Discussion of CIGRE current-dependent grounding resistance model

The soil ionization is an important factor for lightning surge analysis in electric power system. Many current-dependent grounding resistance models have been proposed. The CIGRE model is very simple, and is frequently used in lightning surge analysis. However, the model is not applicable to a large grounding electrode such as a grounding net and a tower-footing base because the model is derived by approximating a soil ionization zone to a hemisphere. This paper discusses the CIGRE model used in EHV transmission line surge analysis.