Abstract
Recent lightning protection design has been considered against not only induced overvoltages due to nearby lightning hits, but also overvoltages due to lightning direct hits on power distribution lines.Electric power companies are both expanding conventional protection methods such as overhead grounding wire and surge arresters, and developing new protection equipments with a Zinc-Oxide surge divider.In order to get effective protection method, it is important to study the relation between protection method and lightning outage ratio of a power distribution system.From the above point of view, authors developed the program which can calculate lightning outage ratio due to both lightning direct hits and indirect lightning hits. Moreover this program can consider interval of lightning protection equipment, grounding resistance, flashover voltage of the insulator, and characteristics of surge arresters at will. In this paper, detail of the developed program and comparison of calculated outage ratio according to lightning protection methods are described.
