Characterization of field-aged 400 kV silicone rubber composite insulators

A number of silicone rubber composite insulators have been removed after 15 years of service on a coastal 400 kV transmission line in the UK. Extensive analysis of their surface degradation is provided along with a description of their appearance. Material analysis shows cracking and oxidation of the surface. Ageing effects were far from uniform over each shed, the greatest oxidation being on the top surfaces of the sheds on the south side. Microscopy, EDX and FTIR were found to be the most useful and effective tools for analysis of these polymeric insulators.