In order to investigate the impact of harmonic components on the insulation characteristics of epoxy resin materials used in dry bushing insulation under electro-thermal operating environments

multi-order harmonics superimposed with negative polarity DC bias voltage were used to simulate dry bushing operation waveforms. The effects of different harmonic components on the epoxy resin insulation degradation characteristics were investigated in the temperature range of 80~120 ℃. The results show that both harmonics and high temperature promote the insulation degradation of epoxy resins. The initiation voltage of epoxy resin degradation is reduced to 40.0%

and the insulation failure time of the specimens is reduced to 64.8% with the addition of a multi-order harmonic component to the electro-thermal operating environment. The harmonic components also lead to the expansion of the insulation deterioration area. The field-driven electrical tree growth model (FDTG) analysis shows that the intervention of higher-order harmonic components increases the electrical tree growth rate coefficient by 190.9%

and the electrical tree growth critical field strength is reduced to 17.88 kV/mm. Finally

the simulation results show that the material dielectric loss heating is intensified in the case of multi-harmonics addition

and the local overheating issue for long-term working equipment needs further attention.