On the application of frequency dependent soil models to the transient analysis of grounding electrodes

We present a comparison of six models representing the frequency dependence of soil electrical conductivity and permittivity, applied to the analysis of a horizontal grounding electrode subjected to typical first and subsequent lightning return stroke current. A full-wave computational model is adopted for the analysis, which is based on the antenna theory. It is shown that models by Scott, Smith-Longmire, Messier and Visacro-Alipio predict similar values for the peak value and the zero-to-peak time of the potential. On the other hand, the models by Portela and Visacro-Portela predict a significantly lower peak potential and a longer zero-to-peak time.