Effect of Size and Content of SiO2 Nanoparticle on Corona Resistance of Silicon–Boron Composite Oxide/SiO2/Epoxy Composite

Abstract

Corona discharge always threatens the safe and long-term operation of electrical equipment. Therefore, it is imperative to improve the corona resistance of electrical insulation materials. In this research work, fumed silica (SiO2) with different particle sizes and self-made organic silicon–boron composite oxide (Si–B) are used to modify epoxy resin (EP) for enhancing the corona resistance. Si–B/SiO2/EP nanocomposites with different SiO2 content series and 4 kinds of SiO2 particle size series are prepared by grinding machine dispersing and thermal curing. A strong dependence of the corona resistance on SiO2 filler size in nano-scale and content is revealed experimentally. The filler combination of Si–B and nano-SiO2 can reduce the relative permittivity of the Si–B/SiO2/EP nanocomposites and inhibit the increase of dielectric loss. With the particle size of SiO2 filler increases, the space charge suppression effect and the thermal stability are reduced, but corona resistance life is improved.When the 15-nm SiO2 content is 15 wt%, the corona resistance life of the Si–B/SiO2/EP nanocomposites can reach 8.99 h under 90 °C and 80 kV/mm electric field strength, while pure epoxy is only 0.86 h. The degradation path through the material is the more important factor affecting corona resistance performance–large particle size and well dispersion state can effectively extend the degradation path through the material.