Analysis of the Polarity Effect of Lightning Arresters with Gaps and its Correlation with Wet Flashover Tripping of Insulators

Currently, the standard for the line surge arrester usually verifies its discharge characteristics by the 50% discharge voltage under positive lightning impulse. According to the gas discharge theory, the polarity of lightning impulse voltage significantly impacts the plate-plate gap breakdown voltage, whereas its impact on rod-rod gaps is comparatively minor. Consequently, for insulator string, its 50% lightning impulse discharge voltage and volt-second characteristics in different voltage polarities are not big differences. However, both the 50% discharge voltage under the negative lightning impulse and the volt-second characteristic curve of line surge arresters are notably higher than those of positive ones, which is mainly caused by the polarity effect of gas discharge. Therefore, in cases where the practical installation scenario of the surge arrester gaps is negative discharge voltage, the voltage value may surpass the wet flashover voltage value of the insulator strings, which can lead to surge arrester protection failure and subsequently result in line faults and tripping. To this end, the selection of the gap position of the surge arrester directly impacts the sensitivity of lightning protection provided by the surge arrester, which needs to be comprehensively analyzed and studied in theory and practice. In this paper, an installation mode of changing the gap position of the surge arrester to the cross arm of the tower is proposed, which can effectively improve the lightning protection effect.