Evaluation of Improved Lightning Stroke Current Waveform Using Advanced Statistical Method

The peak current amplitude and front duration of lightning stroke current waveforms have conventionally been evaluated independently, and severe waveform assumptions are usually adopted in the current of lightning insulation designs. If lightning stroke waveform conditions are optimized, lightning insulation specifications of power facilities can be further rationalized. This paper proposes a new statistical technique to better evaluate lightning stroke current waveforms. The characteristics of lightning stroke current waveforms (i.e., that peak amplitudes correlate with front durations) are taken into account in this technique. The proposed technique was validated with various statistical tests. The front duration currently used in the design of the ultra-high-voltage system in Japan is 1.0 mus, but the potentially more accurate value of 1.7 mus was found when waveforms were evaluated with the proposed technique, and overvoltage analyses of gas-insulated switchgear show that overvoltages decrease with longer front duration.