Accelerated-ageing test for RTV-coated insulators: analysis of electrical and material properties

An accelerated-ageing test is conducted on three room-temperature-vulcanised (RTV) coated porcelain insulators, until the initiation of ageing phenomena, in a salt-fog-ageing test chamber. The test conducted was similar to the IEC 1109 1000 h test, but with scaled-down test set-up parameters to address criticisms published in the literature. The results obtained prove the effectiveness of the hydrophobicity of the surface in terms of electrical and material properties. The electrical properties were obtained by online monitoring of the leakage current. The material characteristics were evaluated by conducting energy-dispersion X-ray (EDX) analysis and X-ray-diffraction (XRD) analysis. In addition, the fog dynamics in the test chamber on the direct fog (DF) sample, which is in the axis of nozzle columns, and indirect fog samples IF₁ and IF₂, which were slightly away from the nozzle column axis, was evaluated. It was concluded that the RTV-coated samples which were kept away from the nozzle-column axis, i.e. IF₁ and IF₂ samples, showed symptoms of initiation of ageing earlier than the sample which was in direct fog mode.