Distribution of Polymer Surface Charge under DC Voltage and its Influence on Surface Flashover Characteristics

This study investigates the characteristics of polymer surface charge and their influence on DC surface flashover, which is significant to the study of surface discharge theories and the insulation design of high-voltage direct current equipment. Silicone rubber (SiR), epoxy resin (EP), and polymethyl methacrylate (PMMA), were selected as experimental materials in this paper. Using the active capacitance probe method, the charge accumulation, and dissipation characteristics of the polymers were studied under needle-plane electrode corona discharge. In cases of no surface charge accumulation, DC flashover tests were conducted in multiple electric fields. Furthermore, the influence of surface charge on flashover performance was quantitatively evaluated by means of optical and electrical tests as well as mathematical analysis. The results indicate that the surface potential of EP and PMMA increases more prominently as the applied voltage increases, but SiR is the least to do so. On the other hand, the surface potential of SiR and PMMA decays faster, with EP as the slowest of all. After the polymer accumulates surface charges, the flashover voltage, the luminance of the flashover arc channel, and the fractal dimension of the arc path all decrease. Besides, the flashover voltage of PMMA is extremely sensitive to surface charge, and the flashover voltage under extremely non-uniform electric field is less sensitive than that under the slightly non-uniform electric field. The analysis suggests that the surface charge exerts an influence on the flashover characteristics by affecting the surface field intensity and the surface discharge development process, and these factors ultimately determine the flashover characteristics.