systems, neural networks, and genetic algorithms in power quality is included. ... Author Affiliation: Southern Illinois University. Abstract: .... resources in reliability cost/worth evaluation of distribution systems. ... This article proposes a new al-.
Discussion Deadline: January 2002
A Novel Software Implementation Concept for Power Quality Study Kezunovic, M.; Liao, Y. Author Affiliation: Texas A&M University, College Station, TX Abstract: A novel concept for power quality study is proposed. The concept integrates the power system modeling, classifying, and characterizing of power quality events, studying equipment sensitivity to the event disturbance and locating the point of event occurrence into one unified frame. Both Fourier and wavelet analyses are applied for extracting distinct features of various types of events as well as for characterizing the events. A new fuzzy expert system for classifying power quality events based on such features is presented with improved performance over previous neural network-based methods. A novel simulation method is outlined for evaluating the operating characteristics of the equipment during specific events. A software prototype implementing the concept has been developed in MATLAB. The voltage sag event is taken as an example for illustrating the analysis methods and software implementation issues. It is concluded that the proposed approach is feasible and promising for real world applications. Keywords: Power quality, pattern classification, signal processing, wavelet transforms. Preprint Order Number: PE-048PRD (8-2001) Discussion Deadline: January 2002
Artificial Intelligence and Advanced Mathematical Tools for Power Quality Applications: A Survey Anis Ibrahim, W.R.; Morcos, M.M. Author Affiliation: Kansas State University Abstract: Increasing interest in power quality has evolved in the past decade. This article surveys the literature for current applications of advanced artificial intelligence techniques in power quality. Applications of some advanced mathematical tools in general, and wavelet transform in particular, in power quality are also reviewed. An extensive collection of literature covering applications of fuzzy logic, expert systems, neural networks, and genetic algorithms in power quality is included. Literature exposing the use of wavelets in power quality analysis as well as data compression is also cited. Keywords: Power quality, artificial intelligence, fuzzy logic, expert systems, neural networks, genetic algorithms, wavelets, data compression. Preprint Order Number: PE-818PRD (8-2001) Discussion Deadline: January 2002
Wavelet and Wavelet Packet Compression of Power System Disturbances Hamid E.Y., Kawasaki, Z.-I Author Affiliation: Osaka University, Osaka, Japan Abstract: This article introduces a compression technique for power disturbance data via discrete wavelet transform (DWT) and wavelet packet transform (WPT). The data compression leads to a potential application for remote power protection and power quality monitoring. The compression technique is performed through signal decomposition up to a certain level, thresholding of wavelet coefficients, and signal reconstruction. The choice of which wavelet to use for the compression is of critical importance, because the wavelet affects reconstructed signal quality and the design of the system as a whole. The minimum description length (MDL) criterion is proposed for the selection of an appropriate wavelet filter. This criterion permits to select not only the suitable wavelet filter but also the best number of wavelet retained coefficients for signal reconstruction. The experimental study has been carried out for a single-phase to ground fault event, and the data compression results of using the suitable wavelet filter show that the compression ratios are less than 11% and are reduced to 62
more than a half of that percentage value by implementing an additional lossless coding. Keywords: Data compression, power disturbances, wavelets, wavelet packets. Preprint Order Number: PE-665PRD (8-2001) Discussion Deadline: January 2002
A Simplified Dynamic Model of Grid-Connected Fuel-Cell Generators Hatziadoniu, C.; Lobo, A.; Pourboghrat, F.; Daneshdoost, M. Author Affiliation: Southern Illinois University Abstract: This article describes a reduced-order dynamic model for a grid-connected fuel-cell power plant that is suitable for preliminary stability assessment. Generic voltage and power control loops are included. The model is applied to a distributed utility that uses fuel cells and gas turbines to investigate the nature and magnitude of their interaction. The studies presented in the paper show the effect of the mix between fuel cell and gas turbine generation on the system stability. The developed model, being simple, could provide a useful tool for the planning of distributed generation. Keywords: Fuel cells, distributed generation, dynamic stability, system planning. Preprint Order Number: PE-785PRD (8-2001) Discussion Deadline: January 2002
