Research On Dielectric Properties Of EP Nonlinear Composites

In recent years,with the rapiddevelopment of the extra(ultra) high voltage alternating current(AC)/direct current(DC) transmission technologies, the problem of the electric field homogenization and regulation of high voltage electrical equipment become increasinglyserious. For example,the distortion of the local electric field in the ?800 k V HVDC wall bushingswill lead to the higher failure rate,and the flashover along the surface of the high voltage Gas Insulated Station(GIS)occurs because of the surface charge accumulation. Since nonlinear insulating material whose electrical conductivity and/or dielectric constant are controlled by the electric field has the ability of homogenizingthe electric field distribution and inhibiting the electric charge accumulation. The application of nonlinear insulating material for the insulation of high voltage electrical equipment is expected to improve the reliability and compactedness of the products, reduce the manufacturing difficulty and cost and guarantee the stability of power grid operation.In this paper, nano composite materials were prepared by adding nano silicon carbide(Si C), nano graphite and other inorganic fillersto epoxy resin(EP). The influences of the types of nano inorganic filler, addition amount andcomplex formulationon theelectrical properties such as AC and DC breakdown strengths, DC conductivity characteristics, space charge distributions, ACdielectricconstant and loss factor, etc were investigated in the experiment.The research results show that adding a right amount of nano Si C and nano graphite can all improve the conductivityproperties of the EP matrix nanocomposite materials, and the conductivity nonlinear coefficient of Si C/EP nanocomposite material is better than that of graphite/EP nanocomposites. The electrical conductivity of EP matrix nanocomposite is greatly influenced by the temperature. The DC breakdown strengthsof EP nanocomposite addedwith nano Si C and nano graphite obviously decrease and the effect of nano Si C is larger. The space charge accumulation of EPmatrix nanocomposite is effectively restrained byaddingasmall amount of nano graphite. Along with the increasingof the content of the nano fillers, the dielectric constant and dielectric loss of EP matrix nanocomposite all gradually increase.