Surface FGM Insulator Based on BaTiO3 Magnetron Sputtering for Electric Field Grading of AC Gas Insulated Power Apparatus

Electric field optimization is a critical technique to ensure the compact structure and reliable operation for AC gas insulated power apparatus. To obtain a more uniform electric field distribution, this paper proposes the concept of the
$d$
-SFGM insulator, i.e., applying the surface functionally graded material (SFGM) with a designed thickness (
$d$
) distribution of high permittivity along the insulator surface. The magnetron sputtering technique was used to fabricate the
$d$
-uniform insulator and the
$d$
-SFGM insulator by depositing BaTiO
₃
layers. The theoretical analysis indicates that the electric field distribution is optimized using the d-SFGM insulator, followed by the
$d$
-uniform insulator. The finite element simulations were employed to investigate the electric field distributions and dielectric losses of different insulators. The results show that for the case of the
$d$
-uniform insulator, a higher permittivity or larger thickness of the sputtering layer results in a more uniform electric field distribution. With the application of the
$d$
-SFGM insulator, the maximum electric field strength and dielectric loss are both significantly reduced compared to the
$d$
-uniform insulator. Finally, experimental tests were conducted to further verify the feasibility of SFGM. The AC flashover voltage of the
$d$
-SFGM insulator is much higher than those of the conventional insulator and the
$d$
-uniform insulators. Therefore, the
$d$
-SFGM insulator has great potential for improving the reliability of the AC gas insulated power apparatus.