called grid connected mode. The components of the above Fig.1 system are identified and modeled using MATLAB/ Simulink software tools. The followings results are obtained.

B. Grid-Disconnected Mode 

The grid voltage is almost 0 (pu). PCC voltage ,inverter voltage ,diesel engine voltage are 1(pu) and load voltage is less than 1(pu) and frequency is 60 Hz after 2 sec ,means system is balanced as shown in Fig.5.



The grid active power is 0MW and grid reactive power is 0MVAr. Inverter active power is 21 KW and reactive power is 150 KVAr. Diesel engine active power is 3.8 MW and reactive power is almost 2MVAr as shown in Fig. 7.



Grid current, inverter current, diesel engine current is 0 amps, 8 amps, 240 amps respectively as shown in Fig. 7.



The fluctuation in voltage, power or frequency is beard by the diesel engine and two parallel connected inverter interfaced source.

Fig. 4: Grid Connected Mode Balanced System

B. Disconnected Mode In the event that a main grid power is lost due to fault or scheduled maintenance, a black out would result, if no suitable control scheme or monitoring system present. This type of isolation of micro-grid from main grid is called disconnected mode operation. The following results come from MATLAB/ Simulink software tools.

Modeling and Control of Micro-Grid under Grid Connected and Disconnected Mode  87

Fig. 5: Grid Disconnected Mode Balanced System

Fig. 6: Grid Connected Mode with Active and Reactive Power


Fig. 7: Grid Disconnected Mode with Active and Reactive Power

VII. CONCLUSION Micro-grid operation of a system based on renewable power generation units is presented in this paper. The micro-grid is supplied by two distributed energy source (DER) units, i.e., a synchronous machine and an electronically interfaced DER unit. The simulation studies show that the two parallel connected inverter unit: can maintain stability of the micro-grid in disconnected transients, through its constant real and reactive power control. The studies also demonstrate that through the fast control of the DER units, the concept of development of control strategies/algorithms for multiple electronically interfaced DERs to achieve optimum response interms of voltage/angle stability. It improves the dynamic voltage profile of the system and especially decreases the difference between pre-disconnected and postdisconnected voltage profile at the load buses. Micro-Grid formation and its autonomous operation are technically viable and merit further in-depth investigation.

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[2]

[3]

[4]

[5]

[6]

[7]

Katiraei, F., Iravani, M.R., and Lehn, P.W.: ‘Micro-grid autonomous operation during and subsequent to islanding process’, IEEE Trans. Power Deliv. , 2005, 20, (1), pp. 248–257. He-Jin Liu; Ke-Jun Li; Hong-Xia Gao; Ying Sun; Kai-qi Sun; WeiJen Lee, "Control and simulation of grid-connected microgrid," Power and Energy Society General Meeting, 2012 IEEE , vol., no., pp.1,6, 22-26 July 2012. M. A. Tabrizi, G. Radman, and A. Tamersi, “Micro Grid Voltage Profile Improvement Using Micro Grid Voltage Controller,” 978-14673-1375-9/12 IEEE. Ahshan, R.; Iqbal, M.T.; Mann, G. K I; Quaicoe, J.E., "Micro-grid system based onrenewable power generation units," Electrical and Computer Engineering (CCECE), 2010 23rd Canadian Conference on, vol., no., pp.1,4, 2-5 May 2010 Xinhe Chen; Wei Pei; Xisheng Tang, "Transient stability analyses of micro-grids withmultiple distributedgenerations," Power System Technology (POWERCON), 2010 International Conference on, vol., no., pp.1,8, 24-28 Oct. 2010. Kumar, K.V.; Selvan, M. P., "Planning and operation of Distributed Generations in distribution systems for improved voltage profile," Power Systems Conference and Exposition 2009.PSCE '09. IEEE/PES, vol., no., pp.1,7, 15-18 March 2009. Zhao Dongmei; Zhang Nan; Liu Yanhua, "Micro-grid connected/islanding operation based on wind and PV hybrid power system," Innovative Smart Grid Technologies - Asia (ISGT Asia), 2012 IEEE , vol., no., pp.1,6, 21-24 May 2012.

A Fuzzy Relation Based Fault Diagnosis System for an Alternator Rajput H.K.

Lini Mathew

Electrical Engg. Department, Vishveshwarya Group of Institutions, Greater Noida, India e-mail: [email protected]

Electrical Engg. Department, NITTTR, Chandigarh, India e-mail: [email protected]

Chatterji S. Electrical Engg. Department, NITTTR, Chandigarh, India e-mail: [email protected] Abstract—A fault diagnosis system using fuzzy relations to deal with the uncertainties of protective relays and circuit breakers’ informations is proposed in this paper. In order to identify faulty section, the fuzzy relations are defined to describe these uncertainly informations. The sagittal diagrams are used to represent the fuzzy relations for alternators, unit auxiliary transformers and bus bars etc. The proposed system presents the section possibility of being faulty with the degree of membership,. The section having high degree of membership is considered to be the faulty section. The LabVIEW based simulation of Thermal Power station may be helpful for working professionals to take decision in critical situations and reduce the delay of restoring actions due to the uncertainties, incompleteness of power system informations. Keywords: Fault Diagnosis System, Fuzzy Relation, Sagittal Diagram

I.

INTRODUCTION

Fault diagnosis is the process to find out the fault in a power system. The aim of the fault diagnosis system is to identify faulted elements in a power station viz. alternators, power transformers, auxiliary transformers and bus bars etc, based on the post fault status of the relays and circuit breakers. It is very essential for working professionals to quickly identify the faulted section on power station prior to start restoring actions. This is required to reduce the outage time and ensure the reliable supply of electric power for consumers. When a fault occurs, the faulty section must be detected and removed from the rest of the power system through a series of relay and circuit breaker operations. Practically, there are several difficulties in locating the faulty sections. If there are some false operation of relays and circuit breakers, the fault may be removed by back up protections. But at the same time, the isolated area is very large and it becomes difficult for load dispatchers to find the faulty section where the first fault occurred. If there are multiple faults at almost the same time, the situation becomes all the more complicated and difficult to judge. This motivates researchers to use Artificial Intelligence approaches, which have suggested the most optimum way to remove

faults and for assisting the operator in order to protect the systems. Different types Expert System (ES) [1-4] have been developed till now. Since dealing with large amount of data is difficult due to the conventional knowledge representation and inference mechanisms. Hence several AI techniques such as, artificial neural networks [5], fuzzy logic [6-8] and neuro-fuzzy [9] has been used to find out the faulty section in a power system. Since, there are some wrong and missed signals in a power system, which may be caused by data transmission error or loss, maloperation and non-operation of circuit breakers and relays, uncertainty reasoning is highly recommended in order to diagnose the system’s faulty section amongst generators, unit auxiliary transformers, service transformers, bus bars etc. The fuzzy relation approach is used to deal with such uncertainties for diagnosing faulty sections in this paper. The proposed scheme has been tested for real faults of a Thermal Power Station, in order to demonstrate the system performance. The tested results indicate that the proposed scheme is an easy reasoning method, along with features like fast diagnosis speed, effectiveness and strong practicability of fault diagnosis.

