Insights on the relevance of subsequent return strokes on lightning-related outages of Transmission Lines

Abstract:
The relevance of subsequent return strokes for the occurrence of backflashover in transmission lines was assessed. In spite of their median peak current about three times smaller than that of first return strokes, the maximum peak of their overvoltages across insulator are comparable and even higher than those of first return strokes, overall due to their much larger voltage drop along the tower. On the other hand, their contribution to the probability of backflashover remains very low (about only 10%). The traditional practice of disregarding their effect in the procedures for assessing the lightning performance of lines, using a slightly conservative flash density, seems a reasonable approach.