Frequency Characters of Leakage Current on the Surface of Outdoor Insulators in Different Relative Humidity

Contamination flashover is one of the most serious problems in power delivery system. Leakage current that flows over the surface of the contaminated insulators is considered the main causation of this problem and a lot of researches have been carried out to study the characters of it. But the relationships between leakage current characters and relative humidity are still not clear. In this paper, two typical cap and pin insulators were used in the artificial pollution tests that carried out in a relative humidity (RH) controllable chamber. Leakage current waveforms on the insulating surface were recorded during the tests. The characters of leakage current waveforms under different ESDD and relative humidity in both time and frequency domain were analyzed. In the results, the relationships between frequency characters, ESDD and RH were presented. A means of flashover prediction that based on the frequency characters of leakage current was discussed at last.