Analysis of over-voltage protecting techniques applied to over-head insulated lines

To protect over-head insulated power distribution lines from surge over-voltage breakdown, even when a line conductor is melted down when lighting striking on the lines, nonlinear over-voltage protectors and low melting point discharge insulators are used as primary over-voltage protection techniques and have been widely applied in China for more than 5 years. The factual protecting effects of the two protection techniques were compared, discussed and analyzed in this paper based on their practical experiences including reliability, efficiency and safety. The research results approved that the number of line switch off and conductor melted down when lighting striking on the line was decreased greatly after these over-head insulated power lines installed with these over-voltage protecting equipments. Especially, the nonlinear over-voltage protector that recommended by the paper can restrain the surge over-voltage more effectively and shut off power frequency current flash more rapidly.