II.

PROTECTION SCHEME

The protection scheme generally includes Main Protection Relays (MPR), some Back Up Protection Relays (BPR) and circuit breaker failure protection based on the principles as: Level 1: Any faulted equipment should be isolated by its own MPRs and breakers. Level 2: If any associated relays or breakers fail to operate, BPRs should trip the backup breakers to clear the fault. Figure 1. shows the protection scheme of an Alternator at thermal power station. If fault occurs in generator-G4, action of protection relay G4-87G,


takes place to trip the circuit breaker, G4-CB for isolating the generator-G4 from the system. If due to some problem, the circuit breaker does not trip and the faulty section is not isolated, back up protection immediately operates. If

the circuit breaker does not trip again, the breaker failure gives a trip order to B3CB1, B3CB2, ST2CB and G5CB for isolating generator G4, from the system network. B3CB2

B3CB1 G4 BF ST2 CB

G4CB

G5CB

G4-87 G G4-87 TG

T4 T5 T4 T4

T5

G4-64 G G4-59 G G4-46

G4-40GZ G4 G4 G4 G4 G4 G4

G4-30 EX

G5

G4-21 I G4-21 II

G4-98 G4-37 G4-32 G4-32 YT G4-2/11 A G4-2/7 A G4-30 X

UAT 4ACB

UAT 4BCB

U/v

U/V

30 D

30 G

30 E

30 H

30 F

30 J

30 K

30 L

50-T4A

50-T4B

87 T 4A

87 T 4B

Fig.1 A Typical. Protection Scheme of an Alternator

III. FUZZY RELATIONS & SAGITTAL DIAGRAMS We, in the present work proposed a method to solve the problem of locating faults based on fuzzy relations.

This method utilizes information as operating time sequences of the actuated relays and operation of tripped circuit breakers. The method builds a sagittal diagram for

A Fuzzy Relation Based Fault Diagnosis System for an Alternator  91

alternator to represent operating conditions of the relays and circuit breakers during a fault. The degree of membership is then calculated by fuzzy arithmetic. This degree of membership is used to determine the maximum likelihood of the fault location. A crisp relation represents the presence or absence of association, interaction, or 0.8 0.8 0.75 0.65

interconnectedness between elements of two or more sets. Any relation between two sets (let X and Y) is known as binary relation, and is usually denoted by R(X, Y). This concept can be generalized to allow various degrees or strengths of relation or interaction between elements. 0.8

G4-87 G4-87 G G G4-87 G4-87 TGTG

0.9 0.9 0.85 0.75

G4-64 G4-64 G G G4CB G4-59 G4-59 G G 0.7 0.75 0.8 0.65

G4-40 G4-40 GZGZ G4-30 G4-30 EXEX

0.8 0.85 0.9 0.75

G4-98G4-98 G4 G4 G-4 G4 G5CB

G4-37G4-37 0.6 0.5 0.7 0.8 0.8

G4-32G4-32 G4-32 G4-32 YTYT

0.7 0.6 0.8 0.9 0.9

B3CB1

G4-2/11 G4-2/11 A A G4-2/7 G4-2/7 A A B3CB2

G4-30 G4-30 X X 0.6 0.6 0.55

G4-46G4-46 G4-21 G4-21 I,II I,II

ST2CB

G4-BF G4-BF

Fig. 2: Sagittal Diagram for an Alternator

Degrees of associations can be represented by membership grades in a fuzzy relation. A binary fuzzy relation can be represented by a sagittal diagram. Each of the sets X, Y is represented by a set of nodes in the diagram. Elements of X x Y with nonzero membership grades in R(X, Y) are represented in the diagram by lines connecting the respective nodes. These lines are labeled with the degree of membership. Sagittal diagram for alternator of a Thermal power station is shown in Fig.2. The Sagittal diagram consists of three sets of nodes; viz. set 1-sections, set 2-relays and set 3-circuit breakers. Section may be alternator, power transformer, service transformer, unit auxiliary transformer and busbar etc. When fault occurs in any section of set-1, it will cause the operation of any relay of set-2 and then the relay will send signal to trip the circuit breaker of set-3. 0.7

The labeled relation values between the section-set, relay-set and circuit breaker-set are taken according to the uncertainties of operation of and priorities of relays and circuit breakers when a fault occurs [10-12]. The value of label lies in between 0 and 1. Considering the characteristics of operation of relays and circuit breakers, circuit breakers contain fewer uncertainties as compared to relays do. Relays use information on power transmission line dozens of kilometers away, and the information is transmitted to relays by the line exposed outside whereas circuit breakers are only about 10 meters away from relays and the information transmission line is well protected against disturbances. Therefore the labels between relay and circuit breakers are set larger than the labels between sections and relays. In case of a busbar, the degree of membership is adjusted according to the number of lines to a bus. In other words as the number of lines connected


to a bus increases, uncertainty increases, hence smaller labels are preferred.

Start Start

IV. DIAGNOSIS PROCEDURE Status scans of protected relays and circuit breakers

A. Operation of Fuzzy Sets The union of two fuzzy sets A and B is generally specified by a function of the form

No

Change of Relay status?

u:[0,1] x [0,1] → [0,1] (1) For each element x of universal set, this function takes its arguments as a pair consisting of the For each element x of universal set, this function takes its arguments as a pair consisting of the element’s membership grades in set A and in set B and yields to the membership grade of the element in the set constituting the union of A and B. Hence, (AUB)(x) = u [A(x), B(x)], for all x

Yes

No

Yes Change of CB status?

