Comprehensive Modeling of Grounding Electrodes Buried in Ionized Soil Based on MoM-HBM Approach

This paper presents a new approach for modelling grounding electrodes buried in two layers soils considering frequency-dependent modeling of soil parameters together with the time-dependent nonlinear behavior arising from soil ionization caused by a lightning current discharge through the grounding system. To this aim, in the absence of soil ionization, a Norton's equivalent circuit is extracted in the frequency domain by means of the method of moment. Then, by adding the nonlinear load representing soil ionization to the Norton's equivalent circuit, the grounding system is changed into a nonlinear Norton's equivalent circuit and treated by using the harmonic balance method. The proposed model is validated by comparing the associated results with published measurement and the numerical data obtained with low- and high-magnitude impulse currents. The results prove that the proposed method is reliable and effective. Finally, an application of the proposed method in predicting the lightning overvoltages across the insulator string is presented and the performance of grounding system for different parameters is discussed.