Observation of current waveshapes of lightning strokes on transmission towers

Considerable cost reductions have been achieved through rationalizing insul ation design for substation equipment based on the application of high-perf ormance surge arresters and improvement in analysis techniques. For further rationalization in insulation design and cost reduction, it is important t o evaluate the lightning stroke current waveshape in detail. Some studies t o observe current waveshapes have been conducted before, but they were ones conducted on independent towers and do not provide many data in a large-cu rrent region. So, we have been observing lightning stroke currents larger t han 9 kA on 60 transmission towers (mainly 500 kV lines) since 1994. In thi s paper, we present some lightning parameters for insulation design of subs tations, drawn from current waveshape data, which have been collected so fa r. In addition, we report on the relationships among the peak value, the fr ont steepness and the front duration, which heavily affect the insulation d esign of substations.