Grounding Systems Transient with Frequency Dependent Soil Parameters: A Time Domain Approach

This study focuses on examining the transient behavior of grounding systems when subjected to the effects of lightning discharges. This research delves into examining the performance of vertical rods, horizontal conductors, and grounding grids with vertical grounding rods positioned at corners and buried within a two-layer soil structure. Transmission line modeling (TLM) is adopted with non-linear conductance phenomenon for modeling of grounding systems. Developed model deals with frequency-dependent soil parameters to study the transient behavior. The ionization phenomenon of soil is taken up by considering the non-linear conductance as a function of time and presence of residual resistivity. Grounding models are subjected to low and high-magnitude lightning current impulses with different rise time. Ground potential rise, grounding system's transient and impulse impedance are calculated to analyze the grounding performance. Apparent and effective diameter of the grounding electrodes are considered in the study that improves the accuracy of proposed work. For validation, obtained results are compared with measured results taken from the published literature and good agreements are found. The study further details the relationship between the effective length of grounding conductors during transient phases and variables such as soil resistivity and the rise time of lightning currents injected at various points along the conductor length.