Influence of Moist Environment on Aging Performance of Energized Silicone Rubber Used for Outdoor Insulation

The influence of moist environments on the aging performance of silicone rubber (SR) used for outdoor insulation was investigated by a salt-fog test. High-temperature vulcanized (HTV) SRs with different alumina trihydrate (ATH) filler contents were adopted as the test specimens. For the test of a single water droplet, the vibration and elongation of the water droplet caused a flashover, and the flashover voltage decreased with increasing ATH content. In the first cycle of the salt-fog test, the leakage current increased with increasing ATH content. The relatively higher hydrophobicity of the specimen with a low ATH content than the specimen with a high ATH content had an inhibitory effect on the initial leakage current development. In the last cycle of the salt-fog test, the heat from dry band arc discharge became the dominant factor affecting the surface aging after the loss of hydrophobicity, and the specimen with a higher ATH content inversely had a better inhibitory effect on leakage current development. According to the X-ray photoelectron spectroscopy (XPS) analysis results, when the energized SR was exposed to a moist environment, the heat from dry band arc discharge and the hydrolysis reaction caused a change in the binding state between Si and O, which is considered the mechanism responsible for material degradation. During this process, the higher content of ATH had a remarkable effect on alleviating surface aging.