Behavior of Induction Motor Protection Due to Voltage Sags and Short Interruptions Gomez, J.C.; Morcos, M.M.; Reineri, C.A.; Campetelli, G.N. Author Affiliation: National University of Rio Cuarto; Kansas State University Abstract: An experimental study and some calculations on induc-
tion motor behavior were carried out. The effects due to short interruptions and voltage sags were investigated. A standard three-phase squirrel-cage motor of 5.5 kW, 1500 rpm, 380 V was used. The presence of induction motor changes the voltage sag waveform and duration. Protection characteristic curves and contactor ride-through capability together with their improvement are also studied. The interaction between motor load, system hot-load pickup, and voltage sag magnitude determine the motor reacceleration duration and magnitudes. Besides, on-sag and post-sag currents can reach levels higher than the direct start values. Post-sag overcurrent duration can last more than twice the normal start time period, having specific energies in the same order of magnitude. Keywords: Hot-load pickup, induction motor, motor reacceleration, power quality, short interruptions, voltage sags. Preprint Order Number: PE-387PRD (8-2001) Discussion Deadline: January 2002
Phase-to-Ground and Phase-to-Phase Sparkover Characteristics of External Insulation at the Entrance of an UHV Substation Yamagata, Y.; Oe, A.; Miyake, K.; Aihara, Y.; Shindo, T. Author Affiliation: Tokyo Electric Company; Central Research Institute of Electric Power Industry Abstract: For rational insulation design of an UHV substation, full-scale switching impulse tests of phase-to-ground (shielding ring-to-tower) and phase-to-phase (shielding ring-to-shielding ring) insulating clearance have been carried out in dry and wet conditions. In the tests, shielding rings that will be installed on bushings at actual UHV substations were used. The sparkover voltages depend on not only gap configurations but also the waveform of applied switching impulses; in other words, they show what we refer to as U-characteristics. Critical sparkover voltages are higher than those of rod-rod gaps by 20-25% in dry conditions and by 7-10% in wet conditions. Preprint Order Number: PE-378PRD (8-2001) IEEE Power Engineering Review, November 2001
Discussion Deadline: January 2002
Measurement of Network Harmonic
Impedences: Practical Implementation
Issues and Their Solutions Xu, W.; Ahmed, E.; Zhang, X.; Liu, X. Author Affiliation: University of Alberta Abstract: Determination of network harmonic impedances using pre- and post-disturbance steady-state waveforms is a well-known technique. Due to practical constraints, however, it is not quite straightforward to implement the technique for real-life applications. Using an actual utility case as an example, this paper presents practical implementation issues involved and their solutions. Improvements are made to the technique by applying 0 transformation on three-phase measurements. The usefulness of the improved technique is demonstrated with simulation and field measurement results. Since the technique only requires steady-state data, it can be easily implemented with many common power quality meters. One of the applications of the technique is to determine the existence of resonance conditions for shunt capacitor applications. Keywords: Harmonics, harmonic impedance and harmonic resonance. Preprint Order Number: PE-346PRD (8-2001) Discussion Deadline: January 2002
Reliability Cost/Worth Assessment of Distribution Systems Incorporating Time Varying Weather Conditions and Restoration Resources Wang, P.; Billinton, R. Author Affiliation: Nanyang Technological University; The University of Saskatchewan Abstract: This paper presents a time sequential simulation technique incorporating the effects of weather conditions and restoration resources in reliability cost/worth evaluation of distribution systems. Time varying weight factors (TVWF) are introduced to represent the effects on component failure rates and restoration times of weather and
available restoration resources. The average failure rate is combined with the TVWF to create time varying failure rates (TVFR) for each component. The average restoration time is combined with the TVWF to create time varying restoration times (TVRT). Studies conducted in a test distribution system show that the TVFR have large impacts on the interruption costs of frequency sensitive customers and slight effects on others. The TVRT have significant effects on the indices for all the customers. It is therefore important to consider TVRT in evaluating reliability cost/worth of network reinforcement. Keywords: Distribution systems, reliability cost/worth, network reinforcement. Preprint Order Number: PE-497PRD (8-2001) Discussion Deadline: January 2002
