Advanced observations of lightning induced voltage on power distribution lines. II

The authors discuss observations of induced voltages on the experimental overhead distribution line at a power plant facing the Japan Sea from October 1984 through March 1988. Waveforms of induced voltage from lightning strokes to a high stack of the power plant were measured simultaneously with the current waveforms of the lightning stroke to the stack. The polarity of lightning-induced voltage is opposite to that of lightning stroke current, regardless of the season. Except for unusual conditions, lightning induced voltages have a unipolar waveform. The lightning-induced voltage on the closest point of a distribution line to the lightning striking point is the maximum. The induced voltage waveforms generated on a distribution line were calculated by means of improved numerical analysis which took the height of the stack into consideration. The calculated results agree better with the measured waveforms than made those made by means of an earlier analysis method. It is clarified that bipolar induced voltages are not produced by usual lightning stroke currents