Application of tower grounding device equivalent model in the calculation of transmission line back-flashover

The modelling of tower grounding device is the key for calculation of lightning strike response and lightning withstand level. In order to solve this problem, this study proposes a method to calculate the lightning response of transmission line grounding device by combining the advantages of CDEGS and EMTP software. Firstly, the authors calculate the frequency domain response of the tower grounding model in CDEGS; then the result is fitted according to modified vector fitting method to obtain the rational approximation expression of the impedance function. Furtherly, the corresponding equivalent circuits of tower grounding device is established in EMTP to realise accurate simulation of grounding device lightning strike response. The results show that the equivalent circuit model is more accurate than non-linear resistance model. Then, the factors that influence the lightning response and lightning withstand level are analysed based on the above method according to an actual transmission line model, which can provide reference for the lightning protection and grounding design.