Analysis of Lightning-Related Stress in Transmission Lines Considering Ionization and Frequency-Dependent Properties of the Soil in Grounding Systems

This article analyzes the performance of grounding systems buried in the ionized soil during the lightning discharge. To this aim, at first, a method to simultaneously analyze the transient response of grounding system considering the time-dependent nonlinear behavior arising from soil ionization and frequency dependence of soil electrical parameters related to the frequency content of the lightning surge is presented. The proposed method is performed by a combination of the harmonic balance method and the method of moment, which is aimed at representing an equivalent circuit to model the grounding system during the lightning discharge. The proposed model is validated by comparing the associated results with the published measurement and the numerical data for different grounding systems. Finally, an application of the proposed method is presented and the generated overvoltages across the insulator string caused by lightning strokes, the outage rates of transmission lines, and the lifetime of surge arresters are discussed.