WETTABILITY AND THERMALLY STIMULATED DEPOLARIZATION CURRENT SPECTRA OF NATURALLY AGED SILICONE-RUBBER INSULATORS

Investigations are reported on high- and low-temperature vulcanized si licone rubber composite insulators that were exposed to service for th ree, nine and eleven years under industrial or marine pollution condit ions. Wetting angles and thermally stimulated depolarization (TSD) cur rent spectra were measured. Microscopic observations of selected insul ator surfaces were carried out as well. The prolonged services cause g radual and inhomogeneous losses of hydrophobicity on surfaces and insi de of insulator housing materials. It is shown that there exists a cor relation between the measured TSD current spectra and the wettability changes. In addition, the spectra also allow to predict art ability to support a process of hydrophobicity recovery at a housing surface. It seems that TSD measurements may be applied as a complementary test me thod during performance assessment of silicone rubber composite insula tors.