Comprehensive Modeling of Transient Analysis of Grounding System under Lightning Surges

During lightning discharge, the transient performance of grounding system is influenced by the time-dependent nonlinear behavior related to soil ionization and frequency dependence of soil electrical parameters related to high-frequency spectrum of lightning current. In this paper, for the modeling of grounding system, a new approach based on the combination of the method of moment (MoM) and the harmonic balance method (HBM) has been used. In order to increase the accuracy, the phenomenon of soil ionization in the time domain and the effects of frequency dependence of soil electrical parameters in the frequency domain are considered simultaneously in the modeling. In the presented method, first by analyzing the ground system through solving integral equations with the method of moment (MoM), a Norton’s equivalent circuit is extracted in frequency domain assuming frequency dependent of soil electrical parameters. At this stage, the equivalent circuit is extracted in the absence of soil ionization. Then, by adding the nonlinear load arising from soil ionization to the Norton’s equivalent circuit, the grounding system is changed into a nonlinear Norton’s equivalent circuit. To analyze the obtained nonlinear circuit, the harmonic balance method (HBM) is used. The proposed model is validated by comparing our data with published experimental results. The obtained results confirm efficiency and accuracy of the proposed method.