Nano SiO2/epoxy coating effect on lighting impulse breakdown characteristic in N2

Abstract

Since SF6 has a very high global warming potential, it is essential to replace SF6 with environmentally friendly insulation gas. However, most readily available insulation gases have low electrical breakdown strength, which needs to adopt additional insulating means to enhance the poor breakdown strength. In this paper, with the aim of improving breakdown strength, filler/epoxy (EP) composites with nano-SiO2 particles in the weight percentage range of 0–5 wt% are used as dielectric coating materials and N2 is applied as insulating gas. As compared to that of neat EP, there is a decline in permittivity of SiO2/EP nanocomposites in the frequency range from 10–2 to 106 Hz. Moreover, for SiO2/EP nanocomposites, the permittivity increases at first and then decreases as the filler content increases. With respect to the gas-coating insulation system, 50% breakdown voltage (BDV) U50 of the electrode with pure EP dielectric coating material is larger than that of bare electrode. Furthermore, a better BDV performance is obtained when applying SiO2/EP nanocomposites as dielectric coatings, indicating the introduction of SiO2 nanoparticles into EP matrix can reinforce the property of epoxy. The maximum BDV of 93 kV occurs in the electrode with 3 wt% SiO2/EP coating material, which is 29.17% higher than that of bare electrode. Additionally, it is found that the permittivity of coating material has a significant influence on the breakdown performance since it can alter the electric field distribution, and a lower permittivity always gives rise to a higher BDV.