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Surface analysis of 400 kV silicone rubber composite insulators is presented. These insulators have experienced 15 years of service on a coastal 400 kV transmission line. Inspection of the insulators shows low levels of degradation through cracking and oxidation of the surface. This has been quantified by microscopy, energy dispersive Xray analysis (EDX), Fourier transform infrared spectroscopy (FTIR) and Raman spectroscopy. The analysis shows non-uniform ageing over each shed and ageing on the south side more advanced than on the north side. It is believed that non-uniform ageing was due to environmental factors including natural UV radiation and prevailing wind direction, and the resultant pattern of growth of organic species. EDX and FTIR were found to be the most useful and effective tools for analysis of these polymeric insulators.

A number of silicone rubber composite insulators have been examined following 15 years of service on a coastal 400 kV transmission line in the UK. Extensive measurements of their hydrophobicity, as determined by contact angle, are given along with a description of their appearance. The hydrophobicity change varied from the low voltage end to the high voltage end with the lowest contact angles being found in the middle of the string. The sheds also aged differently around their circumference and this was reflected in discoloration differences on different sides of the insulator, in addition to hydrophobicity changes. The greatest change to properties was witnessed on the core of the insulators on which contact angles of less than 70 degrees were recorded.

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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.