Estimation of Direct Lightning Flashover Rate of Medium Voltage Distribution lines under Salt Pollution Condition

Lightning performance assessment is important to carry out the effective lightning countermeasures for medium voltage distribution lines. And thus, many studies of indirect and direct lightning performance have been carried out. In many studies, the reduction of the flashover voltage due to salt pollution of distribution insulators has not been considered. When the insulator is polluted by salt, flashover voltage of the insulators decreases, and it may cause the increase of the flashover rate due to lightning. In this paper, at first, we show the flashover characteristics of insulators considering the salt pollution. Next, we estimate the direct lightning flashover rate under salt pollution condition by Monte Carlo procedure. The calculation results show that the influence of salt pollution on the flashover rate may be relatively greater in the well-protected distribution lines.