Modeling the Effect of Soil Ionization on Grounding System Dynamics during Transient Events

In this paper transient analysis of grounding systems is presented under lightning discharge on high voltage substation. Earthing grid, horizontal and vertical grounding electrodes buried in high resistivity soil are adopted in this study. Transmission line modeling (TLM) is adopted for modelling of grounding electrodes. This model can also be used to incorporate frequency dependent soil parameters. The soil ionization phenomenon is considered with non-linear conductance as a time varying function. Considered grounding models are subjected to high-magnitude lightning current impulses as a function of time. Transient voltage for all considered structures of grounding electrodes is calculated. Soil model with its parameters depending on frequency are also considered to improve the efficacy of proposed work. Obtained results are validated from published research outcomes in literature and satisfactory results are found. For the text case, vertical rod, horizontal electrode and different size of grounding grids are considered and transient voltages are simulated.