Effects of asymmetrical algal distribution on the AC flashover characteristics of bio-contaminated silicone rubber insulators

Abstract Polymer insulators are reported to be contaminated by algae in tropical and subtropical climates around the world. Here, the biological contaminates were sectorial distributed on the insulator surface, stretching from the edge of the shed to the interior section near the core. The radial growth ratio and axial length of the algal column was varying under different environmental conditions. To explore the flashover characteristics under these conditions, the triangle plate model was established, in which algal colonization varied in radial growth ratio and algal column length quantitatively, and the inorganic pollutants were divided into three pollution degrees. The results showed that the increasing algal distribution gradually decreased the flashover voltage, whereas when the algal column was too slender, the flashover voltage increased. Meanwhile, the arc tended to elongate within the bio-contaminated area, and the flashover voltage significantly decreased when the algal column nearly covered the full specimen. Furthermore, surface conductivity and pollutant resistance were theoretically deduced from the Obenaus model, the results of which coincided with the calculated value from the flashover measurements. The change in discharge characteristics was attributed to the loss of hydrophobicity. This research could provide valuable information for the maintenance of bio-contaminated insulators in transmission lines of power systems.