Abstract
Grounding resistances of transmission towers in Japan are commonly required to be less than 10 ohm to avoid lightning back flashover accident. The surrounding soil, therefore, must be improved by chemical or construction ways if the resistance are much higher than the recommended value. In order to reduce the cost of these works, the authors have investigated on flashover simulation with various grounding conditions. In this paper, we propose the particular model for grounding resistance concerning the impulse characteristics of an actual 500 kV-transmission tower footing base. We also present the results of the EMTP simulations with the proposed model, where the results suggest that it be not always necessary to limit the grounding resistance less than 10 ohm and it may be possible to reduce construction cost for transmission towers.
