Research on insulation characteristics of multi-break in series extra high voltage vacuum circuit breaker

Multi-break in series is the measurement applied in the design of the extra high voltage vacuum circuit breakers (EHV VCBs). Because of the existence of the coupling and transient variation of the multi-physical fields, the multi-break in series is the uniformed large space-time field system covering the multiple physical parameters. And the insulation performance for each break in the series system change a lot than one break case, and the investigations on the unknown factors are necessary. Based on the application of the EHV VCB applied in the system, the dynamic insulation coordination property covers the dynamic insulation of each break and the design of the multi-break in series. In this paper, the 3D electric field of the triple-break vacuum interrupter (VI) in series is numerically simulated using finite element method (FEM). And the location of the maximum electric field strength and the field distribution along the surface of the movable and fixed contact are calculated and figured out. By the comparative analyses with different insulation structures in series, the variations of the electric field strength are obtained and illustrated. Moreover, by introducing the shielding covers and parallel capacitors, the design of each 72.5 VI unit is accomplished and the insulation property of the 220kV triple-break in series EHV VCB is analyzed.