An efficient method to assess the indirect lightning performance of overhead lines

This paper presents an approximate formula for the evaluation of the peak value of lightning-induced voltages in overhead lines over lossy ground, which considers the front-time of the channel-base current. The formula is used in the assessment of indirect lightning performance of overhead power distribution lines, and its results are compared with results available in the literature. The formula is then used to analyze the influence of some parameters on the lightning performance of overhead lines. The results show that the front-time influence decreases as the soil resistivity increases, and that a higher front-time leads to a lower flashover rate. It is shown that the use of a fixed front-time T = 5.63 μs leads to results that matches well the results obtained from Cigré´s front-time probabilistic distribution. Regarding the return stroke velocity, the results show that, for soils with resistivity higher than 100 Ωm, the flashover rate increases as the return stroke velocity increases. The results also show that a relative velocity v_r = 0.4 leads to flashover rates that match well the results obtained considering some correlations between return stroke velocity and peak current proposed in the literature.