Optimization technique for electrical insulation design of vacuum interrupters

Because of the excellent high insulation performance, vacuum is expected to be one of the alternatives of SF₆ gas. In order to reduce the use of SF₆ gas in substation equipment, the applicability of vacuum circuit breakers (VCB) and vacuum interrupters (VI) should be extended to higher (typically 145-300 kV) voltage. For the high voltage VI, the role of electrical insulation design becomes more important. For accurate insulation design of the VI, we developed an optimization technique to improve the electrical insulation performance. We evaluated several design variables necessary for optimizing the electrode contour of the main contactor and center shield in VI. The electrode area effect on vacuum breakdown characteristics as well as the electric field distribution was considered in the optimization process. In order to verify the accuracy and the efficiency of the proposed technique, we applied it to a practical model of VI. In addition, we examined the influence of the parameters of the area effect, arrangement of VI in VCB on the optimization result. From the calculation results, we confirmed that the optimization based on the area effect had higher availability and higher accuracy than the electric field optimization from the viewpoint of the improvement of the electrical insulation performance of vacuum insulated equipment.