Influence of Grounding Resistance of Surge Arrester on Direct Lightning Performance of Distribution Lines over Lossy Ground Considering LEMP Impact

Using electromagnetic transient (EMT) analysis, previous studies have shown that the outage rate of medium voltage (MV) distribution lines due to direct lightning strikes can be sufficiently reduced by the combined use of a shield wire and surge arresters installed at relatively close intervals, regardless of the grounding resistance (GR) of surge arresters. Although this finding was based on conventional EMT analysis, recent studies have shown the impact of lightning electromagnetic pulses (LEMPs) on overvoltages generated even by direct lightning strikes on MV distribution lines. Hence, using the LEMP-incorporated EMT analysis method, we analyzed the influence of the surge arrester interval, GR of surge arresters, and soil resistivity on the direct-lightning outage rate of MV distribution lines with a shield wire. Our analysis clarified that the lightning outage rate does not depend on the GR of surge arresters even when LEMP impact is considered; this trend was derived for a wide range of soil resistivities. Therefore, the combined use of a shield wire and surge arresters installed at relatively close intervals is an effective measure to reduce the direct-lightning outage rate of MV distribution lines.