TRANSIENT OVERVOLTAGES DUE TO LIGHTNING

Abstract

Lightning strokes whether direct or• indirect are one of the important causes of outage of transmission lines. To provide optimal protection to an overhead line against lightning strokes, it is necessary to predict the severity of the transient overvoltages, generated by such strokes. In this dissertation an attempt has been made to calculate the transient overvoltage due to lightning strokes on the tower and analyse the propagation of transient overvoltages by using Electromagnetic transients program (EMTP). The various types of overvoltages that may arise on a transmission network are discussed in chapter - 1. And various methods or techniques for the calculation of transient overvoltages, namely field tests, analog and digital techniques, have been given in chapter - 2. Subsequently an indepth study of transient overvoltages due to lightning, by modelling the path of the lightning current ie:,.tower, transmission lines and ground wire, using electromagnetic transient program, has been made. Corona on the transmission line due to transient overvoltages produces additional attenuation. This attenuation has been taken into account by modelling corona.