Estimation of lightning overvoltages and critical flashover currents of 150 kV and 400 kV overhead lines: Effects of the CIGRE lightning current waveform parameters

Abstract

This paper investigates the influence of the CIGRE lightning current waveform parameters on the computation of fast-front overvoltages and critical lightning currents causing flashover of overhead transmission line insulation. The investigation is conducted via ATP-EMTP simulations employing both negative and positive lightning current waveforms corresponding to first return strokes. Typical 150 kV and 400 kV double-circuit overhead lines are evaluated by performing shielding failure and backflashover simulations. The statistical distributions of the parameters required as input for the CIGRE lightning current waveform (front time, maximum steepness, time to half value) are considered in simulations to quantify and analyze their effects; this enables the comparison between negative and positive lightning strikes. The waveform parameters do not affect considerably the critical shielding failure flashover current for both polarities; the most influential parameter in this case is the time to half value. On the other hand, the wavetail duration influences the least the critical backflashover current; the latter is lower for waveforms with faster wavefront (lower front time and higher maximum steepness). The impact of the waveform parameters of positive lightning strikes is more marked for the backflashover case due to their larger variations compared with negative strikes.