Where the risk of accidental power-frequency energization is concerned, the safety ground has a short-circuit discharge duty determined by the configuration and parameters of the power system. Safety is thus assured by selecting a safety ground having a short-circuit safety rating which matches the duty imposed by the power system. Up to now, a similar matching for lightning currents has not been possible. This paper addresses this problem by: 1. Determining the lightning current rating of typical safety grounds. 2. Calculating the lightning current discharge duty of safety grounds in terms of the insulation level of the line and the distance from the location of the thunderstorm. The analysis shows that special precautions are needed when working on power lines of voltage classes above 360 kV.
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Mousa et al. (1986) studied this question.