Improved Electric Field Distribution of the Valve Side Bushing Impregnated with Epoxy/GO Nanocomposite

Field grading within the dry-type bushing insulation presents a major challenge for DC applications due to the highly temperature-dependent conductivity of the epoxy resin insulation. An electric field regulation method based on the epoxy/graphene oxide (EP/GO) nanocomposites with reduced temperature coefficient of conductivity is proposed. The DC conductivity of EP/GO nanocomposites with different loadings of 0, 0.05, 0.1 and 0.5 wt% at various electric field strength and temperature are investigated. Obtained results show that the temperature coefficient of conductivity of EP/GO nanocomposites is reduced with the increasing GO content. The improvement of electric field distribution within the bushing insulation is verified when the EP/GO nanocomposites with appropriate content are employed, based on an established ±800 kV valve-side bushing for a converter transformer. However, more defects will be introduced by the GO fillers with excessive content (0.5 wt%), resulting in an obvious reduction of the DC breakdown strength.