Ageing of transmission line insulators: The past, present and future

Contamination flashover as a result of pollution severity leading to costly outages plagues insulator performance. Apart from the problem of flashover, failure of insulators as a result of ageing has also lead to service disruption. Leakage current (LC) is a good measure of insulator surface condition and thus its magnitude has been used as a parameter for monitoring insulator flashover and pollution severity, but this parameter is not effective in monitoring ageing insulator. Furthermore, field monitoring and diagnosis of ageing insulators has not been exploited. This paper presents an overview of the ageing mechanism of both ceramic and polymeric insulators. Previous studies on the correlations of LC with pollution severity, environmental parameters and insulator performance are discussed. A review of recent studies on relationship between LC with ageing insulators and the possible future areas of research on monitoring and diagnosis of ageing insulators are presented.