Influence of grounding impedance model on lightning protection analysis of transmission system

• Different grounding impedance model leads to different simulated lightning withstand level.
• The lightning withstand level based on SDR model is larger than that based on RTDR model while the result based on CR model is the smallest.
• CR model is unreasonable while being applied in the lightning protection analysis.
• SRD model and RTDR model generate different dynamic resistance curves.
• SDR model ignores inductive effect and underrates the soil ionization effect, and RTDR model describe the transient performance of the grounding device better.

Lightning protection analysis is of vital importance for the transmission system, on which the grounding impedance model has a great effect. This paper concerns the influence of the grounding impedance model on lightning protection analysis. The transmission system is established in PSCAD/EMTP with consideration of three grounding impedance models as constant resistance, standard dynamic resistance and real-time dynamic resistance. The lightning withstand level is simulated and obtained under several typical conditions of soil resistivity and voltage levels. Moreover, the models are comparison and analyzed in the aspects of the dynamic resistance, as well as the ground potential rise and the insulator voltage. This makes a contribution for determining the suitable grounding impedance model applied in the lightning protection analysis, which is very meaningful both in theory and practice.

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