Abstract
In the direct current electric field, the surface of epoxy resin (EP) insulating material is prone to charge accumulation, which leads to electric field distortion and damages the overall insulation of the equipment. Nano-doping is an effective method to improve the surface insulation strength and DC flashover voltage of epoxy resin composites. In this study, pure bismuth ferrite nanoparticles (BFO), as well as BFO nanofillers, which were doped by La element, Cr element as well as co-doped by La + Cr element, were prepared by the sol-gel method. Epoxy composites with various filler concentrations were prepared by blending nano-fillers with epoxy resin. The morphology and crystal structure of the filler were characterized by scanning electron microscopy (SEM) and X-ray diffraction (XRD) tests. The effects of different filler types and filler mass fraction on the surface flashover voltage, charge dissipation rate, and trap characteristics of epoxy resin composites were studied. The results showed that element doping with bismuth ferrite nanofillers could further increase the flash voltage of the composites. The flashover voltage of La + Cr elements co-doped composites with the filler mass fraction of 4 wt% was 45.2% higher than that of pure epoxy resin. Through data comparison, it is found that the surface charge dissipation rate is not the only determinant of the flashover voltage. Appropriately reducing the surface charge dissipation rate of epoxy resin composites can increase the flashover voltage. Finally, combining with the distribution characteristics of the traps on the surface of the materials to explain the mechanism, it is found that the doping of La element and Cr element can increase the energy level depth and density of the deep traps of the composite materials, which can effectively improve the flashover voltage along the surface of the epoxy resin.
Highlights
Composite insulators based on the epoxy resin (EP) have excellent electrical insulation and thermodynamic properties and are widely used in high-voltage power transmission equipment, such as gas-insulated switchgear (GIS) and large-scale pulse power devices [1,2,3]
The study found that the smaller the particle size of the filler, the lower the flashover voltage of bismuth ferrite nanoparticles (BFO)/EP composites
The flashover voltage of each EP composite material is higher than that of a pure EP system when the mass fraction of the nano-filler is less than 16%
Summary
Composite insulators based on the epoxy resin (EP) have excellent electrical insulation and thermodynamic properties and are widely used in high-voltage power transmission equipment, such as gas-insulated switchgear (GIS) and large-scale pulse power devices [1,2,3]. Nanomaterials 2021, 11, 2200 the electrode and gas–solid interface [8,9] These charges overflow the material surface under the action of the electric field, inducing surface flashover [10,11], which reduces the insulation reliability of equipment and even leads to insulation failure. For this reason, the researchers managed to improve the surface charge transport capacity of epoxy resin composites, accelerate the dissipation rate of surface charges, and increase the surface flashover voltage [12]. The explanation of flashover by trap theory still needs to be further improved, and the method of increasing the flashover voltage by adjusting the distribution of material traps needs in-depth study
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