Insulator Contamination Monitoring Based on Its Hygroscopicity Under Unsaturated Humidity

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.