Study on the Impact of Contamination Containing High Proportions of Metals on the AC Flashover Characteristics of Insulators

In heavy metal industrial areas, the issue of insulation flashover caused by metal contamination on the external insulation of transmission lines has become increasingly prominent. This paper investigates the U160B/155 porcelain insulator, examining how iron, copper and zinc metal contaminations affect its AC flashover characteristics. Furthermore, combining with leakage current, the flashover mechanism of the insulators under the influence of metal particles is analysed. The research results indicate that as the metal content increases, the insulator's flashover gradient (E_L) decreases by up to 2.3%–17.2%. Different metal compositions exhibit consistent mechanisms, similarly impacting insulator's dielectric strength with copper showing slightly weaker effect. And then, based on the mechanism of metal particles' influence on the insulator's AC flashover, a formula for calculating E_L is proposed and the calculated results are basically consistent with the experimental conditions. Finally, different metal compositions have similar effects on the leakage current, with an increase in metal content leading to an increase in the critical leakage current, which gradually tends to saturation. The research findings of this paper can provide references for AC flashover prediction, assessment and prevention of external insulation in areas with metal contaminants in pollution sources.