Abdul-Rahman AI-Ali, Abdul Khaliq & Muhammad Arshad. School of Engineering ... 8-channel analog to digital converter (ADC) of the embedded system. The.
IEEE MELECON 2004, May 12-15,2004, Dubrovnik, Croatia
GSM-Based Distribution Transformer Monitoring System Abdul-Rahman AI-Ali, Abdul Khaliq & Muhammad Arshad School of Engineering, American University of Sharjah Box 26666, AUS, Sharjah, United Arab Emirates Email: {aali, akhaliq, marshad}@ausharjah.edu
Abstract - This paper presents design and implementation of a mobile embedded system to monitor and record key operation indictors of a distribution transformer like load currents, transformer oil and ambient temperatures. The proposed on-line monitoring system integrates a Global Service Mobile (GSM) Modem, with stand alone single chip microcontroller and sensor packages. It is installed at the distribution transformer site and the above mentioned parameters are recorded using the built-in 8-channel analog to digital converter (ADC) of the embedded system. The acquired parameters are processed and recorded in the system memory. If there is any abnormality or an emergency situation the system sends SMS (Short Message Service) messages to designated mobile telephones containing information about the abnormality according to some predefined instructions and policies that are stored on the embedded system EEPROM. Also, it sends SMS to a central database via the GSM modem for further processing. This mobile system will help the utilities to optimally utilize transformers and identify problems before any catastrophic failure.
I. INTRODUCTION Distribution Transformers have a long service life if they are operated under rated conditions. However, their life is significantly reduced if they are overloaded, resulting in unexpected failures and loss of supply to a large number of customers thus effecting system reliability. Overloading and ineffective cooling of transformers are the major causes of failure in distribution transformers. Most power companies use Supervisory Control and Data Acquisition (SCADA) system for online monitoring of power transformers but extending the SCADA system for online monitoring of distribution transformers is an expensive proposition. Distribution transformers are currently monitored manually where a person periodically visits a transformer site for maintenance and records parameter of importance. This type of monitoring can not provide information about occasional overloads and over heating of transformer oil and windings. All these factors can significantly reduce transformer life. A number of techniques are currently being used for offline as well as online monitoring of power transformers [I-61. Most power companies do online monitoring of their power transformers that involve Partial Discharge monitoring, recording their load conditions, gas-in-oil and moisture analysis etc. All these measurements provide
0-7803-827 1-4/04/$20.00 02004 IEEE
useful data for monitoring and diagnostics. Later this data is transmitted to the onsite or off-site control room via a dedicated communication link or SCADA system [2-41. However no work has been reported on the online monitoring of distribution transformer. Online monitoring of key operational parameters of distribution transformers can provide useful information about the health of transformers which will help the utilities to optimally use their transformers and keep the asset in operation for a longer period. This will also help identify problems before any catastrophic failure which can result in a significant cost savings and greater reliability. Widespread use of mobile networks and GSM devices such GSM modems and their decreasing costs have made them an attractive option not only for voice media but for other wide area network applications. This paper describes the design of a monitoring system that consists of a GSM modem that is integrated with stand alone single chip embedded system to monitor and record key operation indictors of a distribution transformer like load currents, transformer oil and ambient temperatures. The paper is organized as follows; section two discusses the proposed hardware architecture, the embedded software algorithm is described in section three and section four has the experimental results. Conclusion and future is worked discussed in section five. 11. HARDWARE ARCHITECTU~ The system hardware has four hardware modules as shown in Figure 1: embedded system, GSM modem, mobile-users and GSM networks and PC-based server. The embedded module is located at the transformer site. It is utilized to acquire, process, display, transmit and receive the parameters to/fiom the GSM modem. The second is the GSM module. It is the link between the embedded system and the public GSM network. The third is utility module that has a PC-based -server located at the utility control center. The server is attached to GSM modem and receivedtransmits SMS f r o d t o the transformer site via the GSM module. Detailed specifications and functions of each module are described as follows: Embedded system module has two blocks: Signal Conditioning Circuit (SCC) block and Controller block. The SCC block reads the currents, voltages, temperatures from sensors.
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