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Pollution flashover of transmission line insulator seriously affects the safe operation of the power system. The insulator contamination is mostly deposited in dry weather, while the existing leakage-current-based pollution warning models could only send out a warning signal at a saturated moisture level, which seldomly happens and would be late for the pollution warning for online insulators. To monitor the change of insulation pollution degree under unsaturated humidity, a new method based on the humidity change and insulator contamination wetting characteristics is proposed in this paper. It has been found that under 75%~99% relative humidity, with the change of atmospheric humidity, the water content of the contamination changes from an equilibrium value to another equilibrium value exponentially, resulting in a linear relationship between the leakage current and the relative humidity with a slope proportional to the insulator pollution degree. Therefore, the site pollution degree of insulators can be obtained by the minute measured value.
Cao et al. (Sat,) studied this question.