Fabrication of Multidimensional Functionally Graded Insulator for HVDC GIS

Gas insulated switchgear (GIS) can encounter the voltage that combines both AC and DC components in a bipolar HVDC. systems. To enhance the insulation performance of the epoxy insulator, the researchers developed a new type of material called multi-dimensional functionally graded materials (MFGM). This material integrates two types of materials, namely the surface nonlinear conductivity materials (SNCM) and the bulk permittivity graded materials ($\varepsilon-\mathbf{F G M}$). The MFGM insulator consists of SNCM layer and $\varepsilon-\mathbf{F G M}$ bulk, which were produced through air spraying technology and layer-by-layer pouring methods. Results indicate that the MFGM insulator reduces the electric field intensity around the HV triple junction by more than 37% and 39% under AC and DC voltages, respectively. Furthermore, the MFGM insulator also raises the flashover voltages under AC and DC voltages by 17.5% and 27.5%, respectively, compared to a uniform insulator (U-insulator). The MFGM insulator can work under both stationary and transient conditions and shows potential for use in HVDC compact gas-insulated apparatuses.