Assessment of operational reliability of power distribution network in a part of Dhaka city

Abstract

in the modcrn world, the importance of uninterrupted supply of electricity cannot be overemphasized. Per cupil<!consumption of electricity is lUlivcrsaily adop!cd as a yardstick of the living standard of a nation. It is needle8s to argue that unintermptcd and reliable supply of electricity can significantly enhance our socioeconomic life. Thrce principal componcnt~ in a typical ele<:tric power supply system are (a) the generating plant (b) the transmission system and (c) the distribution nctwork. All ofthcsc components must function properly to ensure the quality of electricity supplied. The present study is concerned with the perlormance characteristics of the distribmion network in the context of reliability. The distribution network plays a vi!.'!l role in the lotal power system. This links the eonsumcrs and sells electricity produccd by the generating plants. A number of factors influence the smooth fllnctioning of the network system. Network structure, method of operation. fluctuation or voltage ami frequency, nature of protection system, maintenance management, organi/.ational structure etc. can be identified as the major factors. In this study attempt has been made to investigate the reliability of electricity in Kawran Bffi'.ar sub. station covering a part of Dhaka city. Appropriate reliability indices have been calculated using the data and information collected from the concerned persons and department,>. Reliability uf electricity, as conceived in consumers' point of view, is the total timc of the year during which electricity supply over the network i~available. The parameters concerning the reliability of , electricity can be the number of interruptions at the load poinl, duratiun of interruptions, and the number of consumers affected. The distribution netwurk under study having about 17 (seventeen) vulnerable elements is effectively a series system without any parallel facility. Failure of one or more of the elements in the system results in disruption of electricity ~upply of the selecled part. Data and information gathered from relcvant sourees for the year 2001 have been utilized to evaluate the expected failore rate of the - elements. These results have heen used to determine [he overall reliability of the system. The average outage durntion has been estimated to be about 38 hours in the year. This parameter for a developed country like France is only 0.82 hours. Failure rates for individual elements of the systcm have been evaluated and the rates for s\vitchgear, overhead line, underground cable, transfoffiler are unusually high compared to any developed nation. Though this study is confincd within a part of Dhaka, the scenario can be treated as represcntative for the whole of the city. The significant identifiable rem,ons behind this frustmling scenario of electricity sllpply arc poor maintenance, usc of low quality and nnn-standard materials and components, lack of tmining of the personnel, lack or commitment, unplanned gro"'th of the city etc. The situation can be improved if the abovc mentioned problems arc properly addressed and appropriate measures are taken. Effective management system including modem database system has to be implemented. Considering the enonnous loss due to interruptions in electricity supply, parallel network system may be advantageous. However, the benefit-cost analysis is essential prior to making such decisions for huge investment.