Approximate Formula of Lightning-Induced Voltageson Distribution Lines considering a Wavefront DuIation of a Return Stroke Current

Abstract

This paper proposes an approximate formula of lightning-induced voltages on distribution lines considering a wavefront dulation of a return stroke current. Rusck's approximate formula has been used because its expression is very simple. However, Rusck's formula has enough accuracy only for a steepfront return stroke current with a slow velocity. Wavefront durations of natural lightning strokes are more than a few microseconds. Therefore, Rusck's formula has an error for a lightning surge analysis. Calculated results by the proposed formula agree well with those by a numerical analysis for various wavefornt durations and return stroke velocities. It is convenient to roughly evaluate overvoltages on distribution lines caused by an indirect lightning stroke by the use of a pocket computer.