Lightning Performance of Transmission Lines: Impact of Current Waveform and Front-Time on Backflashover Occurrence

The influence of the return-stroke current waveform and front-time on the occurrence of transmission-line backflashover was assessed via numerical simulation, using the data of two real lines as examples. The overvoltages resulting from distinct lightning current representations (triangular, CIGRE-concave, and double-peaked waveforms) were calculated using an electromagnetic model. The occurrence of backflashover was assessed applying different flashover criteria. Using robust criteria, in particular, the disruptive effect and leader progression models, leads to similar backflashover probabilities for all waveforms; although the probability resulting from these criteria could be different. Also, it leads to practically the same probability obtained using the median current front-time (3.8 μs) or by varying this parameter within realistic range (1.5–10 μs). This still holds true when a correlation between the front-time and peak current is considered. The conclusions are not valid when applying the voltage–time curve method, as the results yielded by this flashover criterion are affected both by the current waveform and the front-time.