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The hybrid dc circuit breaker (HDCCB) is one of the most promising solutions for the dc interruption. But the power electronics-based load commutation switch (LCS) in the main current path causes the high on-state loss and cost, which inhibits the application of the HDCCB. In this paper, a novel hybrid dc circuit breaker is proposed, in which the vacuum interrupter with the external transverse magnetic field (ETMF) is designed to improve the arc voltage and thus enhance the current commutation to power electronics. The ETMF-based vacuum interrupter achieves the fast current commutation instead of the LCS, which realizes the low on-state loss and cost while preserving the short commutation and interruption time. The arc voltage characteristic with ETMF is analyzed, and the influence of the different factors on the commutation time and di/dt before current zero are investigated in detail. Based on the calculation results, a 10 kV dc breaker prototype based on the proposed topology is developed with the breaking current of 15.5 kA. Finally, the application of the proposed scheme in HVdc grids is discussed. [ABSTRACT FROM AUTHOR]

High-voltage DC (HVDC) circuit breaker is the necessary equipment for multiterminal HVDC grids, which is a prospective power transmission method in the future. Therefore, the research about HVDC interruption ushered in an explosive development in recent years. The mechanical DC circuit breaker based on the precharged capacitor for current commutation and interruption is considered to be one of the most promising HVDC interruption solution. However, the commutation capacitor requires a complicated precharging circuit, especially in high-voltage applications, which brings a great challenge to the promotion of mechanical interruption solution. In this article, a novel self-charging mechanical HVDC circuit breaker is proposed. It utilizes the induced voltage generated by part of current limiting reactor to adaptively charge the commutation capacitor under different fault current conditions without extra auxiliary charging circuit. By investigating the influence of capacitance and inductance on the charging time and current commutation process, the optimized parameters are determined. Then, the breaking performance of proposed HVDC breaker under different rising rates of fault current is evaluated in a two-terminal HVDC system. Finally, a low-power prototype is developed to verify the feasibility of the proposed topology and an improved scheme for rated current breaking is discussed. [ABSTRACT FROM AUTHOR]

Medium-voltage dc (MVdc) distribution systems have the advantages of high power density, low line loss and fast system response. However, the high rise rate and large peak value of short circuit current make the fault current interruption a critical problem in MVdc systems. To solve this problem, a novel circuit breaker scheme based on integrated gate-commutated thyristor (IGCTs) current sharing integrated with freewheeling is proposed in this article, which not only can ensure a high breaking capacity and short interruption time in the full current range, but also have superior vacuum interrupter recovery performance and high breaking reliability. The analysis of key factors, including stray parameters, inductance-capacitance (LC) parameters and arcing time, on the current commutation characteristics is presented, and the optimal design principle of the circuit breaker parameters is obtained. Finally, the proposed MVdc circuit breaker is verified with a 64.2 kA/10 kV fault current interruption experiment. [ABSTRACT FROM AUTHOR]

DC circuit breaker plays an important role in the reliability of HVdc system, but the large number of expensive press-pack insulated-gate bipolar transistors (IGBTs) is used at present, which is a serious impediment to HVdc development. Thus, the low-price integrated gate commutated thyristor (IGCT) becomes a promising alternative device. This letter presents a low-cost HVdc circuit breaker with high current breaking capability based on IGCTs. The topology and principle of the proposed HVdc circuit breaker are introduced at first. Then, the parameter design is analyzed. A scaled-down test successfully demonstrates the high current breaking capability of 15 kA. In the end, the cost comparison shows that this scheme can achieve 61.8% cost reduction of the commutation branch. [ABSTRACT FROM AUTHOR]

The fault current limiting in high-voltage dc (HVdc) grids is critical to reducing the breaking stress of dc circuit breaker and improving the breaking reliability. However, the existing HVdc circuit breakers rarely consider the rapid limiting of fault current in the breaking process. In this article, a novel HVdc circuit breaker integrating current commutation and damping is presented, which can realize fast current limiting and interruption while preserving large breaking capability and low cost. Simulation analysis of current commutation capability is carried out to determine the optimal parameters in the current damping module. Then, the fault current breaking performance of the proposed HVdc breaker is evaluated and compared with conventional hybrid HVdc breaker theoretically. Finally, a low-power prototype of the current damping dc breaker is built and tested to verify the validity of the proposed topology. [ABSTRACT FROM AUTHOR]

The medium-voltage direct current (MVDC) distribution grids have been given significant attention because of their wide applications in the grid integration of the renewable energy sources and in the improvement of the stability and quality of the grid. However, due to the absence of the natural zero current crossings and the high rate of the short-circuit current, the fault current interruption in the MVDC systems is more problematic than that in the ac systems. Several types of interruption schemes have been proposed, and the vacuum interrupter-based dc circuit breaker (DCCB) is a promising solution for the MVDC interruption. Because of its high arcing current, the dielectric strength of the vacuum interrupter after the current crossing point stays low, which makes the dielectric recovery strength a critical factor for the reliability of the interruption. To estimate the reliability of the MVDC interruption, an experimental circuit is designed to measure the dielectric recovery strength of the vacuum interrupter, and the main influence factors are investigated with the experiments conducted under different arcing currents, contacts, di/Δ t before the current zero, and arcing times. The analysis and comparison of the dielectric recovery strength under different conditions are presented. The safe recovery time under different interruption conditions is proposed. [ABSTRACT FROM AUTHOR]

