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.
Highlights
63 kA and the 80 kA short circuit currents successfully, which confirmed the validity of the voltage sharing design
Modern power systems have a high requirement for switching appliances, which are essential for the safe and reliable operation of power systems
Our goal was to determine the value of the grading capacitor for a novel 363 kV sextuple-break vacuum circuit breaker (VCB) taking into account its gas-insulated scheme and series-parallel layout
Summary
Modern power systems have a high requirement for switching appliances, which are essential for the safe and reliable operation of power systems. As an important part of electrical switchgear, the vacuum switch plays an important role in controlling and protecting electrical power systems [1]. Vacuum interrupters have the advantages of environmental friendliness, fine extinction capability, and long lifespan [2]. Vacuum circuit breakers (VCBs) are widely applied in 40.5 kV and lower voltage power systems, while for 126 kV and higher voltage power systems SF6 circuit breakers are mainly used. Modern power systems have larger loads, which have higher requirements of power quality and safety. Short circuit currents should be interrupted instantly to reduce losses [3]
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