Study On Trap Characteristics Of Oil-immersed Composite Insulation Jacket Under Corona Aging

In recent years,composite insulation materials have been gradually used in power systems due to their excellent water repellency,high temperature resistance,stain resistance and high hardness.Compared with ceramic materials,composite insulation materials have inherent advantages in preventing the explosion of substation equipment.Therefore,research on composite insulation jackets is of great significance.This paper is based on the research and application of the key technology of long-life and high-reliability substation equipment with composite insulation jacket.The oil-immersed composite insulation jacket material widely used in power system--HTV silicone rubber is the research object.The following research work was carried out on the effects of pipe oil leakage and electrical aging on the external insulation properties of silicone rubber:The corona aging test platform of high temperature vulcanized silicone rubber was set up.The 25 kV corona voltage and 10 mm discharge gap were selected by simulation.The AC corona aging experiment was carried out on silicone rubber at different times.The FTIR and SEM techniques were used to study the microscopicity of silicone rubber under different AC degrees under AC corona.Molecular groups and surface morphology changes.Studies have shown that as corona aging intensifies,flocculent inorganic oxides appear on the surface,which are no longer flat and become rough and gradually develop into large pores.The long molecular chain of silicone rubber is destroyed,the increase of small molecular chains and free radicals on the surface,and the formation of various strong polar groups,so that the surface structure of silicone rubber cross-links with each other,and the flexibility is reduced to form various kinds.defect.A surface potential attenuation test platform was built to perform positive and negative corona charging on silicone rubber after immersion in oil and immersion oil.The surface potential attenuation curve was measured to calculate the energy level and density of the shallow trap,and the corona aging and The effect of insulating oil on the trap characteristics of silicone rubber.The results show that with the increase of aging degree,the electron depth trap and the depth of the hole depth trap are reduced,the peak depth of the deep hole trap and the electronic deep trap are reduced,and the peak density of the shallow trap increases,while the peak of the electron shallow trap The density increases first and then decreases.The energy level and density change of the immersed aging silicone rubber are consistent with those of the unimmersed aging silicone rubber.However,the flocculent inorganic oxides generated by aging of silicone rubber are soaked in the insulating oil to form oil stains,which makes the surface flashover of silicone rubber more likely after agingA flashover test platform was built to measure the AC flashover voltage of silicone rubber after immersion and immersion in oil,and the influence of insulating oil and aging degree on the flashover characteristics of silicone rubber was analyzed.Studies have shown that corona aging causes the inorganic rubber oxides in the surface layer of silicone rubber to cause the surface of the silicone rubber to accumulate charge,which reduces the flashover voltage between the electrodes.When the oil-impregnated silicone rubber is corona-aged,the insulating oil coating promotes the contact between the electrode and the silicone rubber to reduce the dispersibility of the flashover voltage,and the flocculent inorganic oxide formed by the aging of the silicone rubber is infiltrated into the insulating oil to form oil stain.The silicone rubber after the aging of the oil is more likely to flash on the surface.The relationship between surface charge and flashover voltage was established,and the influence mechanism of corona aging on the surface flashover of silicone rubber was analyzed.Studies have shown that as the corona aging time increases,the deep surface trap gradually develops into a shallow trap,the deep trap level decreases,the density decreases,and the deep trap plays a major role in the electron binding of the silicone rubber surface,so the trapping charge is weakened.Promote more charge trapping and migration.At the same time,aging increases the carrier mobility,increases the conductivity,promotes the development of secondary electron collapse,increases the collision energy between electrons and gas molecules,and contributes to the formation of the desorption gas layer of the silicone rubber,resulting in a decrease in the surface flashover voltage of the silicone rubber.