Quantitative evaluation of the surface weathering of non-ceramic insulators

Some composite materials have performed significantly better than others in HV overhead line outdoor insulation applications, with a large proportion of the failures which have occurred in service generally related to a few specific products. Advances in materials technology over the next ten years can be expected to widen further the range of products available, and therefore test standards for the determination of the long-term performance of nonceramic insulators must include more meaningful pass/fail criteria for evaluation of ageing, so that selection for long-term reliability can be made more objective. The range of diagnostics techniques described by the author provides a good picture of the changes in surface characteristics which are responsible for increased probability of flashover in service conditions