Research On Interlayer Interface Effect Of Epoxy Resin In Power Equipment

With the increase of voltage level,large high-class power equipment represented by extra high voltage and casted appliances represented by electronic packages are facing the requirement of miniaturization based on satisfying reliability.Epoxy resin insulators,dry bushings and electrical devices poured by epoxy resin often introduce epoxy-epoxy interface structure during the manufacturing process,and the location is often the starting point for insulation and mechanical damage to occur.Therefore,the study of the mechanism of interlayer interface effect on material properties is urgently needed.At present,less attention has been paid to the interfacial structure formed by the epoxy curing cross-linking reaction,and the microscopic formation mechanism of the interlayer interface of epoxy resin has not been clarified.Therefore,in this work,the effect of interfacial effect on the mechanical strength,cracking resistance,and dielectric properties of the material is investigated by preparing epoxy-epoxy interfacial structures.Firstly,the changes in the introduction of interlayer interfaces on the development of interfacial cracks and the degree of cross-linking at the interfaces were analyzed by preparing laminated epoxy specimens and roughness treatment of the interfaces.The experimental results show that the introduction of the interlayer interface hinders the crack development to a certain extent,and the cross-linking reaction at the interface affects the size of the liquid rubber particles precipitated from the epoxy resin on the doped filler side.Secondly,the cracking resistance of the interlayer interface specimens of epoxy resin was analyzed by a combination of experiments and simulations,and the strain variation at the interface of different types of specimens was studied.The results show that the simulation results of the coupled multi-physical field model of the interlayer interface and the experimental results are basically consistent.The use of higher curing agent content in the post-cast layer had a greater effect on the strain at the interface during the cooling and shrinkage phase of the curing process.Under the action of thermal strain and interfacial force,“fan-shaped” cracks develop at the interface.Finally,the mechanical strength,dielectric spectrum characteristics of different specimens were measured,and the AC breakdown characteristics and electrical dendrite growth characteristics in different electric field directions were analyzed.The study shows that after the introduction of the interlayer interface,decreasing or increasing the curing agent content of the post-cast layer will sacrifice certain mechanical strength but increase the dielectric constant of the material.Interface perpendicular and parallel electric field direction arrangement,the material breakdown field strength of the smallest corresponding number of sandpaper mesh is different,and the breakdown mechanism is also different.In addition,the interlayer interface has the effect of "attracting" the growth of electric branches,the introduction of the interface will slow down the growth rate of electric branches.This paper reveals the interlayer interface effect of epoxy resin in electric power equipment through experimental measurements combined with simulation techniques.The mechanism of this effect on the mechanical strength,cracking resistance,and dielectric properties of the epoxy castings can be used to analyze the interface modification.Thus,the performance parameters of the actual castings can be optimized to provide a theoretical basis for miniaturization and high reliability of electric power equipment.