Field aging investigation and filler precipitation analysis on RTV coated insulators in China

Room temperature vulcanized (RTV) silicone rubber is a type of anti-pollution flashover coating which has been widely used in China. Featuring good hydrophobicity and adhesive property, RTV coatings are applied to insulators to increase the pollution flashover voltage of insulator strings. However, compared with high temperature vulcanized (HTV) silicone rubber used in composite insulators, RTV coatings are less durable in field operation. In this paper, investigation and experiments were conducted on some RTV coated insulators from Shanxi province and Guangdong province respectively. All the insulators have been in operation for about 6 years and the RTV coatings applied are produced by the same manufacturer. It is found that the performances of RTV coated insulators in Shanxi province are much better than those in Guangdong province. Phenomena such as chalking, color fading and peeling off were observed on RTV coated insulators from Guangdong whereas only slight loss of adhesion property and hydrophobicity were observed on insulators from Shanxi province. Micro structural analysis and macro performance tests were conducted on different positions of collected insulators and it is concluded that operation environment, especially humidity, have great impact on the operation performance of RTV coated insulators.