Abstract
This article presented the characteristics of the grounding electrodes in uniform and two layer soils when subjected to lightning including the impacts of soil ionization with frequency, soil resistivity, and permittivity variations. The critical breakdown field strength of two layer soils with different values of the reflection factors was presented. The transient probabilistic grounding potential rise and the transient impedances of the horizontal and vertical electrodes were investigated in uniform and two layer soils including the effect of soil ionization with frequency. Finally, the influences of resistivity and permittivity variations which have substantial impacts on the electric field at the occurrence of the soil ionization were considered. Moreover, transmission line approach (TL) with the aid of ATP has been used to compute the transient grounding voltages. The results indicated that the reflection factor has a significant impact on the equivalent radius of the grounding electrode. It is also observed that the peak values of the lightning induced voltages decreases sharply when the soil ionization phenomenon considering the variations in soil resistivity and permittivity with the stroke frequency changes. Furthermore, the impedances of the burial electrodes that have negative reflection factors were lower than that in case of positive reflection factors.