Evaluation methods of polymer insulators under contaminated conditions

Although polymer insulators generally show superior insulation performance under contaminated and wetted conditions due to hydrophobicity on their surface, owing to shortage of their field experience, anti-contamination design criteria are not yet established. Presently the same design criteria for ceramic insulators are mostly adopted by considering the hydrophobicity as safety margin. In order to establish rationalized insulation design criteria for polymer insulators, the authors made a fundamental investigation. They found: (1) roughly two times heavier contaminant deposits on hydrophobic polymer insulators than porcelain under slow deposit conditions, while such differences become smaller under rapid deposit conditions like typhoon; (2) in spite of smaller leakage currents on hydrophobic polymer insulators, a stiff power source is still necessary for evaluating their contamination flashover voltages; and (3) contamination flashover voltages of hydrophobic polymer insulators should be evaluated under heavy wetting conditions. Combined tests under heavy fog and rain conditions may be good candidates for evaluating polymer insulators.