Research Findings Comparing Performance of Different Insulator Designs on Distribution Lines in Tropical Environments

摘要

The nonceramic and RTV coated porcelain insulators have performed well, since their installation in 1995 under marine and industrial pollution conditions in tropical environments in Sri Lanka and Tanzania. No flashovers have been reported on them, despite the heavy service conditions. Simultaneously, flashover events have taken place on porcelain cap&pin insulators, acting as references, at locations with a high concentration of salt pollution. Surface damage, caused by intensive dry-band discharges, has also been found on the tested porcelain insulator. Among the nonceramic and RTV coated insulators, only the EPDM insulators have completely lost their surface hydrophobic properties. The surfaces of these insulators have degraded (discoloration), and have shown signs of some erosion. The silicone rubber housings and coatings have, in general, preserved the water-repellent property, but even here, some trends have been noticed. The hydrophobicity of the insulators installed under industrial pollution conditions has basically remained unchanged. It should be also noted, that in the location with cement pollution, the contamination layer could be removed from the silicone rubber surfaces. This indicates that the silicone surfaces can even be more prone to rain or artificial washing. Algae contaminants can grow on silicone rubber in the tropics, mainly on partially shaded surfaces. Algae contamination reduces the hydrophobicity of polymeric surfaces, although their conductivity remains low. Algae contamination also leads to reduce the insulator wet flashover voltage. However, since they mainly grow in clean environments, the risk for an insulator flashover under field conditions is perhaps not too large.