Composite insulators are the critical components of power transmission systems. 371 composite insulators with an operating duration between 3 and 22 years from the lines in high temperature and humidity regions were sampled. The material properties, mechanical properties, electrical properties and interface properties of these insulators were researched systematically. Moreover, 19 aging characteristic index were put forward to describe the aging conditions of insulators. We analyzed the correlation between the aging index and operating years, and corresponding aging mechanism was discussed in this paper. Meanwhile, according to the analysis results, we established lifespan prediction models based on physics and statistics respectively. The results showed: lifespan of the sampled insulators was determined by the thermal oxidation process of silicone rubber. Lifespan of the silicone rubber material was 14.6 years while the electrical lifespan of composite insulator was 18.9 years. With regard to the rest of the insulators in high-temperature and high-humidity regions, their remaining lifespan could be predicted in accordance with the mechanical load and Fourier translation infrared spectroscopy (FTIR) test results. In the end, we selected 20 insulators which had run for 14 years, and predicted their lifespan with the method mentioned in this article, the forecast error was 1 year.

Research on aging evaluation and remaining lifespan prediction of composite insulators in high temperature and humidity regions

As a type of common and critical component, composite insulators have played an important role in power transmission systems. In order to investigate the law of diminishing function as well as to provide the macro and micro analysis of the aging process of insulators, 391 composite insulators which have run for 3–22 years in hot and humid areas were selected. The testing results showed that the mechanical properties and the electrical erosion resistance of silicone rubber had decisive effect on the functional decline. The decline process of mechanical properties was equivalently simulated with hot-oxygen aging model. The damage in the backbone of silicone rubber caused by sunlight and electric field resulted in the migration of ATH filler, which could lead to the increase in porosity of material as well as the decrease in corrosion resistance. Based on the law of diminishing mechanical function of silicone rubber and the pollution flashover tests' results, we also made prediction lifespan of both silicone rubber material as well as composite insulators.

Aging characterization and lifespan prediction of silicone rubber material utilized for composite insulators in areas of atypical warmth and humidity

The sheath and the shed in China are made of high temperature vulcanized (HTV) silicone rubber. The ferric oxide powder is widely used as red colorant, and it cannot disperse uniformly in the rubber for the reason that the ferric oxide powder is inorganic. In the paper, adding way and the amount of the ferric oxide powder are changed in the specimen-making process. Through hot air aging test, the changes of the specimen's electrical performances, mechanical properties and microstructure are considered, so the influence of the colorant on the specimen's property under hot air environment has been discussed. The results show that color masterbatch which is made of ferric oxide in advance, added in the rubber mixing process can improve the dispersion of the ferric oxide in the rubber, so that the ferric oxide can help reduce degradation of performance due to thermal-oxidative-aging. The radicals which are produced in silicone rubber's aging process could be trapped by the iron ions, which can be oxidated by oxygen in the air soon, and the amount of iron ions are not changed before and after the reaction. Therefore, increasing the content of iron oxide has no significant effect to improve the heat aging performance of the silicone rubber.

Congzhen Xie

Papers

The impact of the colorants on the aging properties of HTV silicone rubber