Optimization design of bushing of distribution switchgear equipment

The compact design has become the development direction of power distribution switchgear equipment. As a key element of the power distribution switch, the electric field of high voltage bushing was concentrated. In order to enhance the overall reliability of the distribution switchgear, the insulation structure of the bushing needed to be optimized. This paper constructed the three-dimensional finite element model of a certain type of 10kV distribution switchgear. Simultaneously considered the uniform breakdown field strength and engineering breakdown field intensity of SF
₆
, determined the upper and lower limit of control field are 8850V/mm, 6500 V/mm as 1 minute power frequency withstand voltage of 42kV. The dielectric parameters of the switchgear were tested, then the electric field distribution inside the switchgear was simulated in finite element method(FEM), found that electric field was concentrated in these regions which were the air gap between bushing and flange, air gap between bushing and box and air gap between the central conductor limit and porcelain. Filling with semi-conductive adhesive, increasing the chamfer radius of conductor limit and using semi-conductive coating were adopted respectively in switch insulation structure optimization. The electric field distribution after optimization was simulated in FEM, results showed that electric field intensity in the previous concentrated area has lowered than the control field, the overall insulation reliability of power distribution switchgear has improved.