Multi-break Vacuum Circuit Breaker Research Articles

Investigation of the dielectric recovery process of vacuum arc in double breaks by planar laser-induced fluorescence

The multibreak vacuum circuit breaker uses multiple short gaps to interrupt the fault current, greatly improving the dielectric strength, and is a viable method to realize high-voltage interruption. The metal vapor distribution near the current zero is crucial for the dielectric recovery process in the multibreak vacuum circuit breaker. Due to the complicated dielectric construction and the interaction between the breakers, the vacuum arc inevitably deviates from the axisymmetric distribution during the interruption process. The traditional diagnosis method limited to 0D or 1D is not sufficient to study the real distribution of metal vapor near the current zero. To address these issues, we developed a planar laser-induced fluorescence method to measure the 2D distribution of copper vapor near the current zero by detecting 510.6 nm fluorescence intensity. The results indicate that for the butt contacts, the copper vapor is diffused in the gap of the high-voltage break and aggregated on the cathode surface of the low-voltage break. The axial magnetic field and transverse magnetic field affect the 2D copper vapor distribution and eliminate the inconsistency, which is achieved by affecting the motion of charged particles and the ionization-recombination process. Furthermore, the copper vapor density exhibits a positive dependence on the arc current, and the magnetic field impacts the density increase rate and distribution mode.

Influence of the vapor shield potential control on the post-arc sheath development in vacuum interrupters

In tank-type multi-break vacuum circuit breakers (VCBs) and gas-insulated switchgear (GIS), the non-uniform distribution of vapor shield potential in the vacuum interrupters impacts the post-arc process significantly. To explore the effect of the vapor shield potential on the development of the post-arc sheath, a particle-in-cell model with shield potential control is proposed to obtain two-dimensional distributions of post-arc particles. Based on the synthetic test circuit and probe array, the test platform of the post-arc characteristic diagnostic is set up to verify the influence of vapor shield potential distribution on the post-arc sheath. The extinguishing process of the vacuum arc is also observed by the high-speed CMOS camera. Simulation and experimental results show that at shield potential of 0.5 transient recovery voltage, the post-arc sheath develops most rapidly and the distribution of cathode spots is the most uniform. These findings can provide valuable insights for the design of vacuum interrupters and the control of shield potential in tank-type GIS.

Electromagnetic-thermal-flow field calculation and optimal design of environment-friendly live tank multi-break vacuum circuit breakers

Electromagnetic-thermal-flow field calculation and optimal design of environment-friendly live tank multi-break vacuum circuit breakers

Analysis of motion characteristics and synchronous error based on vacuum switch module with integrated operation of double-break

Multi-break vacuum circuit breakers (VCBs) is an important research direction for scaling VCBs up to a higher voltage level. A VCB module with an integrated operation of double-break is designed to increase synchronization of multi-break VCBs, and the synchronization error beyond the mechanical structure is eliminated. First, the mathematical model and motion model of the transmission system were established. Then the motion characteristics and the double-break synchronization error of the module were analyzed. Finally, the prototype was designed and manufactured for parameter testing and trajectory verification. The analysis shows that the displacement transmission ratio increases with the increase in the transmission pull rod length and the initial closing angle. The length of the transmission pull rod has little effect on the displacement transmission ratio, while the initial closing angle has a major effect on it. The simulation results show that the transmission system can realize maximum control of the double-break mechanical error to within 0.59 mm with the IT12 level and the mechanical error obtained by the root sum squared method can be within 0.3 mm. The maximum mechanical error can be controlled to within 0.06 mm by improving the tolerance and fit of moving pairs to the IT6 level. The experimental results reveal that the maximum mechanical error of double-break’s clearance between open contacts is 0.49 mm and the synchronization error is not greater than ±0.1 ms. It is proved that the module can realize high precision synchronous operation. This study provides a practical design idea and processing requirements for the control of synchronous errors of multi-break VCBs.

Prediction Method of the Breakdown Probability for Multiple Vacuum Gaps in Series Considering Dielectric Recovery under a Lightning Impulse Voltage

The objective of this article is to propose a novel prediction method of the breakdown (BD) probability for multiple vacuum gaps (VGs) in series considering their dielectric recovery under a lightning impulse voltage. Based on the experimental data of the BD probability for each single VG and the calculated voltage distribution of multiple VGs, the BD probability of multiple VGs in series could be calculated by the proposed prediction method. By dielectric tests under the lightning impulse voltage, we see that the calculated BD probability distributions fit well with the experimental results for double VGs and triple VGs in series. Under sphere–plane electrode VGs, the prediction error was approximately 15% in the whole range of BD probabilities. The errors of the 50% BD voltage were 11.4% and 12.9% for double VGs and triple VGs in series, respectively. Therefore, the reliability of this prediction method considering the dielectric recovery was validated. This prediction method could be used to estimate the dielectric strength of multibreak vacuum circuit breaker (VCB) and multiple floating shields inside high-voltage vacuum interrupters.

Simulation Research on the Post-arc Dielectric Recovery Characteristics of Multi-break Vacuum Circuit Breakers

The dielectric recovery characteristics are very important for the successful interruption of the vacuum circuit breaker. In order to explore the influence of the post-arc dielectric recovery characteristics of the multi-break vacuum circuit breaker on its breaking, this article establishes a simulation model of the multi-break vacuum circuit breaker and a 750kV short line fault simulation circuit in MATLAB. By adjusting the dielectric recovery characteristics of different breaks, the critical dielectric recovery rate (The minimum dielectric recovery rate of the break when the circuit breaker does not break down) under different conditions is finally obtained. In addition, the influence of the equalizing capacitor on the critical recovery rate is also explored. It is found that the smaller the grading capacitance, the greater the voltage of the break, and the greater the critical dielectric recovery rate.

