End-of-life and replacement strategies for RTV silicone rubber coatings

The paper provides several methods to assess the condition of RTV coated porcelain/toughened glass insulators in the field. Visual observations of arcing and audible corona are the first indications that signal changes to the coating have taken place. It emphasizes that in the absence of reliable data one can use observations based on hydrophobicity to evaluate when maintenance or replacement of the coated insulators is necessary. Life extension strategies are suggested. It also demonstrates that there are differences in the hydrophobicity characteristics among commercially available coatings, and these can be quantified using standard laboratory techniques. Field experience suggests that the life of the RTV coatings can exceed 10 years even under the severest conditions of pollution.