X (2)

Till now several classes of functions have been proposed whose individual members satisfy all the axiomatic requirements for the fuzzy union [14]. One of these classes of fuzzy unions is known as the Yager class, defined by the following equation [14]

Yes Calculate the faulty section membership

Print the diagnosis results

uw ( a, b ) = min (1, ( aw + bw )1/w), (3) where the values of the parameter w are selected from a range of 1 to ∞ to get unions of various strengths. Similarly the fuzzy intersection of the Yager class is defined by the following equation [14] iw( a, b ) = 1-min (1, [ ( 1-a )w + ( 1-b )w]1/w), (4) Considering the characteristic of power station, w = 3 is chosen in this paper.

B. Diagnosis To identify the faulty section, the decision making procedure is stepped as follows: 1.

When the faults occur in the power station, consider the operated sections, relays and circuit breakers through set1, set2, set3.

2.

If path is complete, derive the fuzzy intersection of the labels of lines that make a path.

3.

Derive the unions of step 2’s results for the paths connected to one section.

4.

Compare the unions determined as the degree of membership of the section’s being faulty in step 3. The section having high degree of membership will be the desired faulty section.

C. Fault Diagnosis Program The flow chart of the fault diagnosis program is shown in Fig.3.

Stop Fig. 3: Flow chart of Fault Diagnosing Program

V. IMPLIMENTATION The authors prepared an expert system for real power station. Table (I) presents two fault cases and their diagnosis indicating membership value of the faulty section. The LabVIEW programs for each section have been developed on the basis of their sagittal diagrams. In case 1 the differential relay, BB30/96JX and Negative phase sequence relay, G4-46 operated and circuit breakers; B3CB1, B3CB2, G4CB, G5CB, ST2CB tripped as shown in fig.4. As membership value of busbar block3, BB3 is higher than that of generator, G4; the faulty section is busbar block-3, BB3. In case 2 both differential and inter-turn protection G4-87G, G4-87TG are operated showing high degree of certainty of fault in generator, G4.

VI. CONCLUSION In the present work, the investigator proposed an expert system to deal with the uncertainties of power system information using fuzzy relations. The sagittal diagram is used to represent the fuzzy relations for alternator and hence to find out faulty section by the fuzzy relation operation. The proposed method presents the section possibility of being faulty with the degree of membership. LabVIEW based simulation can

A Fuzzy Relation Based Fault Diagnosis System for an Alternator  93

help the operator to make the right decision in critical situations and reduce the delay of restoring actions due to the uncertainties’, TABLE 1. FAULTS AND THEIR DIAGNOSIS Fault Relays Case Operated 1

2

BB30/96JX, G4-46 G4-87G, G4-87TG

Circuit Breakers Tripped

Power Station’s Analysis

Fuzzy Diagnosis Results Faulted Members Section hip Value B3CB1,B3 Differential Bus bar 0.791992 CB2, Relay: block-3, G4CB,G5C Right BB3 B, Operation ST2CB G4CB Differential Generator 0.997847 & Inter-turn , G4 fault Relay: Right Operation

[1]

[3]

[4] [5]

[6]

[7]

[8] [9]

Incompleteness of protective relays and circuit breakers information. tested results show that the proposed technique is easy reasoning and has fast diagnosis speed.

[10] [11]

VII. APPENDIX A 87 G

Differential

87

TG Inter-turn

64 G

Stator ground

59 G

Over excitation

40 GZ

Loss of field

30 EX

Excitation protection

98

Pole slipping

37

Low forward power

Anti-motoring

2/11 A

Damper tank emergency

2/7 A

Stator water flow too low

30 X

Resistivity too low

46

Negative phase sequence

21

Back-up impedance stage-I,II

BF

Breaker failure

REFERENCES

[2]

Fig. 4: Activated Path Indicating Membership Value of Faulty Section (Generator, G4)

32

[12]

[13]

[14] [15]

C. Fukui, J. Kawakami, “An expert system for fault section estimation using information from protective relays and circuit breakers”, IEEE Transactions on Power Delivery, Vol. 1, No.4, pp 83-90, October, 1986. Eleri Cardozo, Sarosh N. Talukdar, “A distributed expert system for fault diagnosis”, IEEE Transactions on Power System, Vol.3, No.2, pp 641-646, May, 1988. C. A. Protopapas, K. P. Psaltiras, A. V. Machias, “An expert system for substation faults diagnosis and alarm processing”, IEEE Transactions on Power Delivery, Vol. 6, No.2, pp 648-655, April, 1991. Y. M. Park, G. W. Kim, J. M. Sohn, “A logic based expert system (LBES) for fault diagnosis of power system”, IEEE Transactions on Power System, Vol.12, No.1, pp 363- 369, February, 1997. H. Yang, W. Chang, C. Huang, “A new neural networks approach to on-line fault section estimation using information of protective IEEE Transactions on Power relays and circuit breakers”, Delivery, Vol. 9, No.1, pp 220-230, January, 1994. C. S. Chang, J. M. Chen, D. Srinivasan, F. S. Wen, A. C. Liew, “Fuzzy logic approach in power system fault section identification”, Proceedings of the IEE Generation, Transmission and Distribution, Vol.144, No.5, pp 406-414, September, 1997. Hong-Chan Chin, Cheng-Pin Lin, “On-line fault diagnosis of distribution substation using fuzzy reasoning”, Proceedings of the IEEE / PES Transmission and Distribution Conference & Exhibition, Vol.3, pp 2086-2090, 6-10 October, 2002. H. C. Chin, “Fault section diagnosis of power system using fuzzy logic”, IEEE Power Engineering Review, December, 2002. Ye XU, Zhuo Wang, “On a fault detection system based on neurofuzzy fusion method”, Proceedings of the IEEE Chinese Control and decision Conference, pp 3190-3193, 26-28 May, 2010. H. J. Cho, J. K. Park, “An expert system for fault section diagnosis of power system using fuzzy relations”, IEEE Transactions on Power System, Vol.12, No.1, pp 342-348, February, 1997. S. Min, J. Park, K. Kim, I. H. Cho, H. J. Lee, “A fuzzy relation based fault section diagnosis method for power systems using operating sequence of protective devices”, Proceedings of the IEEE Power Engineering Society Summer Meeting, Vol.2, pp 933-938, 2001. Wael M. Soliman, Bahaa El Din H. Soudy, Mohamed A.A. Wahab, M. M. Mansour, “Power generation station faults diagnosis based on fuzzy relations using information of protective relays and circuit breakers”, Proceedings of the IEEE International Conference on Electric Power and energy Conversion System, pp 1-6, 10-12 November, 2009. Rajput. H. K., Lini Mathew and Chatterji. S, “Fault Diagnosis System for Power Station using Fuzzy Relations”, Proceedings of the International Conference on Computer Applications in Electrical Engineering Recent Advances: Smart Grid Technologies, 3-5 October, 2013. G. J. Klir, B. Yuan, “Fuzzy Sets and Fuzzy Logic, Theory And Application”, Prentice Hall, 1995. T. J. Ross, “Fuzzy Logic with Engineering Applications”, WILEY Publications, 2009.

