Fabrication and electrical evaluation of interfacial E-field regulating insulator for DC-GIL application

To reduce the electric field (E-field) distortion in a gas-solid insulating system, this paper proposes a centrifugation technique to fabricate interfacial E-field regulating (IER) insulators. During the curing process of the liquid epoxy/SiC mixture in the mold, a centrifugal force was used to force the SiC particles to the insulator surface, forming a uniform surface layer with nonlinear conductivity. After fabrication, electrical evaluations, including electrical simulations and flashover tests, were conducted to verify the E-field regulating effect of novel insulators. As the surface layer thickness of the novel insulator increases, the maximum E-field strength in the flashover region declines and converges to a stable value, but the conduction loss continues growing in the surface layer. The E-field concentration in the flashover region can be greatly relaxed by these novel insulators with 0.1 and 0.25 mm surface layers. Flashover test results show that the novel insulators have better insulation performance than that of the conventional insulator under different voltage waveform applications, i.e., gradually increasing voltage, DC voltage superimposed with impulse voltage, and polarity reversal voltage. By applying such novel insulators, a higher reliability and compacter structure can be realized for the DC-GIL.