Study and Analysis of Switching Transients in Power Distribution System

Abstract

The switching transient is not a new phenomenon; it has been around for many decades. However, it has received more attention recently because of the greater number of failure of many electrical equipments like transformer, circuit breaker etc. because of the phenomena. Both energization and de-energization of transformer and shunt capacitor bank produce considerable amount of transient overvoltage which in turn can cause insulation failure of transformer and malfunctioning of protective equipments. The worst case occurs if the frequency of the transients matches the resonance frequency of the transformer causing voltage and current magnification to a level that exceeds the BIL of transformer. The purpose of this thesis work is to study the switching transient over-voltages that occur during different switching events in an arbitrary distribution network. We have analysed the network for switching actions like switching of transformer, capacitor bank and switching of load. The analysis is done considering both overhead lines and underground cables to make a comparative study. Transient short circuit fault also causes high frequency overvoltage; which is analysed in this work. Finally, the analyses of the output data is done to find out the main reasons for this transient and some recommendations are given to minimize the effects of transient overvoltage.