State of the art of semiconducting glazed insulators for transmission lines in heavily contaminated area

Semiconducting glazed insulators were developed long time ago. They, however, have been used in quite limited areas because of long-term reliability of performance was uncertain. Recent investigation results on our semiconducting glazed insulators applied in the field for 14 years showed good long-term performance without any failures. It was achieved by proper design of the insulators and improved material of semiconducting glaze. Good performance was verified by field and laboratory test results. Contamination withstand voltage was around 2-3 times higher than that of ordinary glazed insulators. In addition, the semiconducting glazed insulators could reduce corona discharge under contaminated conditions very much. Therefore, they can be applied for actual transmission lines and can make it possible to built compact lines.