Static Voltage Sharing Design of a Sextuple-Break 363 kV Vacuum Circuit Breaker

Abstract

A balanced voltage distribution for each break is required for normal operation of a multi-break vacuum circuit breaker (VCB) This paper presented a novel 363 kV/5000 A/63 kA sextuple-break VCB with a series-parallel structure. To determine the static voltage distribution of each break, a 3D finite element method (FEM) model was established to calculate the voltage distribution and the electric field of each break at the fully open state. Our results showed that the applied voltage was unevenly distributed at each break, and that the first break shared the most voltage, about 86.3%. The maximum electric field of the first break was 18.9 kV/mm, which contributed to the reduction of the breaking capacity. The distributed and stray capacitance parameters of the proposed structure were calculated based on the FEM model. According to the distributed capacitance parameters, the equivalent circuit simulation model of the static voltage distribution of this 363 kV VCB was established in PSCAD. Subsequently, the influence of the grading capacitor on the voltage distribution of each break was investigated, and the best value of the grading capacitors for the 363 kV sextuple-break VCB was confirmed to be 10 nF. Finally, the breaking tests of a single-phase unit was conducted both in a minor loop and a major loop. The 363 kV VCB prototype broke both the 63 kA and the 80 kA short circuit currents successfully, which confirmed the validity of the voltage sharing design.

Special Issue “Selected Papers from the 2018 IEEE International Conference on High Voltage Engineering (ICHVE 2018)”

“…The fields of HV testing, HV measurements and HV equipment were covered by papers [14][15][16]. In [14], the authors developed a cable termination model to reduce the electric field at cable ends and prevent surface and external discharges during standardized overvoltage tests.…”

“…A novel 363 kV/5000 A/63 kA sextuple-break vacuum circuit breaker (VCB) with a series-parallel structure was presented in [15]. The calculations of the voltage distribution and the electric field of each break at the fully open state via a 3D FEM model highlighted an uneven distribution of the applied voltage, with above 86% stressing the first break.…”

Design and short‐circuit current breaking test verification of a 72.5 kV single‐break fast vacuum circuit breaker

“…Thus, it enables the FVCB to reduce the fault elimination time from 50-60 ms to 20-30 ms. At present, the highest voltage level of the single-break FVCB is 40.5 kV, and the maximum breaking current is 40 kA rms , which cannot be applied directly to the transmission lines [21,22]. In order to develop FVCBs towards transmission voltage, multiple-break series-connected technology could be used: like a 126 kV FVCBs [23] uses 2 series-connected 40.5 kV breaking units; a 252 kV bus-coupling FVCBs [24] uses 4 series-connected 40.5 kV breaking units; the 363 kV FVCBs [25] uses 6 series-connected 40.5 kV breaking units. For multiple-break circuit breakers, the increase of break number will lead to an increase in cost and volume, and significant decrease in operating reliability.…”