A pre-warning method of contamination flashover based on the leakage current of insulators in dry condition

摘要

The contamination flashover is a enormous threat to the safety of power transmission lines, and the pre-warning of flashover is of great significance. This paper investigated the leakage current of ceramic insulators under the dry and wet condition. To find a method for the early pre-warning of falshover, the waveform of leakage current under dry condition is compared with the one under wet condition. The experimental procedure was determined under the reference of IEC standard 60507. With the dry contamination layer, the leakage current over the insulater surface appears sine wave and show a great difference in the valid value when in heavy pollution and light pollution. Due to the lack of enough characteristics to realize the pre-warning, the frequence domain charateristics were analysed. The ratio between odd harmonic and fundamental wave was selected as the alert indicator. The waveform of leakage current was analyzed by the FFT method, and the THD of current under the wet condition is obviously larger than the dry condition. Under the dry condition, the ratio K13 and K15 appears distinct difference and the research can be applied to the pre-warning of contamination flashover.