Lightning Performance Assessment to Improve Lightning Protection System of 115 kV Overhead Lines

Abstract

This paper determined suitable lightning performance indices for a lightning protection system of 115 kV overhead distribution lines for the cases before and after improvement with seven types of line configuration, following the construction standard of the Provincial Electricity Authority (PEA). The shielding failure flashover rate (SFFR) caused by a lightning strike to the line phase due to shielding failure, the back flashover rate (BFR) due to a direct strike on an overhead ground wire, and the total flashover rate(TFR) were used as lightning performance indices. The outage rate caused by lightning could be reduced by lightning performance improvement. This paper considered improvement and flashover rate analysis from lightning using five methods: reducing footing resistance, increasing the number of suspension insulators, increasing the diameter of the down conductor, reducing the shielding angle and installing a surge arrester on the lowest phase conductor. The analysis showed that before the improvements were implemented, the total flashover rate of several overhead distribution line arrangements was about 13-15 flashes/100 km/year and after the improvements were implemented, it was reduced to about 4-13 flashes/100 km/year.