Peaks of return strokes and fast pulses on ICC of winter lightning initiated by upward propagating leaders in Japan

Abstract

The authors have carried out measurement of the current waveforms associated with lightning discharges to wind turbines at Nikaho near the coast of the Sea of Japan since 2013. In this paper measured waveforms in winter up to 2020 are investigated and the current waveforms associated with return strokes after the extinction of the ICC (initial continuous current) and fast pulses superimposed on the ICC with the current peak of 2 kA or higher and with the risetimes of 8 µs or shorter are studied. The median current peaks of the 107 return strokes and the 123 fast pulses were 6.4 kA and 3.0 kA, respectively. The observed median current peaks of return strokes and fast pulses at the Nikaho wind turbines (6.4 kA and 3.0 kA) do not show much difference from those observed at the Gaisberg tower (9.2 kA and 4.2 kA), the Säntis tower (8 kA and 3.4 kA) and the Peissenberg tower in Germany (return stroke: 8.5 kA but no report on fast pulses) when the long sampling interval and the low upper cutoff frequency of the measuring system at the Nikaho wind turbines is taken into account.