Analysis of critical condition for dry and wet growth icing on insulators

Abstract

Icing on the insulators of transmission lines threats the safe operation of power system. Most of the existing researches focus on the discharge and flashover characteristics of ice-covered insulators. There is a lack of research on the growing process of insulator icing. In this paper, the critical condition for the dry and wet growth icing on insulators is taken as the research object. The calculation formulas of the freezing time of droplets and the collision interval time between adjacent water droplets are derived, based on which, the parametric characterization of different insulator icing types is proposed. By deriving the expression of the local collision efficiency β3, the distribution of water film on the insulator surface is obtained, which is used to distinguish the dry and wet growth icing on insulators. It is found that the critical condition of dry and wet growth icing is the condition that make the area covered with water film decrease to zero. With the decrease of temperature and droplets’ size, the area covered with water film decreases from the periphery of the droplet collision region to the centre, which is consistent to the observation test result on Xuefeng Mountain.