Integration of Energy Balance of Soil Ionization in CIGRE Grounding Electrode Resistance Model

This paper proposes an improved CIGRE grounding electrode resistance model by integrating the energy balance of soil ionization. The main contribution of the improved CIGRE model is its accuracy to compute the time-dependent grounding electrode resistance under impulse condition. In addition, it can obtain correct resistance–current relation (hysteresis characteristic) of the grounding electrode. The accuracy of the improved CIGRE model is achieved by taking into account the effect of the arc resistance in soil, considering the energy balance of the soil ionization. The improved CIGRE model was validated for low resistivity soils ranging from 40 to 370 Ω·m. The comparison of the computed grounding electrode resistance obtained from the improved CIGRE model and experiment confirms the increase in the accuracy of the resistance and voltage response of the grounding electrode. The grounding electrode resistances obtained from the improved CIGRE model and experiments at current peak and current half value at decaying period (tail) have shown maximum differences of 3.5 and 2%, respectively. Moreover, precise voltage responses of grounding electrodes compared with the experimental results were obtained under different impulse currents.