Surface charge transport behavior and flashover mechanism on alumina/epoxy spacers coated by SiC/epoxy composites with varied SiC particle size

Abstract

Charge accumulation phenomenon on gas–solid interface greatly restricts the development of HVDC energy transmission system. In this study, the surface charge transport behavior and flashover performance on alumina/epoxy spacer coated by SiC/epoxy composites are experimentally investigated under DC stress. SiC/epoxy composites with varied SiC particle size are fabricated and deposited on spacer surface. Nearly a charge free surface is achieved especially at smaller SiC particle size, even when metallic wires are adhered on spacer surface and connected to high voltage electrode. The DC flashover voltage increases with the decrease of SiC particle size. On the one hand, smaller SiC particle size exhibits more outstanding nonlinear conductivity characteristics, contributing to accelerating charge dissipation, whereas on the other hand, it would introduce plenty of shallow traps due to the increased interfacial regions between SiC particle and epoxy matrix, resulting in aggravating charge accumulation. A theoretical model is proposed to reveal the control mechanism of SiC/epoxy coating with different SiC particle size on flashover performance. The validity of this model can be confirmed based on the surface trap distribution, carrier mobility and our previous investigations on gas–solid interface flashover development process.

Review of interface tailoring techniques and applications to improve insulation performance

“…As described above, chemical modification methods such as fluorination and plasma treatment can increase surface conductivity and promote charge dissipation, thereby increasing flashover voltage [14,15,[21][22][23][24]. Another effective method is depositing non-linear composite coating filled with a high concentration of semi-conductive fillers such as SiC or ZnO [33][34][35]. Du et al and Zhang et al investigated the effects of non-linear coating on surface charge behaviour and flashover voltage [33][34][35].…”

“…They found that the non-linear coating increases the charge carrier mobility, which suppresses charge accumulation and decreases the possibility of occurrence of effective electrons, as shown in Figure 11a. Moreover, the electric field-dependent non-linear conductivity properties of the non-linear coating can homogenise the surface electric field, thus hindering the propagation of surface streamer and contributing to improvement in the flashover voltage [35], as shown in Figure 11. The physical properties and geometric distribution of fillers have a substantial effect on surface conductivity and flashover voltage, so they should be carefully selected when designing the composite coatings.…”

“…Another effective method is depositing non-linear composite coating filled with a high concentration of semi-conductive fillers such as SiC or ZnO [33][34][35]. Du et al and Zhang et al investigated the effects of non-linear coating on surface charge behaviour and flashover voltage [33][34][35]. They found that the non-linear coating increases the charge carrier mobility, which suppresses charge accumulation and decreases the possibility of occurrence of effective electrons, as shown in Figure 11a.…”

Simultaneous Optimization of the Surface Hydrophobicity and Surface Charge Distribution of Insulating Materials

“…The trap distribution (including trap level and density) and conductivity (including surface and bulk conductivity) are closely related to the accumulation and dissipation of the surface charge. [38,39] The trap level and conductivity were measured to investigate the effects of the coating on the surface charge distribution. Isothermal surface potential decay (ISPD) is an effective method for determining the trap parameters of polymer insulation materials.…”

Gas–solid interface charge tailoring techniques: what we grasped and where to go

“…β-SiC ring-clad insulators with different doping contents (15%, 20%, and 25%) were prepared and DC surface flashover voltage in the medium of 10% to 90% SF6 / N2 mixed gas at 0.1MPa was tested. Then J. Xue et al turned their attention to the influence of SiC particle size in SiC/epoxy coating [70]. As shown in Figure 30, the results showed that surface charges are significantly suppressed by SiC/epoxy coatings, especially using smaller SiC particle size.…”