Influence of grounding representation on the lightning performance of line surge arresters — Part I: Impact on the developed overvoltages

This paper, divided into two main parts, investigates the influence of considering or not the frequency-dependent characteristics of tower-footing grounding on the lightning performance of line surge arresters. The lightning performance of a surge arrester installed in a typical Brazilian 138-kV transmission line is assessed, while the tower-footing grounding system is modeled in two different ways namely: i) a static model, consisting of a lumped resistance with value equal to the low-frequency grounding resistance, and ii) a full-wave wideband model considering the frequency-dependent characteristics of grounding. Taking as reference the results determined using the wideband model, it is shown that the static model (lumped resistance) can lead to errors and incorrect predictions of insulation failure in lines partially protected by lightning surge arresters.