An Improved Circuit-Based Grounding Electrode Considering Frequency Dependence of Soil Parameters

This paper presents the simulation of circuit-based vertically oriented grounding electrodes with the consideration of frequency dependence of soil resistivity and permittivity. The resistivity and permittivity were determined using equations proposed by Sundae and Dwight and the frequency dependence properties were modelled according to Scott‘s model. It was found that the voltage response was highly affected by the frequency, especially at high soil resistivity of 1000 $\Omega{m}$ and above (up to 4% decrease in voltage response). As for the low soil resistivity cases, the voltage response was less affected by the frequency, which is 1.4% and 1% lower for soil resistivity of 100 $\Omega{m}$ and 10 $\Omega{m}$ respectively. Obviously, the current circuit-based model (frequency independent model) tends to provide overestimated results. Therefore, the effect of frequency on the soil resistivity and relative permittivity should not be neglected when determining the transient performance of grounding electrode in order to obtain accurate results.