Influence of crystallization effect during icing water phase transition on the flashover characteristics of ice-covered insulators

Abstract

The crystallization effect during the phase transition of icing water has a significant impact on the electrical performance of an ice-covered insulator. However, the spatial distribution of conductive ions in the ice layer remains poorly understood. In this study, the crystallization effect was confirmed through a condensation test of the potassium permanganate solution. The influence of freezing water conductivity, ice thickness and equivalent salt deposit density on the spatial distribution of conductive ions was determined by a triangular ice sample, wherein the effect on the flashover characteristics of ice-covered insulator was investigated. Results show that MnO−4 migrates to the unfrozen area during freezing, thus accumulating on the droplet top. The conductivity of melted water on the exterior surface of an ice sample is considerably higher than that of icing water. The former can reach a maximum of 5.7 times the latter when the freezing water conductivity method is adopted. This value is 9.7 for a polluted ice sample. A highly conductive water film forms on the insulator surface because of the crystallization effect in the melting period, thereby improving the leakage current and reducing the residual ice resistance, which results in the decrease of flashover voltage.