Application of Surface Functionally Graded Materials for Solid Insulator in Gas Insulated Power Apparatus

Abstract

To uniform the electric field distributions and thus improve the flashover characteristics of insulators in AC gas insulated power apparatus, the concept of surface functionally graded material (SFGM) with a layer of designed permittivity ( $\boldsymbol{\varepsilon}$ ) distribution along the insulator surface is proposed in this paper. The magnetron sputtering technique was used to fabricate the $\boldsymbol{\varepsilon}$ -uniform insulator and the $\boldsymbol{\varepsilon}$ -SFGM insulator by depositing BaTiO 3 layers. Finite element simulations were employed to investigate the electric field distributions and leakage currents of different insulators. The results show that for the $\boldsymbol{\varepsilon}$ -uniform insulator, a larger thickness of the sputtering layer results in a more uniform electric field distribution but a higher leakage current. With the application of the $\boldsymbol{\varepsilon}$ -SFGM insulator, the maximum electric field strength and leakage current are both reduced compared to the $\boldsymbol{\varepsilon}$ -uniform insulator. Finally, experimental tests were conducted to verify the feasibility of SFGM. The AC flashover voltage of the $\boldsymbol{\varepsilon}$ -SFGM insulator is much higher than those of the conventional insulator and the $\boldsymbol{\varepsilon}$ -uniform insulator. Therefore, the $\boldsymbol{\varepsilon}$ -SFGM insulator has great potential for improving the reliability of AC gas insulated power apparatus.