Electrified droplet on corona-charged surface of silicone rubber/SiO2 nanocomposite

In HVDC transmission lines, corona could occur even on well designed hardware and insulators, which can significantly damage the polymeric insulators and inject the charge in the surface of insulators. Rain formed by cloud elements may be highly electrified and a mixture of positive and negative drops is usually produced. Once the charged droplet is deposited on the surface, insulation performance of the insulators will be affected. In this research, the characteristic of an electrified droplet on coronacharged silicone rubber nanocomposite surface was observed under dc voltage stress. The samples were made by dispersing nano-scale SiO₂ powdered in silicone rubber with the weight ratios of 0, 1, 2, 3 wt%, and were charged for 5 minutes under a dc corona discharge system based on needle-plate electrode before the test. Then the flashover test was carried out under a dc stress between two aluminum plate electrodes. The effect of nano-silica weight percent on the surface charge density and the surface charge on contact angle was obtained. Electric field strength simulation was performed to analyze the effect on charged droplets and surface charge. The relationships among the charge density, the contact angle, and the flashover voltage via the droplet were obtained. The results show that charged droplet deposited on charged surface has a negative effect on the nano filled silicone rubber composites that can make the flashover occurs at lower voltage.