Investigation on the Influence of Different External Magnetic Field Strength on the Dynamic Voltage Distribution of Double-Break Vacuum Gaps in Series

Previous researches show that grading capacitors truly improve the dynamic voltage distribution uniformity of multibreak vacuum circuit breakers (VCBs). However, large capacitors can reduce the breaking capacity. In order to obtain balanced voltage distribution with small capacitors, nonsynchronous external magnetic field was adopted. The Helmholtz coil was designed to generate a stable magnetic, and nonsynchronous magnetic field control system was designed to realize double-break nonsynchronous control. The 3-D models of Helmholtz coil and axial magnetic field (AMF) contact were simulated and analyzed in Maxwell. The external magnetic field (EMF) experiment platform for double-break vacuum gaps was set up. In the experiment, the strength of EMF on each break can be adjusted by the nonsynchronous magnetic field control system. The experimental results show that different EMF strengths on two vacuum breaks in series can improve the voltage distribution uniformity. Meanwhile, the magnetic field strength has the best matching parameters. The works in this article provide references for magnetic field regulation and interruption performance of VCBs.

Effect of Magnetic Field on Different Opening Processes of Multi-Break Vacuum Gaps

Vacuum gap saturation of single break can be solved by multiple breaks in series. In different breaking processes, the unbalanced energy and charges injected into the breaks lead to unbalanced voltage distribution. The purpose of this paper was to compare the voltage distribution under the regulation of magnetic field in different opening process. The magnetic fields with 3 ms width were applied at the point 3 ms before current through zero. Comparing with no axial magnetic field, the voltage distribution unbalances deceased both in synchronous and asynchronous opening processes. Under the condition that the arcing time of high-voltage break remained at 6.6 ms and the magnitude of axial magnetic fields was 60 mT, voltage distributions of high-voltage break were approximately proportional to the arcing times of the low-voltage break from 3.4 ms to 6.6 ms. It demonstrated that axial magnetic fields could effectively improve the voltage distribution of multi-break vacuum circuit breakers in synchronous and asynchronous opening processes.

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

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.

Investigation on the Thermal Performance of a 363 kV Vacuum Circuit Breaker Using a 3D Coupled Model

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 Review of the Synergy Effect in Multibreak VCBs

At present, multibreak vacuum circuit breakers (VCBs) have attracted more attention in order to meet the requirement of the environmental protection, high-voltage VCBs, capacitive current switch-off, and the dc current breaking. The advantages and disadvantages of multibreak VCBs are analyzed and discussed according to the research status. Then, the synergy effect of multibreak VCBs is proposed, which is the interaction among the arc memory, current zero characteristic, and the postarc characteristic. The target of the synergy effect is the synergy between the dynamic dielectric recovery strength and the postarc dynamic voltage distribution. The maximum breaking capacity can be obtained in the above-mentioned synergy control. Finally, the optimization design, key technology, basic theory, and application of multibreak VCBs are discussed. With the development of multibreak VCBs, it will be widely used in high-voltage level, HVdc, and pulsed-power switchgear in the future.

Mechanism of Dynamic Voltage Distribution in Series-Connected Vacuum Interrupters

This paper proposes the equivalent circuit of postarc dynamic voltage distribution (PDVD) in multibreak vacuum circuit breakers (VCBs). The equivalent circuit is composed of controlled postarc sources, postarc resistors, and equivalent capacitors. The sheath growth and the postarc process of double-break VCBs are analyzed. The PDVD is divided into four processes: the initial transient recovery voltage (TRV) process, the oscillating TRV process, the stable TRV process, and the power-frequency voltage process, which can be analyzed by the equivalent circuit. The novel equivalent circuit of the PDVD in multibreak VCBs is gained by introducing the controlled postarc current source. The test platform is set up in the synthetic circuit. The postarc current, grading capacitor current, and the TRV are measured to analyze the PDVD in the above four processes. The test results verify the theoretical analysis. Therefore, the mechanism of the PDVD in multibreak VCBs is obtained and described by the equivalent circuit, which is useful to gain even voltage distribution and improve the breaking capacity of multibreak VCBs.

Investigating influence of the magnetic arc blow in multi-break vacuum circuit breakers

This paper investigates the influence of the interactive magnetic field in multi-break vacuum circuit breakers (VCBs) on the arc plasma and the post-arc characteristics. The magnetic field of multi-break VCBs is asymmetric and off-center because of the interactive magnetic field, which is also called bias magnetic field (BMF). The BMF distribution of double-break VCBs is gained by electromagnetic analysis. The test circuit of the magnetic arc blow in multi-break VCBs is established by simplifying as the interaction between the vacuum arc and the BMF. The influence of the magnetic arc blow on the arc plasma is studied by the high-speed CMOS camera and the post-arc current measure. While the vacuum arc is in the direction of the Ampere force with the BMF at 200 mT, it is in the retrograde direction when the BMF is below 100 mT, which results in the post-arc charge obviously varying from 9 μC to 50 μC. The relationship between the BMF and the post arc charge is gained. The mechanism of the magnetic arc blow in multi-break VCBs is discussed. Therefore, this paper can provide the base of construct and configuration to avoid the influence of the magnetic arc blow.