Electrical tree degradation of MgO/epoxy resin composites at different voltage frequencies

Electrical tree degradation is one of the main causes of insulation failure in high-frequency transformers. Electrical tree degradation is studied on pure epoxy resin (EP) and MgO/EP composites at frequencies ranging from 50 Hz to 130 kHz. The results show that the tree initiation voltage of EP decreases, while the growth rate and the expansion coefficient increase with frequency. Moreover, the bubble phenomenon at high frequencies in EP composites is discussed. Combined with trap distribution characteristics within the material, the intrinsic mechanism of epoxy composites to inhibit the growth of the electrical tree at different frequencies is discussed. It can be concluded that more deep traps and blocking effect are introduced by doping nano-MgO into EP bulks, which can improve the electrical tree resistance performance of EP composites in a wide frequency range.