Transmission Network Expansion Planning Using Genetic Algorithm Raminder Kaur

Tarlochan Kaur

Assistant Professor, PEC University of Technology, Chandigarh e-mail: [email protected]

Associate Professor, PEC University of Technology, Chandigarh e-mail: [email protected]

I.

INTRODUCTION

Transmission planning is an important component of power system planning. It determines the characteristics and performance of the future electric power network and influences the operation of power system directly. Transmission expansion planning must answer these questions: where to build a new transmission line, what kind of transmission line to be built, and when to build it. So it searches for the best connection plan between forecasted loads and foreseen generation plan.[1] Calculus based methods i.e. indirect and direct methods have been used to solve TNEP problem have some drawbacks. Indirect methods seek local extrema by solving the usually non-linear set of equations resulting from setting the gradient of the objective function equal to zero. on the other hand, direct search methods seek local optima by hopping on the function and moving in a direction related to the local gradient. Drawbacks of both the methods : First, both methods are local in scope, the optima they seek are the best in a neighborhood of the current position. So there is surely a chance of missing the main event. Second, calculus based methods depend upon the existence of derivatives, this is a severe shortcoming. Genetic algorithm is an example of a search procedure that uses random choice as a tool to guide a highly exploitative search through a coding of a parameter space. Genetic algorithm is a robust optimization technique that works above a set of candidate solutions named population and performs a number of operations based on genetic mechanical. As in the evolutionary theory, genetic algorithm performs the mechanisms of crossover and mutation, which have the purpose of recombining the genetic material existing in the mating pool. so that better individuals may be created and the search enlarged to other regions of the space.[4] The comparison of general purpose algorithms and highly specified algorithms can be analysed by the fig as shown below which shows that the general purpose algorithms like genetic algorithms are more efficient for complex problems. The overall response of the algorithm is far better with the increase in the complexity of the problem.

Fig 1: Performance Comparison of Two Types of Algorithm

II.

GENETIC ALGORITHM

Genetic algorithm is an adaptive heuristic search based on the evolutionary ideas of natural selection and genetics. As such they represent an intelligent exploitation of a random search used to solve optimization problem. Although randomized, genetic algorithm are by no means random; instead they exploit the historic information to direct the search into the region of better performance within the search space. Genetic algorithm is a robust optimization method that works about a set of candidate solution (individuals ) named population and performs a number of operation based on genetic mechanical. such operator recombine the information contained in the individuals and then, they create new populations. The basic techniques of the genetic algorithm are designed to simulate processes in natural systems necessary for evolution ; especially those follow the principles first laid down by Charles Darwin of ”survival of the fittest”. Since in nature, competition competition among individuals for scanty resources result in fittest individuals dominating over the weaker ones. Genetic algorithm starts the optimization processes from an initial population. new populations are generated by an evolution mechanism comprising selection, crossover and mutation, and which gradually leads to individuals with higher performance indices. The selection mechanism tends to guide the solution to local optimal points. the mutation mechanism on the other hand helps exploring the neighborhood of a configuration and thus has an important role in searching for local optimal solution (this is also known as intensification, as opposed to diversification mention above).[4]

Transmission Network Expansion Planning Using Genetic Algorithm  95

III. WHY GENETIC ALGORITHM OTHER THAN OTHER METAHEURISTIC TECHNIQUES Unlike older AI systems, genetic algorithm does not break easily even if the inputs changed slightly, or in the presence of reasonable noise. Also, in searching the large state space, multi level state space, or n dimensional surface, a genetic algorithm may offer significant benefits over more typical search of optimization techniques (linear programming, heuristic, depth first, breath first, and praxis) A genetic algorithm is an heuristic used to find approximate solutions to difficult to solve problems through application of principles of evolutionary biology to computer science. genetic algorithm use biologically diverted techniques such as inheritance, mutation, natural selection, and recombination (or crossover). Genetic algorithm are a particular class of evolutionary algorithm. Genetic algorithm are typically implemented as a computer simulation in which a population of abstract representations (called chromosomes) of candidate solutions (called individuals ) to an optimization problem evolves toward better solution.[5]

IV. BIOLOGICAL BACKGROUND A. Chromosomes All living organisms consists of cells. In each cell there is the same set of chromosomes. Chromosomes are strings of DNA and serve as a model for the whole organism. A chromosome consists of genes, blocks of DNA. Each gene encodes a particular protein. Possible setting for a trait are called alleles. Each gene has its own position in the chromosome. This position is called locus.

point in the search space represents one possible solution. Each possible solution can be marked by its value for the problem. With GA we look for the best solution among the number of possible solutions–represented by one point in the search space. Looking for a solution is then equal to looking for some extreme value (minimum or maximum) in the search space. At times the search may be well defined, but usually we know only a few points in a search space. In the process of using GA, the process of finding solution generate other points as evolution proceeds.

Fig. 2: Example of a Search Space

The problem is that the search can be very complicated. one may not know where to look for solution or where to start. There are many methods one can use for finding a suitable solution, but these methods do not necessarily provide the best solution. Some of these methods are hill climbing, tabu search, simulated annealing and the genetic algorithm. The solution found by these methods are often considered as good solutions, because it is not often possible to prove what the optimum is.

V. OPERATORS OF GA Crossover and mutation are most important parts of genetic algorithm. The performance are influenced mainly by these two operators.

A. Encoding of Chromosomes

Complete set of genetic material (all chromosome) is called genome. Particular set of genes in genome is called genotype. The genotype is related with later development after birth base after organism’s phenotype, its physical and mental characteristics, such as eye color, intelligence etc.

A chromosome should in some way contain information about solution that it represents. The most used way of encoding is the binary string. Each chromosome is represented by a binary string. Each bit in the string can represent some characteristics of the solution. Of course, there are many other ways of encoding.

