Multi-dimensional functionally graded insulator for HVDC compact gas insulated apparatus

Abstract

Gas insulated switchgear (GIS) may be exposed to AC-DC mixed voltages in bipolar high voltage direct current (HVDC) systems. To improve the insulation performance of the epoxy insulator, this paper develops the multi-dimensional functionally graded materials (MFGM), which combines the bulk permittivity graded materials (ε-FGM) and the surface nonlinear conductivity materials (SNCM). The ε-FGM bulk and the SNCM layer of the MFGM insulator were prepared by the layer-by-layer pouring method and the air spraying technology. Results show that the electric field strength of the MFGM insulator around the HV triple junction is reduced by over 37% and 39% under AC and DC voltages. Compared with the uniform insulator, the AC and the DC flashover voltages of the MFGM insulator are raised by 17.5% and 27.5%, respectively. The MFGM insulator can adapt to both stationary and transient conditions, and thus has a promising application in HVDC compact gas-insulated apparatuses.