A Simplified Method for the Evaluation of Lightning-Induced Overvoltage Peaks with Frequency-Dependent Soil Parameters

Indirect lightning strokes represent and important source of damage for overhead distribution systems. For the correct evaluation of lightning-induced overvoltages, the frequency dependence of the electrical parameters of the soil should be considered. Therefore, this paper proposes a simplified approach which selects a representative frequency according to the front time of the current waveform at the base of the lightning channel and takes advantage of an approximate formula for the lightning-induced overvoltage peak which is available in the literature. The most relevant strengths of the proposed method are the simplicity of implementation and the reduced process time, which is extremely lower than that required by more sophisticated numerical methods. These characteristics make the proposed approach a simple and practical tool. The results show overvoltage decreases above 35 percent for soils of low conductivity. Therefore, the frequency dependence of the electrical parameters of the soil plays an important role.