Surface Ageing ofHV Composite Insulators on400kVLines

Themarket forpolymeric insulators hasnow existed forover20years enabling acomparison tobe madebetween good-quality service-aged products and theoriginal expectations ofperformance. Thispaper presents investigations offield-aged composite silicone rubber insulators, whichhavebeendeployed for15 years ona400kVtransmission line inacoastal region oftheUK.Measurements ofcontact angle, andsurface chemistry through energydispersive X-rayanalysis (EDX)andFourier transform infrared spectroscopy (FTIR) aregiven. Evidence ispresented ofsubstantial variations ofkeysurface properties along thelength and circumferentiall y aroundthe insulator. Ageing mechanisms andprocesses arediscussed inthis context.