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 <inline-formula> <tex-math notation="LaTeX">$d$ </tex-math></inline-formula>-SFGM insulator, i.e., applying the surface functionally graded material (SFGM) with a designed thickness (<inline-formula> <tex-math notation="LaTeX">$d$ </tex-math></inline-formula>) distribution of high permittivity along the insulator surface. The magnetron sputtering technique was used to fabricate the <inline-formula> <tex-math notation="LaTeX">$d$ </tex-math></inline-formula>-uniform insulator and the <inline-formula> <tex-math notation="LaTeX">$d$ </tex-math></inline-formula>-SFGM insulator by depositing BaTiO<sub>3</sub> layers. The theoretical analysis indicates that the electric field distribution is optimized using the d-SFGM insulator, followed by the <inline-formula> <tex-math notation="LaTeX">$d$ </tex-math></inline-formula>-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 <inline-formula> <tex-math notation="LaTeX">$d$ </tex-math></inline-formula>-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 <inline-formula> <tex-math notation="LaTeX">$d$ </tex-math></inline-formula>-SFGM insulator, the maximum electric field strength and dielectric loss are both significantly reduced compared to the <inline-formula> <tex-math notation="LaTeX">$d$ </tex-math></inline-formula>-uniform insulator. Finally, experimental tests were conducted to further verify the feasibility of SFGM. The AC flashover voltage of the <inline-formula> <tex-math notation="LaTeX">$d$ </tex-math></inline-formula>-SFGM insulator is much higher than those of the conventional insulator and the <inline-formula> <tex-math notation="LaTeX">$d$ </tex-math></inline-formula>-uniform insulators. Therefore, the <inline-formula> <tex-math notation="LaTeX">$d$ </tex-math></inline-formula>-SFGM insulator has great potential for improving the reliability of the AC gas insulated power apparatus.

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