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Voltage Distribution Design of a Novel 363 kV Vacuum Circuit Breaker

This paper presented a novel 363 kV/5000 A/63 kA vacuum circuit breaker (VCB) and its detailed hexa-break structure. The circuit breaker consists of 12 40.5 kV vacuum interrupters (VI) in each phase, and employs SF6 gas as the insulation. The whole apparatus is enclosed in an aluminum tank with 0.4 MPa SF6 gas. The vacuum interrupter works with phase selection control system and its moving contact is driven by the electromagnetic repulsion mechanism. To determine its static voltage distribution, a 3D FEM model is established to calculate the electric field and voltage distribution of each break at open state. Results show that the voltage distribution is uneven, and the first break share the most of voltage about 86.3%. Its maximum electric field is 18.9 kV/mm which would contribute the failure of breaking the short current. Meanwhile, the distributed and stray capacitance parameters of proposed arrangements are calculated based on the presented FEM model. Based on the distributed capacitances parameters, the equivalent circuit simulation model of the circuit breakers at open state is established in PSCAD. Finally, the influence of the grading capacitor on the voltage distribution of each break is discussed and optimal value of grading capacitors for the 363kV hexa-break VCB is confirmed to be 10nF.