Direct Lightning Performance Assessment of Distribution Lines Considering Degradation of Insulation Strength owing to Salt Pollution

Abstract:
Many studies have shown that for well-protected medium voltage (MV) distribution lines, lightning faults associated with indirect lightning are less frequent and the lightning performance of these lines is determined by direct lightning. This paper evaluates the direct lightning performance of MV distribution lines with multi-point grounded shield wire and closeinterval surge arresters over lossy soil taking into account the degradation of insulation strength owing to salt pollution. Firstly, the flashover characteristics of the insulator considering salt pollution were investigated and a flashover model based on the integration method was developed. Then, the flashover rate owing to direct lightning was evaluated using the Monte Carlo procedure. The calculation results clarified that the influence of salt pollution on the flashover rate is relatively greater for the well-protected lines and soils with lower resistivity.