Impact of Frequency-Dependent Soil on Transient Ground Potential Rise of Counterpoise Electrodes

Tower-footing grounding impedance has a fundamental impact on the generated overvoltages in power system when a transmission tower is hit by lightning. In order to compute accurately the tower-footing grounding impedance, the frequency dependence of soil electrical parameters (resistivity ρ
g
and relative permittivity ε
r
) must be considered in the simulations. In this paper, a comparative analysis on the transient Ground Potential Rise (GPR) generated by a lightning subsequent return stroke buried into the frequency-independent (FI) and frequency-dependent (FD) soils is carried out. Results show a significant reduction in the voltage peaks of the generated GPR waveforms when a FD soil model is assumed for the simulations.