B. Reproduction

The encoding depends mainly on the solved problems. For example one can encode directly integer or real numbers; sometimes it is useful to encode some permutations and so on.

During reproduction recombination first occurs. Genes from parents combine to form a whole new chromosomes. The newly created offspring can then be mutated. Mutation means that the elements of DNA are a bit changed. the changes are mainly caused by errors in copying genes from parents. The fitness of an organism is measured by success of the organism in its life.

C. Search Space If we are solving a problem we are usually looking for some solution which will be the best among others. The space of all feasible solutions is called search space. Each

B. Crossover After we have decided that what encoding we will use, we can proceed to crossover operation. Crossover operators on selected genes from parent chromosomes and creates new offspring. The simplest way how to do that is to choose randomly some crossover points and copy everything before this point from the first parent and then copy everything after the crossover point from the other parent.


There are other ways to make crossover, for example we can choose more crossover points. Crossover can be quite complicated and depends mainly on the encoding of chromosomes. Specify crossover made for a specific problem can improve performance of the genetic algorithm.

C. Mutation After a crossover is performed, mutation takes place. Mutation is intented to prevent falling of all solutions in the population into a local optimum of the solved problems. Mutation operation randomly changes the offspring resulted from crossover.In case of binary encoding we can switch a few randomly chosen bits from 1 to 0 or from 0 to 1. The techniques of mutation depends mainly on the encoding of chromosomes. For example when we are encoding permutation, mutation could be performed as an exchange of two genes.

other hand if there are too many chromosome, GA slows down. Very big population size does not improve performance of genetic algorithm. Good population size is 20-30, sometimes 50-100 are reported the best. 4.

Selection: Chromosome are selected from the population to be parents for crossover. According to Charles Darwin’s theory the best one survive to create new ones. Few methods of selecting the chromosome are discussed below:

Roulette wheel selection: Parents are selected according to their fitness. Imagin a roulette wheel where all the chromosome in the population are placed. The size of selection in the roulette wheel where all the chromosome in the population are placed. The size of selection of the roulette wheel is proportional to the value of the fitness function of every chromosome-the bigger the value is the larger the section is. See the following picture for an example.

1) Effects of genetic operators 

Using selection alone will tend to fill the population with copies of the best individuals from the population.



Using selection and crossover operators will tend to cause the algorithms to converge on a good but sub optimal solution.



Using mutation alone induces a random walk through the search space.



Using selection and mutation creates a parallel, noise-tolerant, hill climbing algorithm.

2) Parameters of genetic algorithm 1.

Crossover over probability: If there is no crossover off springs are exact copies of parents. If there is crossover, offsprings are made from parts both parents chromosomes. Crossover is made in hope that new chromosomes will contain good part of old chromosomes. However it is good to leave some of the old population survive to next generation.

2.

Mutation probability: If there is no mutation offspring are generated immediately after crossover without any change. If mutation is performed one or more part of chromosome are changed. it prevents the genetic algorithm from falling into local extremes. Best rate for mutation is.5 %–1%.

3.

Population Size If there are too few chromosomes, genetic algorithm has few possibilities to perform crossover and only a small part of search space is explored. On the

Fig. 3: Roulette Wheel Selection

A marbel is thrown on the roulette wheel and the chromosome wheel and the chromosome where it stops is selected. Clearly the chromosome with bigger fitness value will be selected more times. The previous type of selection will have problems when there are big differences between the fitness value. For example if the best chromosome fitness is 90 % of the sum of all fitness’s then the other chromosome will have very few chances to be selected.

Fig. 4: Simulation before Ranking (Graph of Fitness)

Fig. 5: Simulation after Ranking (Graph of Order Numbers)

Rank selection ranks the population first and then every chromosome will receive fitness value determined


the first parent, and the rest is copied from the other parent.

by this ranking. The worst will have the ranking 1, second worst 2and the best will have fitness N. 

Steady State Selection In this type of selection the big part of chromosome can survive to next generation. In every generation a few good chromosome(with higher fitness) are selected for creating new offspring. Then some bad chromosome(with lower fitness) are removed and the new offspring are placed in their place. The rest of population survives to new generation. Tournament Selection: It is simple but efficient method of sampling that consist of randomly selecting apredefined number of individuals and then, pick from this sample the one with the largest fitness value. This process is repeated N times( N is the population size). All methods above rely on global population statics.



Could be a bottle neck especially on parallel machines.



Relies on presence of external fitness function which might not exist; eg. Evolving game players.

Fig. 6: Single Point Crossover



Two point crossover Two crossover point are selected, binary string from the beginning of the chromosome to the first crossover point is copied from the first parent, the part from the first to the second crossover point is copied from the other parent and rest is copied from first parent again.

Fig. 7: Two point Crossover



Uniform Crossover Bits are randomly copied from the first or from the second parent.

Informal procedure: 

Pick K members at random then select the best of these.



Repeat to select more individuals [6]

1.

Elitism: The idea of the elitism has been already introduced. when creating the new population by crossover and mutation, we have a big chance, that we will loose the best chromosome. Elitism copies the best chromosomes the new population. The rest of the population is constructed in ways described above. Elitism can rapidly increase the performance of GA, because it prevents loss of best found solution.

2.

3.

Encoding: Encoding of chromosomes is the first question to ask when starting to solve a problem with GA.

Fig. 8: Uniform Crossover



Arithmetic Crossover Some arithmetic operation is performed to make a new offspring.

Fig. 9: Arithmetic Crossover

D. Binary Encoding Mutation 

Bit inversion selected bits are inverted.

Crossover and mutation: Crossover and mutation are two basic operators of GA. Performance of GA depend on them very much. The type and implementation of operators depends on the encoding and also on the problem. Fig. 10: Bit inversion Mutation

3) Binary encoding crossover 

Single Point Crossover One crossover point is selected, binary string from the beginning of the chromosome to crossover point is copied from

E. Permutation Encoding Crossover Single point crossover One crossover point is selected, the permutation is copied from the first parent till the


crossover point, than other parent is scanned and if the number is not yet in the offspring, it is added. (1 2 3 4 5 6 7 8 9) + (4 5 3 6 8 9 7 2 1)= (1 2 3 4 5 6 8 9 7)

F. Permutation Encoding Mutation Order changing: Two numbers are selected and exchanged (1 2 3 4 5 6 8 9 7)= (1 8 3 4 5 6 2 9 7) Value encoding crossover: All crossover from binary encoding can be used Value encoding mutation: Adding a small number (for real value encoding)-a small number is added to (or subtracted from )selected values (1.29 5.68 2.86 4.11 5.55 ) =>(1.29 5.68 2.86 4.11 5.55) Tree encoding Crossover: One crossover point is selected in both parents, parents are divided in that point and the parts below crossover points are exchanged to produce new offspring.

