Basin-Type Spacer for DC-GIL—Part II: Surface Charge and Electric Field Regulation

This study discusses the approach of adaptatively regulating the surface charge and electric field distributions by nonlinear conductivity materials. Three groups of surface nonlinear conductivity (SNC) spacers, namely, SNC30, SNC60, and SNC90, were prepared by coating the epoxy (EP)/Al
₂
O
₃
spacers with EP/SiC composites of 30-, 60-, and 90-phr doping contents. Based on a downsized direct current gas-insulated transmission line (dc-GIL) model, the regulation effects of the SNC spacers are verified by changing the voltage waveforms and temperature gradients in both simulation and experimental studies. Results show impressive abilities of the SNC spacers on relaxing the electric field distortion by adaptively regulating the surface charge accumulation through nonlinear surface conduction. Under dc stress, the SNC spacers can significantly increase the discharge inception and the flashover voltages at room temperature. As the temperature gradient increases, the discharge suppression effects of the SNC spacers weaken first and then increase. Surface charges on the SNC60 and SNC90 spacers can make a rapid adjustment along with the polarity reversal voltage; the corresponding flashover voltages are improved by 18% and 29% compared with that of the original spacer.