Feeder Switch Relocation for Customer Interruption Costs Minimization Teng, J.H.; Lu, C.N. Author Affiliation: I-Shou University; National Sun Yat-Sen University Abstract: Most electricity service interruptions are due to failures in the distribution network. In a competitive market, service quality and reliability have become an essential part of the business. In order to enhance the reliability in the distribution system, a value-based method is proposed in this article to take load distribution changes into account and search for new locations of feeder sectionalizers such that the customer interruption costs (CIC) can be reduced. Two stages are involved in the search. Using local information, the first stage determines the search direction, and in second stage, it decides whether a crossover of the load point is beneficial. To avoid being trapped in a local minimum, IEEE Power Engineering Review, November 2001
a mutation technique is also applied to look for the global optimum. Actual feeders were used in the tests and test results have shown that with a proper adjustment of the feeder sectionalizers, service reliability can be improved and the customer outage costs are reduced. Keyword: Distribution reliability, SAIDI, sectionalizer relocation, customer interruption cost, value-based planning. Preprint Order Number: PE-486PRD (8-2001) Discussion Deadline: January 2002
Sparse Network Equivalent Based on Time-Domain Fitting Boaventura, W.C.; Semlyen, A.; Iravani, M.R.; Lopes, A. Author Affiliation: Federal University of Minas Gerais; University of Toronto; University of Campinas Abstract: This article presents an approach for a network equivalent calculation for the analysis of electromagnetic transients in power systems. It is based on time-domain fitting and enforces some degree of sparsity while preserving the accuracy of the equivalent. The calculated equivalent is appropriate for direct interface with the rest of the system in time domain. A constrained least squares solution of the time-domain fitting equations is used to ensure accuracy at zero and 60 Hz. Results demonstrating the accuracy and computational efficiency of the method are presented. Keywords: Network equivalent, electromagnetic transients, time-domain fitting, discrete time, constrained least squares. Preprint Order Number: PE-079PRD (8-2001) Discussion Deadline: January 2002
Optimal Feeder Routing in Distribution System Planning Using Dynamic Programming Technique and GIS Facilities Boulaxis, N.G.; Papadopoulos, M.P. Author Affiliation: National Technical University of Athens Abstract: Optimal feeder routing is an important part of the general optimal distribution network planning. This article proposes a new algorithm for the optimal feeder routing problem using the dynamic programming technique and GIS facilities. All practical issues, such as cost parameters (investments, line losses, reliability) and technical constraints (voltage drop and thermal limits), as well as physical routing constraints (obstacles, high cost passages, existing line sections), are taken into consideration. The algorithm developed is validated comparing its results for a simplified study case with those obtained by an established solver. The effectiveness of the algorithm is further illustrated for a "real world" study case. Keywords: Planning, power distribution planning, routing, dynamic programming, geographic information systems. Preprint Order Number: PE-458PRD (8-2001) Discussion Deadline: January 2002
Power Disturbance Classifier Using a Rule-Based Method and Wavelet
Packet-Based Hidden Markov Model Chung, J.; Powers, EJ.; Grady, W.M.; Bhatt, S.C.
Author Affiliation: The University of Texas at Austin; EPRI Abstract: This article presents a novel classification method for power distribution line disturbances using a rule-based method and a wavelet packet-based hidden Markov model. The rule-based method is utilized for the classification of time-characterized-feature disturbances, and the wavelet packet-based hidden Markov model is utilized for the frequency characterized feature power disturbances. This proposed method classifies six types of actual recorded power distribution disturbances, i.e., sag, interruption, fast capacitor switching, capacitor switching, normal variation, and impulse disturbance, and obtains 98.7% correct classification rate for 670 actual disturbance events tested. 63
