Statistical Characterization of Lightning Induced Overvoltage Waveforms in Overhead Lines

The proper insulation coordination of power apparatuses requires the knowledge of the withstand capability of the insulation against overvoltages stressing the given apparatus. By using a multivariate Monte Carlo procedure and the parameter probability distributions of the Cigré waveforms of the lightning current at the channel base, we provide a characterization of the parameter distributions of the induced voltage waveforms in a single conductor overhead line. A simplified formula is proposed to reproduce the curve that represents the expected annual number of lightning that induce voltages larger than the insulation level of the line in case insulators flashovers are not considered in the appraisal. The results for the case of an ideal insulation level are compared to those obtained by considering the flashovers in medium voltage insulators represented by means of the disruptive effect (DE) criterion. The parameters of the DE model are estimated by using the voltage-time-to-breakdown curve inferred from laboratory test results.