Fig. 2: Tree Crossover

Tree encoding mutation Changing operator, numberselected nodes are changed Proposed Approach When a genetic algorithm is used for solving a combinatorial optimization problem, the set of parameters should be adjusted in so far as different runs are performed, among these parameters, the penalty factor α of the objective function requires special attention since it has a decisive influence on the performance of the genetic algorithm for the transmission network expansion planning problem. Whenever high values of α is used, the genetic algorithms will over-stimulate individuals having low levels of loss of load and ‘super-individuals’ will take over the early populations. Therefore search will certainly converge to a sub-optimal solution, no matter which set of remaining parameters are used. Thus, a more secure and consistent procedure for solving the problem consists on performing several runs of the genetic algorithms with different low values of α. Due to this, in each run the genetic algorithm converges to a unfeasible solution i.e. towards a solution with a loss of load. So, different unfeasible solutions can be obtained by slightly increasing the penalty factor run by run. Thereby, the approach we are proposing for solving the transmission network expansion planning problem consists on the construction of the loss of load limit curve for the transmission system under study, starting from the

unfeasible solutions found by the genetic algorithm. Although the approximate cost of the optimum solution can be estimated in advance through the loss of load limit curve, the optimum transmission configuration is unknown. Nevertheless, it can be obtained by performing a fine adjustment of the penalty factor α until the genetic algorithm finds out a feasible solution, staring from the unfeasible solution located near the touching point of the curve over the investment axis.[7] Note that search space is larger when higher levels of loss of load are permitted. In this example, search space limits are shown for levels of 0(feasible region), 20, 40, and 60 MW and some unfeasible solutions found by the genetic algorithm can also be seen among all the solutions, the dominant ones define the loss of load limit curve, which reaches the feasible region at the global optimum solution, which is also emphasized.

VI. ALGORITHM USED Step 1: Generate initial population by random generation; the size of initial population taken is 30. Step 2: For each member of population generate random values of nodal voltage angle satisfying the constraints on the nodal voltage angles. Step 3: Calculate the total loss of the load for each member of the population. Step 4: Form a fitness function equal to inverse of loss of load. Step 5: Apply tournament selection to select those members which are having lesser loss of load i.e. higher fitness value. Step 6: Perform crossover operation according to its fitness value determined. Step 7: Select the minimum value of loss of load after performing iterations. Step 8: Calculate the cost for each member for the loss of load value calculated above. Step 9: Form the main fitness function equal to inverse of cost calculated above Step 10: Apply tournament selection to select those members which are having lesser loss of load i.e. higher fitness value Step 11: Perform crossover operation according to its fitness value determined. Step 12: If the minimum cost obtained does not improve after three or four iterations, then perform mutation


Step 13: Let the GA run for no. of iterations predetermined. If the no. of iterations is less than say 1000 then go to step 2. Step 14: Print the minimum cost and the configuration of the network.

VII. GARVER TEST SYSTEM CASE STUDY The Garver 6 bus test system has a six buses and 15 right-of-ways for the addition of new circuits. The relevant data are given in Table 1 and 2. This system has become the most popular test system in transmission expansion planning. The initial topology is shown below: generation capacities of buses 1, 3, and 6 are 150, 360, and 600MW, respectively. Loads for buses 1 to 5 are 80, 240, 40, 160 and 240MW. Table shown below presents the basic circuit =5MW and α= 10. data. Additional data are

Fig. 12: IEEE 6 Bus Network TABLE 1: GENERATION AND LOAD DATA FOR 6-BUS SYSTEM

TABLE 2: BRANCH DATA FOR 6-BUS SYSTEM 1–2 1–3 1–4 1–5 1–6 2–3 2–4 2–5

1 0 1 1 0 1 1 0

0.40 0.38 0.60 0.20 0.68 0.20 0.40 0.31

100 100 80 100 70 100 100 100

40 38 60 20 68 20 40 31

2-6 3-4 3-5 3-6 4-5 4-6 5-6

0 0 1 0 0 0 0

0.30 0.59 0.20 0.48 0.63 0.30 0.61

100 82 100 100 75 100 78

30 59 20 48 63 30 61

From the above given data we can have the system network equations.

A. Results for IEEE 6-bus Network System The programming in C++ environment with the help of VB C++ 6.0 is done. The network constraints as well as fitness function is already placed the program. The equations are then made to operate on random solutions with the help of random function. This program provides the required minimum investment cost which is our main fitness function and has to reduce the minimum value. This program also provides the required configuration of then network for which the minimum cost be obtained. Although, some non-optimal solutions are obtained, but they are neglected because we need optimal solutions. TABLE 3: OPTIMAL SOLUTIONS OBTATINED FOR IEEE 6-BUS NETWORK

1 2 3 4 5

0 0 1 1 0

4 3 3 4 5

1 1 0 0 1

2 3 3 2 1

200 200 200 200 200

Fig. 13: Network After Implementing Genetic Algorithm

VIII.

CONCLUSION

The selection process in genetic algorithm is used to select the better solutions from the present random population. The solutions then moved to crossover operation. the crossover operation is known for intensification. it searches the better solution in the region nearby it. the mutation operator is used for diversification.


The strength of two lies in their unity. If one of them is not used, then it may possible that one may not find the ultimate optimal solution. The result obtained are very near to the optimal solutions are obtained and compared with garver’s optimal results. Through this proposal, optimum solutions can be obtained in a reliable and consistant way by performing few runs of the genetic algorithm. In the cases studied, the maximum deviation of the cost estimate was less than 1% in relation to the cost of the optimal solution. We can apply this work with a bigger size transmission networks.

