Estimation of critical electric field of soil ionisation based on tangential electric field method

The critical electric field of soil ionisation is very important for the performance of grounding system and spatial distribution of electromagnetic field in the soil when lightning directly strikes the lightning protection system. To estimate the critical electric field in the soil, a tangential electric field method is proposed based on the electromagnetic field analysis presented in this study. With this method, the instant moment when the soil ionisation occurs is obtained by examining the tangential component of horizontal electric field. According to the maximum electric field in soil without soil ionisation for every moment, the soil critical electric field could be estimated. In addition, the critical electric fields for four different types of soil reported in the literature are estimated with the tangential electric field method, yielding satisfactory agreement.