The operation and maintenance experience of composite insulator shows that the interfacial heating is a relatively severe form of defect. For studying the influence of interfacial heating of composite insulator on the water permeability of sheath

a thermal circuit model of the composite insulator is constructed firstly

the effectiveness of the model is verified and the influence of sheath thickness on internal and external temperature rise is deduced. The results show that in case of constant interfacial heating capacity of faulty composite insulator

the temperature at the defect of interfacial of composite insulator with thicker sheath is higher

and the sheath surface temperature is lower. The influence of interfacial heating of composite insulator on the water permeability of silicone rubber is studied by using fuchsin solution to penetrate the silicone rubber sheet. The results show that the penetration depth of the solution is approximately linear with the square root of time. The higher the temperature is

the faster the water permeability of silicone rubber is. Moreever

the effects of water and temperature on the hydrolysis of core rod materials are analyzed. The results show that the increase of interfacial temperature has not only promoted the penetration of water vapor

but also the hydrolysis of resin and glass fiber filament with the increase of water vapor content and temperature. The research work can provide guidance for on-site operation and maintenance of heating composite insulators.