Evaluation in laboratory of nonceramic insulators having different leakage distance

Several 115 kV nonceramic insulators from the same manufacturer having different leakage distances and profiles were evaluated in a fog chamber. The material of the housing was the same for all the insulators. Repetitive cycles of dry, clean fog, and salt fog were applied to the insulators over a period of 1400 h of testing. The test voltage was 69 kV from phase to earth. Before starting the testing, each insulator was polluted with kaolin by the solid layer method and left out to dry. Every time that the magnitude of the leakage current got down, the insulators were polluted again, and the testing was continued. The specific creepage distances of the evaluated insulators were 20, 25, 31 and 39 mm/kV, according to IEC 60815. The leakage current was monitored continuously in order to know the frequency of peak leakage current on each insulator. Based on such value of frequency and shape factor, the performance of each insulator as a function of its leakage distance was analyzed. The obtained results show that the nonceramic insulators of 31 mm/kV and 20 mm/kV had better performance than those 39 mm/kV and 25 mm/kV, respectively, among the tested insulators. It is considered that the above performance may be related to the insulator profile.