[8]

[9]

[10]

REFERENCES [1]

[2]

[3]

[4] [5] [6] [7]

Levi, V.A., Calovic, M.S. “A new decomposition based method for optimal expansion planning of large transmission networks”; Power Systems, IEEE Transactions on Vol. 6, No. 3,Aug. 1991, Page(s): 937–943. G.c. Otiveira; A.P.C. Costa; S. Binato, “Large Large scale transmission network planning using optimization and heuristic techniques”; Power Systems, IEEE Transactions on Vol. 10, No. 4 ,November 1995,Page(s): 1828-1834 Da Silva, E.L. ; Gil, H.A. ; Areiza, J.M. “Transmission network expansion planning under animproved genetic algorithm” Power Systems, IEEE Transactions on Vol. 15, NO. 3 Aug 2000, Page(s): 1168-1174. Goldberg, David E, “Genetic Algorithms in Search, Optimization and Machine Learning”,(1989) Kluwer Academic Publishers, Boston, MA. Mori, H.; Sone, Y.; “Parallel tabu search based approach to transmission network expansion planning”; Power Tech proceedings,2001 IEEE Porto Vol. 2, sept 2001 Page(s):6 pp. vol.2. http://www.cs.vu.nl. N. Chaiyaratana; A.M. S. Zalzala, “Recent Developments in Evolutionary and Genetic Algorithums: Theory and Applications”; Genetic Algorithms in Engineering Systems: Innovations and Applications, Sept 1997, Conference Publication No.446,IEEE 1997

[11]

[12]

[13]

[14]

Pan Zhiqi; Zhang Yao; Zheng Fenglei, “Application of an improved genetic algorithum in transmission network expansion planning” ; Advances in Power System Control, Operation and Managements, 2003. ASDCOM 2003. Sixth International Conference on (Conf. Publ. No. 497) Volume 1,11-14 Nov. 2003 Page(s):318-326. Xie Jingdong; Tang Guoqing, “The Appllication of Genetic Algorthiums in the Multi-Objective Transmission Network Planning”; Proceedings of the 4th Iinternational Conference on Advances in Power System Control, operation and management, APSCOM-97, Hong Kong, Nov 1997. Tangkananuruk, W. ; Dept. of Electr. Eng., Kasetsart Univ., Bangkok ; Damrongkulkamjorn, P. “Multi-zone transmission expansion planning using genetic algorithm”, Electrical Engineering/Electronics, Computer, Telecommunications and Information Technology, 2008. ECTI-CON 2008. 5th International Conference on (Volume:2 ) Karbi Garces, L. ; Dept. of Electr. Eng., Paulista State Univ., Sao Paulo, Brazil ; Romero, R “Specialized Genetic Algorithm for Transmission Network Expansion Planning Considering Reliability” Intelligent System Applications to Power Systems, 2009. ISAP '09. 15th International Conference, 2009. Flores, B.F. ; Electr. & Electron. Eng. Inst., Univ. of the Philippines, Diliman, Diliman, Philippines ; Salonga, J.H.M. ; Nerves, A.C., “Multi-objective Transmission Expansion Planning Using an Elitist Non-dominated Sorting Genetic Algorithm with Fuzzy Decision Analysis”, Modelling Symposium (AMS), 2011 Fifth Asia. Carrano, E.G. ; Dept. of Electr. Eng., Univ. Fed. de Minas Gerais, Belo Horizonte, Brazil ; Takahashi, R.H.C. ; Cardoso, E.P. ; Saldanha, R.R. “Optimal substation location and energy distribution network design using a hybrid GA-BFGS algorithm”, Generation, Transmission and Distribution, IEE Proceedings(Volume:152, Issue: 6 ), 2005. Gaun, A. ; Inst. of Electr. Power Syst., Graz Univ. of Technol., Graz, Austria ; Rechberger, G. ; Renner, H.” Probabilistic reliability optimization using hybrid genetic algorithms”, Electric Power Quality and Supply Reliability Conference (PQ), 2010

Power Quality Problems: A Review Raminder Kaur

Gagandeep Singh

Assistant Professor, EED, PEC University of Technology, Chandigarh e-mail: [email protected]

ME Electrical, EED, PEC University of technology, Chandigarh e-mail: [email protected]

Abstract—In today’s era of interconnected power system, quality of power has become important for both the utility and the consumers. Problems related to Power quality have become important to electricity consumers at all levels of usage. Sensitive equipment and non-linear loads are mostly being used in both the industrial commercial sectors and the domestic environment. The software and IT industry is the biggest user of semiconductor devices, and consumer electronics. Due to the continuous use of drive systems (rotating machines, controlling thyristor and associated electronic components) in industry and in power stations, electronic equipment are becoming an integral part of today’s industrial, institutional, and commercial facilities. Unfortunately, this type of equiptment often generates power supply disturbances, which in turns affect other items of equipment, and are more likely to generate the distorting harmonics. These harmonics can cause inefficient operations of AC motors and can be a source of premature equipment failure that will halt production in industrial processing, data processing activities in real time such as banking transaction processing may be lost, etc. This paper presents the most common power quality problems, their causes &effect, the ways of monitoring PQ problems present in a power system.

I.

INTRODUCTION

Engineers have always been concerned about the quality of power. They see power quality as anything that affects the voltage, current, and frequency of the power being supplied to the end user. The utility aims to supply its customers with clean & hazardous free electric power and the customers expect cheap & reliable quality of electricity, so that its equipment shall work properly and efficiently. The term “power quality” should be interpreted as service quality, encompassing the three aspects of reliability of supply, quality of power offered, and provision of information [1].

This paper presents the review of power quality issues and related standards, PQ problem causes and effects on various part of power system and interconnected devices. Further various PQ measuring methods a n d s o m e correction methods are proposed with giving a thorough knowledge of harmonics, power quality indices, parameters effecting electric power etc.

II.

POWER QUALITY PROBLEM

This IEEE defined power quality disturbances shown in this paper have been organized into seven categories based on wave shape:

A. Transients The term transients has been used in the analysis of power system variations for a long time. Transients fall into two subcategories: 1.

Impulsive

2.

Oscillatory

B. Impulsive Impulsive transients are sudden high peak events that raise the voltage and/or current levels in either a positive or a negative direction. Impulsive transients can be very fast events (5 ns) rise time from steady state to the peak of the impulse of short-term duration (less than 50 ns). Example: Positive impulsive transient caused by electrostatic discharge (ESD)

Power quality is defined in the IEEE 100 Authoritative Dictionary of IEEE ( Institute of Electrical and Electronic Engineers) Standard Terms as: “The concept of powering and grounding electronic equipment in a manner that is suitable to the operation of that equipment and compatible with the premise wiring system and other connected equipment.” The term power quality issue has taken new dimensions due to restructuring and shifting trend towards distributed generations in power system. Huge loss in terms of time and money has made power quality problems a major anxiety for modern industries with nonlinear loads in electrical power system.

