Nodal frequency analysis of grounding systems considering the soilionization effect

Soil ionization takes place when the current leaking into the earth is high enough to produce an electric field intensity greater than a critical value. This phenomenon lowers the ground impedance and it is similar to an apparent increase in the electrode dimensions. Soil ionization has a great influence on the performance of small grounding electrodes fed by currents of high magnitude (i.e., lightning waves). In this paper, a new way of including the nonlinear soil ionization in the grounding system analysis is proposed. The study of the grounding system is performed in the frequency domain by means of an equivalent electric circuit