Partial discharge measurement as a diagnostic tool of the early ageing of silicone rubber insulation

The paper presents an investigation on the use of partial discharge (PD) measurements as an alternative method to study the development of leakage current (LC) on silicone rubber insulators under salt-fog conditions. Visual observations of surface discharges on the insulators are performed with an image intensifier while simultaneous measurements of low level LC and PD are made. Signal processing techniques are then applied to the recorded data to study the trends. The results show that the information provided by the PD signals are useful to understand the performance of the insulators particularly when the LC fails to distinguish their design performance. PD is, therefore, a sensitive method to investigate the loss of hydrophobicity and the early ageing stage of silicone rubber insulators.