Performance Improvement of the Ceramic Outdoor Insulators Located at Highly Polluted Environment Using Room Temperature Vulcanized Silicone Rubber Coating

Ceramic insulators are widely used in transmission as well as in distribution lines. As outdoor insulators, the ceramic insulators are subjected to environmental stresses. In particular case, the insulators may severe high pollution exposure. Under the polluted condition, high leakage current will flow on the insulator surface and dry band arching may take place. The phenomena may initiate the insulator flash over leading to the failure of the lines. Several efforts may be taken to improve the insulator performance under polluted condition. Recently, adding of hidrophobic agent on the insulators was introduced to improve the performance of ceramic insulators under polluted condition. This paper reports the experimental results on the application of room temperature vulcanized (RTV) silicone rubber coating on the medium voltage ceramic insulators under various environmental conditions. The samples were put in a test chamber with controlled humidity and pollution condition. The characteristics of RTV Silicon Rubber coated insulator were analyzed, such as its leakage current (LC), hydrophobicity (indicated by measuring contact angle) and Surface Smoothness (indicated by Scanned Electron Microscopy (SEM)) of the RTV Silicon Rubber insulator surface. The LC’s waveform parameters such as magnitude and harmonic content (as indicated by the total harmonics distortion (THD)) were analyzed. It was found that the coating was significantly suppressed the magnitude of leakage current and drastically eliminated the harmonic content. The gradient of cross product value between LC magnitude and THD was proved to be a better indicator to show insulator condition rather than LC or THD alone. The coating also significantly increased the flash over voltage of the insulator. Surface analysis indicated that increasing of the water repellence and enhancement of surface resistance of the insulators played important role in the increase of the insulator performances. These experimental results will be the basis of application of RTV Silicon Rubber coated insulator under polluted conditions, especially in Indonesia.