Investigation on Aging Characteristics of Anti-pollution Flashover Coating under AC Voltage

Room temperature vulcanized (RTV) silicone rubber coating has excellent hydrophobic performance and anti-pollution flashover characteristics, widely used in various high-voltage power equipment in China's power system. However, the insulation performance of RTV coating decreases rapidly due to aging and failure caused by long-term physical and chemical effects such as electric heating and ultraviolet. In this paper, the AC samples of RTV coating in Ningxia power grid were selected for a series of tests. The aging characteristics of RTV coatings with different years were analyzed from the aspects of sample appearance inspection, hydrophobicity, Fourier transform infrared spectroscopy (FTIR) and scanning electron microscopy (SEM). The results showed that RTV coating of in Ningxia power grid operates well, and hydrophobicity of the coating surface is remained in HC1~ HC2 level, which meets the requirements of equipment anti-pollution performance. Through FTIR and SEM analysis, it was found that the change of peak area of characteristic functional groups on the inner and outer surfaces is related to the migration of small molecules in the RTV coating, and the cracking of main chain functional groups was the main reason for the aging of RTV coating. Moreover, small molecular substances are easy to enter and stay in the coating due to the rough surface of RTV coating and the heavy pollution characteristics in Ningxia, which increasing the hydrophobicity of the coating surface. The research results will provide a scientific basis for the aging mechanism and insulation performance evaluation of AC anti-pollution flashover coating in Ningxia power grid.