Lightning performance indices of overhead distribution lines

This paper describes to find out the lightning performance of 115 kV overhead distribution lines before and after to improve the lightning protection system for industrial by using EMTP (ATPDraw) Program and statistic data of lightning in Thailand. This program is used to analyze the lightning overvoltage. The indices are indicated the lightning protection which include shielding failure flashover rate, back flashover rate and total flashover rate. From the result of case study show that before improving the back flashover rate of several overhead distribution line arrangement schemes is very closely that to be 13-15 flashes per 100 km per year and after improving to be 9-13 flashes per 100 km per year.