Pollution performance of dc insulators under operating conditions

In order to investigate the behavior of insulators in a natural operating environment, a full–scale insulator testing rack was constructed at the Sylmar DC Converter Station, southern terminal of the ±400 kV HVDC Pacific Intertie Strings of insulators have been under testing continuously for almost four years. The insulators are energized directly by the Pacific DC Intertie System voltage and are subject to identical operating conditions as insulators on the dc line. Surface leakage currents are continuously being monitored and the surface contaminants regularly sampled. In addition, meteorological conditions at the site are recorded. The nature of contamination and its rate of accumulation are also monitored on a regular basis. Relationships between surface leakage current and weather parameters are analyzed in order to arrive at some clues as to the electrical behavior of insulators.