Flashover Characteristic Of Silicone Rubber Insulator In Contaminated Environment

This paper focuses on the behavior of a water droplet placed on the surface of a polymer insulator under DC voltage. A slice of polymer insulator which was made by silicone rubber was used as the test sample. The water droplet was dropped at the center of sample surface between the electrodes. The conductance was adjusted by addition of solute from 1.072 mS/cm to 4.92 mS/cm. Dynamic behaviors were observed by a monocular video zoom microscope. With the increase of electric field, the droplet elongated. Effects of lapse time, volume and conductance of water droplets were studied.According to lots of simulating tests on the model sample, this paper studied the discharge characteristics when one water droplet was on the silicone rubber surface and analyzed the flashover process of the clean silicone rubber surface covered with condensing water. The results showed that the electric field was intensified at the interface between the water droplet, air and silicone rubber. The flashover voltage of the silicone rubber insulator decreased with the increasing the volume and the conductance of water droplets. And it also decreased with the increase of the water temperature.The ultrasonic vibration saline fog generator filled with saline solutions was employed to simulate the contaminated environment of saline fog. Effects of relative humidity and saline fog conductance on silicone rubber insulator under DC electric field were studied. The study demonstrated that under the applied voltage the leakage current declined with the lapse time, but it turned to be constant after 4 or 5 minutes, while under a low relative humidity the leakage current was almost unchanged. The relative humidity was shown to have a marked effect on the leakage current. The leakage current increased with the relative humidity rising. There was no obvious change of the leakage current with the increase of the conductance when the relative humidity was less than 60%. The leakage current increased with the increase of the conductance in the case of the relative humidity higher than 60%.