The performance of silicone rubber for HV insulators under natural tropical aging

Silicone rubber is a new insulation material for HV outdoor insulators. In order to know the long term of its performance we investigated the aging of the material under natural tropical environment. This paper reports the result of a study on dielectric hydrophobicity and loss of weight. The samples of RTV and HTV silicone rubber with different filler levels were installed in open air plane in Bandung, Indonesia. Some parameters as the changes of weight, dielectric properties (/spl epsiv//sub r/ and tan/spl delta/), and hydrophobicity (contact angle) were periodically measured each week during 231 weeks (4.8 years). The experimental results showed that RTV and HTV silicone rubber showed still better hydrophobicity. However, greater changes of weight, /spl epsiv//sub r/ and tan/spl delta/ were observed. Water absorption played unimportant role in the change of /spl epsiv//sub r/ and tan/spl delta/. Removal of water trapped in samples clarified this speculation. HTV and RTV samples with higher filler content showed higher ability to resist the surface degradation and weight losses. Analysis of the residual weight may be used to expect the lifetime of material in service under natural tropical climate.