New techniques for estimating the condition of high voltage polymeric insulators

Abstract

Insulators manufactured from polymeric materials are widely used by many electricity companies although there is concern about how degradation of the polymeric material of insulators might affect their lifetime. The question arises as to how utilities might best manage large populations of degrading composite insulators that are often dispersed over great geographical areas. In this paper the complete life cycle costs of polymeric insulators in large electricity networks are examined and it is concluded that failures of inexpensive components can generate significant real costs to the network owners and great indirect costs to the community. The policy of replace on failure is discussed and it is suggested that the application of condition based maintenance is needed to reduce costs. Failure modes of insulators are reviewed and a new technique for determining numerical indicators of insulator condition, developed by the author and co-researchers, is described that is based on analysis of samples of polymeric insulation taken 'live' from the high voltage network. The condition indicators developed for EPDM and silicone rubber insulation are described and results from sampling in 11 kV and 132 kV networks are presented.