Frequency Dependence of Multilayer Soil Electrical Parameters: Effects on Ground Potential Rise

The paper presents a comprehensive study on the effect of frequency dependence of multilayer soil electrical parameters (SEPs) on ground potential rise (GPR). The lightning current has a large effect on the GPR. Typical analysis has often been based on quasistatic approximation that disregards the exact model of the grounding systems in the transient analysis of electrical networks, input impedance and GPR. To compute GPR in this paper, the full-wave approach based on the MoM solution to Maxwell equations is employed. To model the transient behavior of grounding systems, this method uses minimal approximations to find out GPR. The frequency dependence of SEPs combined with a multilayer soil are two complex issues that are modeled together. In the analysis of the GPR, special attention is given to the influences emanating from the soil multilayer structure and frequency dependency of SEPs. The GPR is calculated for three different soil configuration namely: 1) single layer, 2) two layer and 3) multilayer. From the simulations, the peak value of the GPR reduces when the frequency dependence of SEPs are taken into account. It is shown that considering the frequency dependent of multilayer SEPs can affect on the input impedance of grounding systems and GPR calculations.