Surface Ageing of HV Composite Insulators on 400 kV Lines

The market for polymeric insulators has now existed for over 20 years enabling a comparison to be made between good-quality service-aged products and the original expectations of performance. This paper presents investigations of field-aged composite silicone rubber insulators, which have been deployed for 15 years on a 400 kV transmission line in a coastal region of the UK. Measurements of contact angle, and surface chemistry through energy dispersive X-ray analysis (EDX) and Fourier transform infrared spectroscopy (FTIR) are given. Evidence is presented of substantial variations of key surface properties along the length and circumferentially around the insulator. Ageing mechanisms and processes are discussed in this context.