Research On Dielectric Properties Of Epoxy Resin/Silicon Carbide Composites

With the continuous growth of China's economy and the increasing demand for electric power,large capacity and long-distance DC transmission has been widely used and developed,which also puts forward new requirements for high-voltage and ultra-high voltage DC transmission technology.Compared with AC transmission system,DC transmission has higher requirements for insulation medium.Polymer based non-linear insulation medium has the characteristics of improving electric field distribution,and voltage insulation field has been widely used.Therefore,it is of great significance to study the material properties,dielectric properties and influencing factors of polymer based non-linear composite for the application of non-linear materials.In this paper,epoxy resin(EP)was used as the matrix and nano silicon carbide(Si C)as the inorganic filler to prepare EP / Si C composite materials with different filling content.The polarization and conductivity characteristics of the composite materials were studied.The research results show that the pre-treatment temperature can affect the crosslinking density of the molecular chain in the interaction zone between Nano Si C particles and epoxy resin matrix,and the pre-treatment temperature of the composite materials in this study is determined to be 120 ?.The relationship between the polarization and depolarization current and time of the composite materials conforms to the general law of relaxation polarization(Curie formula).The relaxation polarization current and the steady-state DC conduction current in the polarization and depolarization process can be obtained by using Curie formula filtering analysis.Compared with 30 min DC conduction current test,it is found that the filling content of inorganic filler affects the accuracy of fitting results.With the increase of the inorganic filler content and the applied electric field strength,the polarization process of the composite materials is nonlinear,and the depolarization process is linear.The relationship between relaxation polarization intensity and time was fitted by saturation function.It was found that the polarization process did not reach steady state in 7200 s.The research results show that the conductivity of the composite materials increases with temperature build-up,and the electric field strength of the nonlinear inflection point decreases gradually,which indicates that the conductivity mechanism of the composite materials has a thermal shock jump process.When the filling content of Si C reaches a certain value,with the increase of the filling content,the influence of temperature on the conductivity of the composite materials under high field is gradually weakened.Through the simulation analysis of gas insulated transmission line(GIL)using EP / Si C composite materials basin insulator,it is found that the application of non-linear conductivity composite material has no obvious influence on the temperature distribution of GIL,but it can effectively homogenize the electric field distribution of GIL and reduce and homogenize the surface electric field strength of the basin insulator.