Development of Grounding Resistance Analysis Model of Rod Electrode Considering the Effect of Large-Current Characteristic for Distribution Lines

Grounding resistance is one of the important parameters in the lightning-protection design of electric power systems. The grounding resistance of electrode decreases as large currents are injected to the electrode by electric discharges in soil. This characteristic is not considered in lightning protection design. Therefore, the design level is kept on the exceeding level in actual phenomena. From viewpoint of the rational lightning protection design for the electric power systems, this characteristic should be considered in practical design. In this study, experiments were conducted using rod electrodes, and the physical phenomena of the electrical discharge in soil were considered by assuming a certain electrical discharge model in soil. Based on these results, a grounding resistance large-current characteristic analysis model that could be easily used in EMTP was developed.