Improved Electric Field Distribution Within Bushing Insulation by EP/GO Nanocomposites With Reduced Temperature Coefficient of Conductivity

Abstract

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 the reduced temperature coefficient of conductivity is proposed and investigated in this paper. DC conductivity of EP/GO nanocomposites with different loadings of 0, 0.05, 0.1 and 0.5 wt% at various temperature are investigated. Trap level distributions are characterized by the isothermal discharge current (IDC) method to clarify the conduction mechanism. Obtained results show that more shallower traps are introduced and the thermal activation energies of the nanocomposites are reduced by the GO nanoparticles, indicating that the temperature coefficient of conductivity of the nanocomposites is reduced. The improvement of electric field distribution within the bushing insulation under operating voltage is verified when the EP/GO nanocomposite with an appropriate content is 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. INDEX TERMS Valve-side bushing, electric field regulation, temperature coefficient of conductivity, graphene oxide, epoxy-based nanocomposites.

Synergistic effect of positive temperature coefficient and thermally conductive micro‐nano fillers on electrical and thermal properties of epoxy resin

“…17 Preventing the reduction in electrical resistivity and improving thermal conductivity as the temperature rises is crucial for polymeric insulating materials, and this can be tackled by incorporating standard fillers like Al 2 O 3 , MgO, and graphene oxide, which inhibit the movement of charge carriers at high temperatures. [18][19][20][21] Moreover, surface treatment of polymeric insulating materials has the potential to reduce the charge injection, thereby achieving higher electrical resistivity at elevated temperatures. [22][23][24] But the primary focus of these researches was to improve the electrical resistivity at high temperatures, with less emphasis on suppressing the NTC effect of EP resin.…”

Electrical resistivity‐temperature characteristics enhancement of insulating cross‐linked polyethylene composites by incorporating positive temperature coefficient particles with different Curie temperatures

“…Under direct current (DC) voltages, the electric field distribution is mainly determined by electrical resistivity. The electric field can be severely distorted as the electrical resistivity of XLPE decreases several orders of magnitude at operating temperature, which accelerates ageing and even causes insulation failure [8][9][10][11]. Therefore, it is essential to suppress the NTC effect in XLPE materials for the safe operation of HVDC cable.…”

Temperature Segment Compensation Method of Dissipation Factor for Insulation Diagnosis in Converter Transformer Bushing

“…It would be a feasible scheme that RIP bushings could at least a partial substitute for the oil-impregnated paper bushings in converter transformer for avoiding exposure of oil leakage, fire and explosion. However, in recent years, the insulation faults of RIP bushing in converter transformers have occurred frequently [5], which would pose a serious threat to the safety operation of power grid. It became the focus issues that accurately diagnosed the insulation status of RIP bushings.…”