Effect of dry band arcing on the surface of RTV silicone rubber coatings

To elucidate the chemical changes due to dry band arcing, under wet and contaminated conditions, of room temperature vulcanized (RTV) silicone rubber used for coating HV outdoor insulators, the thermal impact of the arcing on the rubber surface was investigated. A loss of hydrophobicity, resulting in a reduction of the withstand voltage and subsequent failure of the insulators, was observed. The surface of the coatings was subjected to a salt-fog with electrical stress. Electron spectroscopy for chemical analysis (ESCA) was used to investigate the chemical changes of the surface. The results of attenuated total reflection Fourier transform infrared spectroscopy and ESCA indicate the formation of low-molecular-weight polydimethylsiloxane (PDMS), the reduction of CH₃ groups, and crosslinking of PDMS backbone chains at the surface due to dry band arcing