Composite insulators are today quite widely used and well-accepted throughout the world. In China, for example, there several million such insulators already in service on HV transmission lines up to 1000 kV AC and ± 800 kV DC. In addition, huge numbers of silicone-housed zinc oxide surge arresters as well as silicone-housed bushings have already been applied in this country for years.
SR composite insulators are now employed throughout China as the major countermeasure to pollution. Most operate in areas of medium to heavy pollution and where porcelain or glass insulators had experienced severe pollution flashovers on an annual basis. Since no special cleaning is required for these insulators, maintenance work is significantly reduced compared with porcelain/glass insulators. Indeed, the overall experience so far is that after replacing porcelain/glass with SR insulators, outages trigerred by pollution flashover have basically been eliminated. It was for these reasons that for 1000 kV UHV AC and ± 800 kV UHV DC projects, where these lines pass through polluted areas, large numbers of SR insulators having comparatively short creepage distances have been applied.