Abstract
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.
Highlights
Since the beginning of the power system more than 160 years ago, porcelain and glass have dominated as the selections for outdoor insulator materials because these ceramic insulating materials can generally withstand outdoor stresses
In this study, the influence of the moist environment on the aging performance of silicone rubber (SR) used for outdoor insulation was investigated by a cycling salt-fog test
High-temperature vulcanized (HTV) SRs with different alumina trihydrate (ATH) filler contents were adopted as the test specimens
Summary
Since the beginning of the power system more than 160 years ago, porcelain and glass have dominated as the selections for outdoor insulator materials because these ceramic insulating materials can generally withstand outdoor stresses. In addition to the problems of easy breakdown during transportation, friability, and heavy weight, the pollutionflashover performance of these insulators is poor due to the hydrophilic surface, especially in moist environments with high humidity. Silicone rubber (SR) materials with low free surface energy are widely applied because their surface hydrophobicity contributes to superior performance in resisting wetting. Water droplets; the conductive contaminants dissolved in the water are discontinuous. Another important feature of SR compounds, compared to other polymers, is their ability to recovery from the loss of hydrophobicity. Migration of preexisting low molecular weight (LMW) polydimethylsiloxane (PDMS) fluid from the bulk to the damaged surface are considered as possible mechanisms responsible for the hydrophobic transfer and recovery [4]–[6]
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