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Vacuum circuit breaker (VCB) has a longer life and shorter opening time than SF(6) circuit breaker, but current single-break VCB cannot be applied in high-voltage power system directly. Here, a fast 363 kV multi-break VCB design is presented and its voltage distribution characteristic and stray capacitors are analysed. A three-dimensional finite-element model of modularised hexa-break VCB composed of 12 vacuum interrupter modules installed on three series connected platforms is developed to calculate the voltage distribution and distributed capacitances. The result shows that the voltage distribution is uneven, and the first break shares the 67.974% of the whole applied voltage. On account of distributed capacitances parameters, an equivalent capacitance model with PSCAD is built to discuss the voltage distribution characteristic at different grading capacitance values, and the optimal grading capacitance value is determined to 10 nF.

Multi-break vacuum circuit breakers (VCBs) are the most potential approach for applying VCBs to high voltage power system. However, it has higher thermal stability requirements than normal single break VCBs due to its complex structure and high rated current. In this paper, a novel 363 kV/5000 A/63 kA SF6 gas insulate (GI) VCB with series and parallel structure is proposed. To analyze its temperature rise, a 3D coupled electromagnetic-thermal-fluid model is established based on actual size and calculated by finite element method under rated condition, which enables prediction of the temperature distribution of the contacts of VCB and bus bar. In the numerical model, the vacuum chamber is modelled as solid material with temperature dependent effective thermal conductivity while skin effect, nonlinear property of conductor resistivity and turbulence model are taken into consideration. The simulation results show that the hot spot is the contacts of VCB with a temperature of 102.2 K, while the temperature of busbars reach at 92.3 K. In addition, the influences of contact resistance, short circuit current on the temperature rise are discussed. Finally, the simulation results are validated by temperature rise experiment on prototype. Using the proposed model, the temperature rise and hot spot area can be predicted in advance, which could finally facilitate the design and performance evaluation of the 363 kV GI-VCB.

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.

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 SF 6 gas as the insulation. The whole apparatus is enclosed in an aluminum tank with 0.4 MPa SF 6 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.

Using fault current limiter is one of the effective ways to solve the problem that short circuit current exceeds the standard in the electricity system. This paper presented an economical fault current limiter based on fast circuit breakers. After the basic principle structure, the control strategy and action logic are explained. Based on this, we analyzed the feasibility and economy in details. A new circuit structure of fault current limiter with artificial zero-crossing circuit was proposed, which will ensure that the current limited before the first peak arrives. It is more economical than superconducting, the flexible and the conventionally economical. This paper provides a reference for the development and manufacture of fault current limiters applicable to high voltage levels in engineering practice.