Effect of Functionally Graded Material of Spacer with Contaminating Particle on Breakdown Voltage inside Gas Insulated Bus Duct

Abstract — For the enhancement of insulation reliability and the compact design in gas insulated power equipment, the solid insulators play crucial role of electrical insulation. In order to improve the insulation performance of the solid insulators, we should consider the following two technical points. Firstly, we have to improve the insulation performance of solid dielectrics itself. The second is the control of the electric field distribution in and around the solid insulating spacers. In this paper, we have proposed a new concept for spacer insulation; an application of a functionally graded material (FGM). We investigated the applicability of FGM for reducing the electric stress on triple junction point, which was one of the important factors dominating a long-term insulating property of the solid. Finite Element Method (FEM) has been used throughout this work, for its favorable accuracy, to calculate the electric field distribution inside gas insulated bus duct (GIBD). The electric field distribution around earthed particle contamination which adhered to uniform and FGM of disc-spacer is studied. Electric field relaxation effect (EFGM / Euniform) by introduction of the U-shape FGM spacer is also studied. The breakdown voltage calculations in case of gap with particles contamination are studied. The effect of gas pressure, SF6-gas concentration in various mixtures and the particle dimension (length and hemi-spherical radius) on the breakdown voltage are also studied. Finally, the effect of FGM of spacer on breakdown voltage i