The medium-voltage direct current (MVDC) distribution grids have been given significant attention because of their wide applications in the grid integration of the renewable energy sources and in the improvement of the stability and quality of the grid. However, due to the absence of the natural zero current crossings and the high rate of the short-circuit current, the fault current interruption in the MVDC systems is more problematic than that in the ac systems. Several types of interruption schemes have been proposed, and the vacuum interrupter-based dc circuit breaker (DCCB) is a promising solution for the MVDC interruption. Because of its high arcing current, the dielectric strength of the vacuum interrupter after the current crossing point stays low, which makes the dielectric recovery strength a critical factor for the reliability of the interruption. To estimate the reliability of the MVDC interruption, an experimental circuit is designed to measure the dielectric recovery strength of the vacuum interrupter, and the main influence factors are investigated with the experiments conducted under different arcing currents, contacts, $di/{\Delta t}$ before the current zero, and arcing times. The analysis and comparison of the dielectric recovery strength under different conditions are presented. The safe recovery time under different interruption conditions is proposed. [ABSTRACT FROM AUTHOR]

The emerging demand on development of high-voltage direct current (HVdc) networks brings about an increasingly urgent need for a fast and reliable HVdc circuit breaker. This paper proposes a novel topology of HVdc circuit breaker combining a liquid metal load commutation switch and a two-stage commutation circuit, which offers an effective solution for isolating faults while preserving larger current breaking capability and lower overvoltage rate of rise. With the topology optimized in terms of circuit parameters for determining their optimum design values, the handling of short-circuit faults for the proposed circuit breaker in HVdc application is predicted theoretically. Finally, preliminary tests from a developed low-power prototype are presented together with a comparative simulation study provided to verify the performance of the proposed HVdc circuit breaker. [ABSTRACT FROM AUTHOR]

The radiation characteristics of thermal plasma columns filled with N2-polytetrafluoroethylene vapor mixture has been studied for the first time. The net emission coefficient is first calculated for typical mixture concentrations. The discrete ordinate method (DOM), which has proven to be an approximate method of reasonable accuracy for radiation transfer in thermal plasmas, is then used to characterize the emission and absorption behavior of cylindrical plasma columns with typical temperature distributions. Results show that the radiative power loss per unit volume at the column center is not always proportional to the local gas pressure. The DOM12-9 configuration, i.e., considering 24 directions in the $r$ -plane of the calculation point and 18 directions crossing the $r$ -plane, produces remarkably accurate results. It is likely to recover the accurate emission and absorption profile by scaling the output from the DOM5-3 configuration with a scaling factor between 0.7 and 0.8. Furthermore, the DOM5-3 configuration accurately locates the absorption layer at the edge of the plasma column. Maximum absorption takes place at a radial location whose distance to the inner radius of the absorption layer is 30% of the layer thickness despite of the very different radial temperature profiles. Under the conditions studied 35%–60% of the radiation from the central part of the column is absorbed in the surrounding cooler gas. [ABSTRACT FROM AUTHOR]

In this paper, the complicated arc phenomena in air dc circuit breakers that are widely used in rail transit and vessels are investigated with both experimental and numerical approaches. Initially, the basic arc motion characteristics in the switch are presented by the recorded waveforms and images in the carefully designed breaking experiments. Phenomena of arc stagnation and back commutation are revealed and the influence of arc chamber width on the arc stagnation is preliminarily discussed according to the experimental results. Then, to make the nature of arc motion clear and to determine the influence details of the arc chamber width on arc motion characteristics, a simplified model based on magnetohydrodynamics theory is built and four cases with the arc chambers of different widths are calculated. The simulated arc behavior is presented by the temperature distribution sequences. In addition, the formation process of back commutation is described in detail by the variation of arc column. The influence mechanism of arc chamber width on arc motion is analyzed according to the differences of pressure propagation and temperature distribution in the arc chamber. Furthermore, the calculated arc displacement curves show that the arc stagnation time could be shortened and the risk of back commutation could be reduced by decreasing the arc chamber width within the reasonable extent. [ABSTRACT FROM PUBLISHER]

Arc plasma behavior plays an important role on the performance of the low voltage air dc circuit breakers (DCCB). A 3-D arc model considering the turbulence effect for a large arc chamber of an air DCCB is built. The arc evolution is described in detail by the temperature distribution. [ABSTRACT FROM PUBLISHER]

Arc behavior is very important to the performance of a low-voltage circuit breaker. A 3-D arc model for a certain type of miniature circuit breaker is built and calculated in this paper. The arc evolution is described in detail according to the temperature distribution images from the simulation results. [ABSTRACT FROM AUTHOR]