Lightning Performance on Transmission Line Tower

Abstract

When a steep front lightning stroke current strikes the top of a transmission line tower, the tower top potential is influenced by the surge impedance of the tower, and there is a chance of a very high potential rise on the tower top during the round trip surge travel time along the tower. If such a voltage causes an inverse flashover of the string insulator of the phase conductor, a steep front surge voltage which has an extremely high crest does penetrate along the phase conductor. However, the lightning performance of a transmission line on the tower has not been investigated clearly for this steep front surge current, because the tower surge impedance and the performance of the string insulator in a very short time region has not been investigated satisfactorily. Recently, the author investigated the surge response of a transmission line tower and some equivalent circuits for the surge response of the tower have been obtained. The author estimated the lightning performance on transmission line towers by means of the tower equivalent circuit for a surge current together with an assumption in estimating the flashover characteristics of the string insulator.