Lightning-Induced Overvoltage Peaks Considering Soil Parameters Frequency-Dependence and Multi-Layer Soils

Lightning-induced overvoltages are one of the main causes of distribution lines shutdown. Additionally, it is known that the soil resistivity highly impacts these induced voltages. Thus, this paper considers a recursive calculation to obtain an equivalent resistivity of any multi-layer structure considering the frequency-dependent electrical parameters of the soil in an approximate formula previously developed for the peak value of lightning-induced overvoltage in overhead lines. In addition, the suggested approach is more efficient regarding computation burden than conventional techniques since it estimates the overvoltage using equations instead of computing the lightning electromagnetic fields. This makes it a useful engineering tool that can be applied in practical situations. According to the results, it is possible to note the importance of using more than one layer of soil models that take into account the variation of soil parameters with frequency since overvoltage differences of up to 10 % when compared to independent soil parameters with frequency and equivalent resistivity of less than
$1000\ \Omega.\mathrm{m}$
.