Study on Surface Charge and Mechanical Properties of Epoxy Impregnated Paper Composites

Epoxy impregnated paper is the main insulation material of bushing capacitor core, which withstand electrical and mechanical stress for a long time. In this paper, the surface potential characteristics of epoxy impregnated paper and pure epoxy resin in the application environment of strong normal electric field components were compared, and the flashover and mechanical properties were tested. The results show that the conductivity of corrugated paper is higher than pure epoxy resin, and some defects are introduced into the composite material, which makes it easier for carriers to migrate. Thus the composite material has higher conductivity and local non-uniformity. Result in the accumulation of surface charge is large and the distribution is uneven. It leads to the distortion of electric field and the decrease of flashover voltage, which is the inducing factor of the actual flashover accident of bushing. In terms of mechanical properties, the corrugated paper can relieve part of the stress, and the tensile strength and elongation at break of the epoxy impregnated paper composite insulation material are increased by 41.74% and 48.31% respectively, compared with the epoxy resin. Because the surface of epoxy impregnated paper composite insulation material is mainly composed of epoxy resin, there is little difference in hardness between them. The conclusions of this paper can provide a reference for the operation of bushing capacitors core under mechanical and electrical stress.