Simulation on discharge inception voltage improvement of GIS spacer with permittivity graded materials (ε-FGM) using flexible mixture casting method

For electric field grading in GIS spacers, the application of functionally graded materials (FGM) with spatial distribution of dielectric permittivity (ε) can be one effective solution. In this paper, we propose the flexible mixture casting (FMC) method as a novel and practical technique to fabricate ε-FGM for GIS spacers. We verified that the relative permittivity (er) can be controlled from ε_r = 4 to ε_r = 30 by varying the loading ratio of high permittivity filler particles under the FMC method. Toward the practical application of ε-FGM, we verified the relaxation effect of maximum electric field strength and the improvement effect of discharge inception voltage in SF₆ gas in a simplified GIS spacer model using ε-FGM under the FMC method. Simulation results revealed that the maximum electric field strength can be effectively reduced and the discharge inception voltage can be significantly improved compared with using a constant and uniform permittivity.