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Among the new insulating materials widely used in high voltage outdoor insulation
systems, silicon rubber materials also called polymeric materials are very important; during last
20 years they have been applied for manufacturing outdoor insulators. These materials are organic
in nature; therefore they are prone to decomposition under different environmental conditions; the
most important among these conditions for consideration of w.r.t. of high voltage electrical
insulation is the hydrophobicity. Hydrophobicity is treated as the resistance to formation of conducting water tracks that increase leakage current, chances of flashover, and other deterioration effects. The superior contaminant performances of polymer outdoor insulating materials are regarded as the contribution of their hydrophobic surfaces. In other words, it is the formation of water beads on surface, which resist the flow of water in continuous conducing track. Hydrophobicity theory, its importance for polymeric silicon rubber insulators, methods of hydrophobicity measurements - especially by leakage current, low molecular weight component chains responsible for hydrophobicity recovery, chemistry of hydrophobicity loss and recovery, hydrophobicity recovery related with temperature, humidity, UV radiation, corona, electric field and dry band arcing are overviewed in this paper. |
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