Fig. 1: ESD Impulsive Transient

C. Oscillatory An oscillatory transient represents sudden change in the steady-state condition of voltage, current, or Both


signal, at both the positive and negative signal limits, oscillating at the natural system frequency. Oscillatory transients usually decay to zero within a cycle (a decaying oscillation). These transients occur when you turn off an inductive or capacitive load, such as a motor or capacitor bank.

connections, sudden load reductions, and a single-phase fault on a three-phase system are common sources of Swell.

Fig. 5: Swell

G. Waveform Distortion There are five primary types of waveform distortion:

Fig. 2: Oscillatory Transient

DC offset Direct current (dc) can be induced into an ac distribution system, often due to failure of rectifiers within the many ac to dc conversion technologies. Overheating and saturation of transformers can be the result of circulating dc currents.

An interruption occurs when the supply voltage or load current decreases to a value less than 0.1 p.u for a period of time not exceeding 1 min. Depending on its duration, an interruption is categorized as instantaneous, momentary, temporary, or sustained. Duration range for interruption types are as follows:

Fig. 6: DC Offset

D. Interruption



Instantaneous: 0.5 to 30 cycles



Momentary: 30 cycles to 2 seconds



Temporary: 2 seconds to 2 minutes



Sustained: greater than 2 minutes

H. Harmonics Harmonic distortion is the corruption of the fundamental sine wave at frequencies that are multiples of the fundamental. (e.g., 150Hz is the third harmonic of a 50Hz fundamental frequency; 3 X 50 =150).

Fig. 6: Harmonic Waveform

I. Fig. 3: Interruption

Interharmonics

A sag is a reduction of AC voltage at. Sags are usually caused by system faults, and are Short duration under-voltages are called “Voltage Sags” or “Voltage Dips [IEC]”. A sag is a reduction in the supply voltage magnitude at a given frequency for the duration of 0.5 cycles to 1 minutes time followed by a voltage recovery after a short period of time.

A type of waveform distortion that are usually the result of a signal imposed on the supply voltage by electrical equipment such as static frequency converters, induction motors and arcing devices. Cycloconverters (which control large linear motors used in rolling mill, cement, and mining equipment), create some of the most significant interharmonic supply power problems. These devices transform the supply voltage into an AC voltage of a frequency lower or higher than that of the supply frequency.

Fig. 4: Sag

Fig. 7: Interharmonic Waveform

E. Undervoltages/ Sag

F. Swell/ Overvoltage

J. Notching

A swell is the increase in AC voltage for a duration of 0.5 cycles to 1 minutes time. High-impedance neutral

Notching is a periodic voltage disturbance caused by electronic devices, such as variable speed drives, light

Power Quality Problems: A Review  103

dimmers and arc welders under normal operation. This problem could be described as a transient impulse problem, but because the notches are periodic over each ½ cycle, notching is considered a waveform distortion problem.

Fig. 8: Notching

K. Noise Noise is unwanted voltage or current superimposed on the power system voltage or current waveform. Noise can be generated by power electronic devices, control circuits, arc welders, switching power supplies, radio transmitters and so on.

excessive heat to motor components, and the intermittent failure of motor controllers. Voltage unbalance can occur as a result of integration of a single phase DG, i.e., DG based on PV units, in DN. This unbalance becomes noticeable as more and more single phase DG units are introduced into DN. Imbalance can be estimated as the maximum deviation from the average of the three-phase voltages or currents, divided by the average of the threephase voltages or currents, expressed in percent. In equation form: voltage imbalance = 100 *(max deviation from average voltage)/average voltage TABLE 1: VARIOUS POWER QUALITY PROBLEM Power Quality Causes Problem TRASIENT–impulse Lightning, Turning major or oscillatory equipment on or off, Utility Switching Interruption

Fig. 9: Noise

L. Voltage Fluctuations

Sag

A Voltage fluctuation is a systematic variation of the voltage waveform or a series of random voltage changes, of small dimensions, namely 95 to 105% of nominal at a low frequency, generally below 25 Hz.

Swell Fig. 10: Fluctuation

M. Frequency Variations Frequency variation is extremely rare in stable utility power systems, especially interconnected systems.Frequency variation is more common especially if the generator is heavily loaded. Frequency variations may cause a motor to run inefficiently and/or additional heating and degradation of the motor due to increased motor speed and/or additional current drawn. This may be due to serious overloads on a network, or governor failures, though on an interconnected network, a single governor failure will not cause widespread disturbances of this nature.

Waveform Distortion DC off-set Harmonics, Interharmonics

Notching, Noise

Fig. 11: Frequency Variation

N. Voltage Imbalance/ Unbalance A voltage unbalance is when supplied voltages are not equal. These imbalances show as heating, especially with solid state motors. Greater imbalances may cause

Switching Operator, Attempting to isolate electrical problem and maintain power to power distribution area. Major equipment start up or shut down, Short circuits (faults), Undersized electrical wiring, Temporary voltage rise or drop, Excessive network loading, loss of generation, transformer taps set incorrectly High-impedance neutral connections, sudden (especially large) load reductions, and a singlephase fault on a threephase system

Effect Tripping, Processing Errors, dataloss, Burned circuit boards Equipment trips off, Programming is lost, Disk drive crashes. Memory loss, Data errors, Dim or bright lights, Shrinking display screens, Equipment shutdown

data errors, flickering of lights, degradation of electrical contacts, semiconductor damage in electronics, and insulation degradation

Overheating and saturation of transformers Electromagnetic Continuous interference from distortion of appliances, machines, normal voltage, radio and TV broadcasts Random data errors, visual flickering of displays and incandescent lights High-voltage lines, arcing data loss and data from operating disconnect transmission switches, startup of large problems, motors, radio and TV equipment stations, switched mode malfunction, power supplies, loads longterm with solid-state rectifiers, component failure, fluorescent lights, and hard disk failure, power electronic devices and distorted video displays. Table 1 (Contd.)…

104  International Conference on Recent Advances and Trends in Electrical Engineering (RATEE-2014) …Table 1 (Contd.) Voltage fluctuation(flicker)

Arc furnace, Voltage fluctuations on utility transmission and distribution systems

Intermittent Frequency variation