An optimized transmission line model of grounding electrodes under lightning currents

In this paper, an optimized transmission line model (OTL) for modeling transient behavior of grounding electrodes under lightning currents is presented. The soil ionization effect is considered in OTL, and all electromagnetic couplings between different parts of grounding electrode are also considered by selecting the size of segment conductor properly and calculating the mutual coupling parameters between segment conductors accurately. Comparing with the traditional transmission line model, the optimized model can be used to accurately predict the effective length and transient potential rise (TPR) of grounding electrodes. Transient behaviors of grounding electrodes are simulated by OTL and the results are in good agreement with those of the electromagnetic model proposed by Grcev, and experiment results performed by Electricité de France and Geri. Furthermore, non-uniform discharging phenomenon of grounding electrode under lightning current is discussed, and the effective lengths of horizontal grounding electrode under lightning currents are presented.