Study On Corona Aging Characteristics Of Epoxy Resin In Humid And Hot Environment

Epoxy resin has a high degree of adhesion,good electrical insulation,and good processability,and has a small shrinkage rate during molding.Therefore,epoxy resin has been used in generators,electronic devices and various k V transformers.The casting of important insulating components.However,in the long-term working process,the insulation aging phenomenon generally exists in the insulating material,which affects the reliable operation of the power system.The damp and heat factors generated in the environment will affect the insulation aging ability of epoxy resin materials,and then accelerate the aging rate of epoxy resin,thus seriously affecting the safe operation of insulating components on the device.The halo aging properties are of great significance.In a humid and hot environment,after corona aging test of epoxy resin material,this paper analyzes the moisture absorption characteristics,infrared spectral characteristics,surface topography image,flashover voltage,leakage current,dielectric loss,volume and surface resistivity of the samples after the test.Tests were carried out,and the changing laws of physical and chemical properties and electrical properties were analyzed.The main research contents of this paper are as follows:（1）The test results of the hygroscopic properties of epoxy resin after corona aging show that:the control variable method is used in this paper to set the ambient humidity to 95%RH and the duration of 100h of humidity for epoxy resin corona aging at different temperatures.Thermal corona aging,when the ambient temperature is less than 60°C,the quality of the epoxy resin increases with the rise of the temperature.When the ambient temperature of the epoxy resin is greater than 60°C,the epoxy resin occurs due to corona aging at a higher temperature.The desorbed mass is greater than the moisture absorption,resulting in a decrease in the quality of the epoxy resin as the temperature increases.Under different humidity,set the ambient temperature to 80℃,and carry out the damp heat corona aging for 100 hours.As the humidity increases,the moisture absorption of epoxy resin gradually decreases.When the humidity is 95%RH,white substances are precipitated on the surface.（2）The infrared spectrum and SEM test results of epoxy resin after corona aging show that:the epoxy resin sample after damp heat corona aging has a characteristic absorption peak corresponding to alcohols in the band of 1000-1050cm^-1,while in the band of 1000-1050cm^-1 At the band of 750-810cm^-1,there is a meta-disubstituted benzene ring.The effects of damp-heat corona aging of epoxy resins on the internal groups of epoxy resins at different temperatures and humidity are different,but not obvious.When the temperature is less than60℃or the humidity is less than 65%RH,the damp heat corona aging has little effect on the internal group.The combined structure is decomposed to generate more free radicals,and the increase of-OH groups also promotes the process of chemical hygroscopicity.In a humid and hot environment,the bombardment of high-energy electron beams caused the destruction of the epoxy resin surface structure,and the surface of the sample became fluffy under the influence of moisture absorption,which promoted the peeling of the epoxy resin surface layer.The SEM results show that in the high temperature and high humidity environment,holes,cracks and ravines appear on the surface of the epoxy resin,and with the increase of temperature and humidity,the central area of the electrode appears layer-by-layer peeling off.（3）The electrical characteristics test results of epoxy resin after corona aging show that:with the increase of ambient temperature or ambient relative humidity,the internal deterioration of epoxy resin aging samples is serious,the polar groups are easily turned,and the relaxation polarization loss increases,resulting in dielectric Loss increases.The volume and surface resistivity of epoxy resin decreased with the increase of aging temperature and relative humidity,but the electron beam bombardment directly acted on the surface of epoxy resin,which destroyed the structure of epoxy resin and promoted the moisture absorption of the surface layer,resulting in surface resistivity.The greater the drop,the more severe the loss of insulating properties on the epoxy surface.Due to the serious damage to the surface insulation properties of the aged epoxy resin samples,the formation of an effective conductive channel with water molecules in the air in a high humidity environment leads to a rapid drop in the dry flash voltage and wet flash voltage,and a significant increase in the leakage current.The samples with higher aging temperature or humidity have smaller wet flash voltage value,larger leakage current and stronger waveform periodicity.Through comparison,it is found that temperature has greater influence on flashover voltage and leakage current.