Physicochemical And Flashover Properties Of Silicone Rubber Under High Voltage In High Humidity Environment

Composite insulators have been widely applied in high voltage transmission lines due to their outstanding anti-pollution flashover performance.With the rapid development of the national economy and the continuous advance of the UHV project and strong smart grid engineering,a large number of composite insulators are applied to the key projects of AC and DC voltage levels above 500 kV.At present,researches on physicochemical properties and flashover characteristics of silicone rubber in high humidity environment are rarely reported.Based on the existing researchs at home and abroad,the physicochemical properties and the flashover characteristics of composite insulators silicone rubber in high humidity environment were tested.The main work of this paper is as follows:In the artificial climate laboratory,different charged voltages were selected according to the leakage distance and the relevant standards.The physicochemical properties of silicone rubber were tested,and the difference of flashover voltage between samples was compared.The effects of withstand time,charged voltage and water conductivity on physicochemical properties and flashover characteristics of silicone rubber were analyzed.The following conclusions are obtained:(1)In high humidity environment,the water droplets on the surface of silicone rubber changes the distribution of electric field along the surface.The increases of local electric field produce corona discharge.The force of electric field and the decrease of hydrophobicity make the adjacent water droplets converge and produce arc discharge.(2)In high humidity environment,the corona discharge and arc discharge on the surface of silicone rubber change the physicochemical properties.The static contact angle decreases,and the hydrophobicity decreases or even loses.The molecular chain cleavage,the degree of crosslinking of main chain and the content of hydrophobic group in side chain decreased.The decomposition of inorganic flame retardant ATH at high temperature leads to the decrease of arc erosion resistance.The surface is uneven,and there are physical defects such as holes and cracks.The increase of moisture content and interface defect leads to the increase of complex permittivity and dielectric loss.(3)With the increase of withstand time,charged voltage or water conductivity,the surface discharge of the silicone rubber material is more intense and the hydrophobicity is reduced.Therefore,the chemical degradation and physical defects are more serious.(4)Under the continuous action of high voltage and high humidity,the surface properties of the silicone rubber materials are degraded.The formation of water band,large continuous water film and the decomposition of inorganic flame retardants are the main reasons for the decrease of the flashover voltage along the surface.(5)The increase of withstand time,charged voltage or water conductivity,the leakage current of the silicone rubber material increases,and the area of water band and water film increases.Therefore,the surface flashover voltage decreases.(6)In the high humidity environment,the surface flashover voltage of the silicon rubber and the water conductivity still meet the negative power function.The influence coefficient of the water conductivity on the flashover voltage increases with the increase of the withstand time,which is related to the formation of large film and the decrease of the arc erosion resistance.