Mechanism of ozone-improved surface flashover performance of epoxy composites

Surface flashover is a serious threat to the stable operation of advanced electrical applications. Ozone modification has recently been developed for improving the surface flashover performance. However, the effect of ozone on surface properties is still not fully elucidated. In this work, various concentrations of ozone are used to modify epoxy composites and their DC flashover voltages in SF6 at 0.1 MPa are evaluated. The results show that the flashover voltage of sample modified by 130 mg/L ozone for 4 h is improved by 22.6%, from 31.29 kV to 38.35 kV. It is proved to be highly related to the surface chemistry and trap properties. The X-ray photoelectron spectroscopy (XPS) spectra shows that some C-H and C--C bonds on the surface are oxidized to C-O and C--O bonds. The results of simulation and surface trap demonstrate that the oxidized C-O and C--O bonds change the frontier orbitals and density of states, thus leading to a lower deep trap density. The lower trap density alleviates the generation of electron avalanche and eventually improves the flashover voltage. This work reveals the mechanism of ozone modification improving surface flashover voltage and provides a promising route to enhance the surface flashover performance.