Analysis of the correlation between the impedance value of line surge arresters' grounding electrode and the withstand lightning voltage of insulator strings under shielding failure

Abstract

The current operation of high-voltage transmission lines falls short of achieving the desired level of lightning protection through the mere installation of a substantial number of zinc oxide surge arresters. In order to address this challenge, the conventional design approach involves validating the insulation coordination margin of both surge arresters and insulator strings under lightning impulses. However, this method still proves inadequate in establishing effective safeguards against flashovers and tripping. This study takes a departure point from the discharge pathway of surge arresters, analyzing the trajectory of lightning currents and the impact of the line tower's equivalent inductance on the cumulative voltage across insulator strings. It is revealed that the potential, which elevates due to wave impedance during surge arrester grounding, plays a pivotal role in withstanding overvoltage in insulator strings. The study introduces measures involving waveguide cables to mitigate residual voltage at tower poles. By modifying tower wave impedance values, the shielding failure lightning-induced tripping rate of power transmission lines can be effectively curtailed.