Influence Of Micro And Nano Composite Coating On Surface Charge Dynamic Characteristics Of Epoxy Resin

Epoxy matrix composites have wide applications in the electrical equipment because of their excellent electrical insulation properties.However,the surface of epoxy resin is easy to accumulate charge under prolonged DC electric field,which will affect the insulation performance seriously including electric field distortion and sharp decrease of surface insulation resistance.The charge accumulation on the surface of the material is closely related to the surface state of the material and the surface coating can control the surface condition of insulating materials on demand,thus possessing broad application foreground.Therefore,the study of influence of micro and nano composite coating on surface charge dynamic characteristics of epoxy resin has great significance for improving the performance of epoxy resin in dc conditions.In this paper,the micro and nano composite coating preparation platform,surface charge dynamic characteristics test platform,the isothermal surface potential decay test platform and flashover characteristics test platform were built.Based on these platforms,micron SiO2/EP coating,nano SiO2/EP coating and nano TiO2/EP coating were prepared as the coating materials which were sprayed on the surface of the epoxy matrix as samples.Then the surface charge dynamic characteristics of the sample were studied by the electrostatic probe method and the flashover characteristics were also tested.Through analyzing physical and chemical characteristic and trap characteristics of coating,the control mechanism of coating play in the surface charge was discussed.The results show that,after the micron and nano composite coating coated on the surface of epoxy resin,the surface charge accumulation was suppressed and the preset voltage flashover voltage was improved meanwhile.When the content of particles in the coating was 3 wt%,the preset voltage flashover voltage was the highest in the same particle doped sample.But when the content of micron SiO2 and nano SiO2 particles in the coating was 5 wt%,the surface of the material accumulates a large amount of charge,while the preset voltage flashover voltage dropped.The surface charges were mainly accumulated near the electrode,the main source was the electrode injection under the normal electric field.The surface charges near the anode were mainly caused by the residence effect caused by the charge trapping,and the surface charges near the cathode were mainly caused by the adsorption due to the normal electric field.Adding a small amount of particles to epoxy resin could effectively improve the shallow trap density and conductivity of material surface,so this coating can effectively suppress the surface charge accumulation of epoxy resin and improve preset voltage flashover voltage.But the content of particles should not be too much,because excessive particle content would lead to local agglomeration of particles and make surface charge easier to accumulate.Based on the analysis of the characteristics of the coatings,this paper preliminarily selects the coating materials which showed the most significant effect on suppressing charge accumulation.