Electric field calculation and shield optimization for 1000kV GIS bushing

Bushing used for gas insulated switch-gears is a key equipment in GIS, which mainly uses SF6 as its insulating material. The electric field strength inside the bushing and at the surface of the bushing sheath could significantly influence the safety and stable operation. Firstly, the model of a 1000kV bushing inflated with SF6 is built. Finite element analysis is adopted to calculate the distribution of electric potential and electric field strength. Additionally, the electric field strengths of several pivotal positions of the bushing are compared between single-layer shield structure and double-layer shields structure. The double-layer shields structure which UHV bushings usually adopt could lower the electric field strength inside the bushing and at the surface of the bushing sheath. Furthermore, the height of the shield, radius of the turn-up at the top of the shield, the size and location of the grading ring are optimized. Conclusions are listed. The bushing that the paper researches on has passed all type tests. The conclusions of this paper could provide theoretical guidance for the structure design of GIS bushings.