Direct Current Circuit Breakers Research Articles

Operation status monitoring for 500 kV DC circuit breaker with internal failures and relative backup fault isolation schemes

As the primary protection and control device in direct current (DC) power systems, DC circuit breakers (DCBs) have complex structures and numerous components, making it prone to diversified internal failures. This paper explores an operation status monitoring method for DCBs, and relative backup fault isolation schemes and system recovery schemes are proposed to handle cases of DCBs with different internal failures. Contributions of this paper are: (1) An operation status monitoring method is proposed to reflect the failure degrees of DCB, categorizing the statuses of DCB into status-1 (normal), status-2 (minor failure) and status-3 (major failure). (2) According to the failure degrees of DCB, relative backup fault isolation and system recovery schemes are proposed to ensure the fault isolation scope is as small as possible and the system could recovery as fast as possible. Simulations are conducted in PSCAD/EMTDC for validation.

Influence of external AC transverse magnetic field on air arc oscillation patterns and its application in DC forced current zero techniques

Abstract Direct current (DC) circuit breakers are essential for maintaining the stability of the electric energy transmission and safeguarding the power equipment from the damage caused by the fault currents in DC power systems. The characteristics of the switching arc can be utilized in DC forced current zero techniques. This paper investigates the influence of an external alternating current (AC) transverse magnetic field on the oscillation characteristics of air arc. By confining the arc between two insulating walls and applying a transverse AC magnetic field, the arc exhibits "bidirectional oscillation" and "unidirectional oscillation" modes. The effects of magnetic field amplitude and frequency on the air arc oscillation characteristics are analyzed through experiments, from the aspects of the arc voltages and arc motions. It can be found that an external AC magnetic field can stabilize the arc voltage at a specific oscillation frequency. By connecting an inductor-capacitor (LC) branch in parallel with the arc and setting the LC branch's resonant frequency equal to the arc voltage oscillation frequency, a current resonance process between the arc and the LC branch can be achieved. This resonance facilitates the creation of the arc current zero-crossing point. A test platform based on the arc oscillation characteristics is established for current interruption experiments. For system currents of 1 kA and 3 kA, the arc current zero-crossing time is controlled within 0.41 ms after applying the external AC transverse magnetic field. The experimental results verify the rationality of the proposed DC breaking scheme.

Study of arc and magnetic field parameters under delayed breaking condition of DB-DC VCB

Taking the mechanical double-break DC vacuum circuit breaker (DB DC VCB) as the research object, the magnetic field and temperature field distribution between the breaks and the plasma characteristics under the working condition of gap difference caused by actuator dispersion are investigated to explore the difference in arc characteristics between the two breaks. Based on the system of Maxwell and magnetohydrodynamic (MHD) equations, a non-simultaneous breaking model of the DB DC VCB is established, and parameters such as magnetic flux density, plasma velocity, inter-contact pressure, and ion and electron temperatures are calculated. The simulation results show that the cathode surface field emission effect is stronger in the small gap break (delayed breaking break). Besides, in the small gap break, the arc temperature is higher, the rate of decrease of temperature is lower, the electron velocity is higher, the magnetic flux density is lower, the regulatory ability of the magnetic field is weaker, and the plasma diffusion speed is slower. In the arc ignition stage, the arc aggregation state duration of the small gap break is longer than that of the normal break, which means the arc in the small gap break gets diffused and arc energy dissipation becomes harder. Therefore, the arc energy density of the delayed breaking break is greater, the arc morphology transition time is longer, the residual particle concentration after arc extinguishing is higher, and the probability of re-strike breakdown increases with the increase in gap difference. Improving the synchronization of the actuator could improve the breaking ability of the DB DC VCB. Index terms—plasma arc, double-break direct current vacuum circuit breaker (DB-DC VCB), transverse magnetic field (TMF), magnetohydrodynamic (MHD) model.

The Development of Bi-LSTM Based on Fault Diagnosis Scheme in MVDC System

Diagnosing faults is crucial for ensuring the safety and reliability of medium-voltage direct current (MVDC) systems. In this study, we propose a bidirectional long short-term memory (Bi-LSTM)-based fault diagnosis scheme for the accurate classification of faults occurring in MVDC systems. First, to ensure stability in case a fault occurs, we modeled an MVDC system that included a resistor-based fault current limiter (R-FCL) and a direct current circuit breaker (DCCB). A discrete wavelet transform (DWT) extracted the transient voltages and currents measured using DC lines and AC grids in the frequency–time domain. Based on the digital signal normalized by the DWT, using the measurement data, the Bi-LSTM algorithm was used to classify and learn the types and locations of faults, such as DC line (PTP, P-PTG, and N-PTG) and internal inverter faults. The effectiveness of the proposed fault diagnosis scheme was validated through comparative analysis within the four-terminal MVDC system, demonstrating superior accuracy and a faster diagnosis time compared to those of the existing schemes that utilize other AI algorithms, such as the CNN and LSTM. According to the test results, the proposed fault diagnosis scheme detects MVDC faults and shows a high recognition accuracy of 97.7%. Additionally, when applying the Bi-LSTM-based fault diagnosis scheme, it was confirmed that not only the training diagnosis time (TraDT) but also the average diagnosis time (AvgDT) were 0.03 ms and 0.05 ms faster than LSTM and CNN, respectively. The results validate the superior fault clarification and fast diagnosis performance of the proposed scheme over those of the other methods.

Analysis of different test techniques of DC circuit breaker

Abstract Amidst the escalating demand for energy and the proliferation of renewable energy sources, direct current (DC) systems have garnered increasing interest. As pivotal for the safety and reliability of DC systems, testing DC circuit breakers is a critical step to evaluate their performance and dependability. This study focuses on the breaking test method for medium and high-voltage DC circuit breakers. It compares and evaluates the current waveform, recovery voltage, and energy dissipation across various test circuit methodologies during the breaking process of DC circuit breakers and assesses the suitability of test methods across different voltage levels.

Overview of topology research on hybrid direct current circuit breakers

Overview of topology research on hybrid direct current circuit breakers

Experimental investigation on magnetically controlled air arc oscillation characteristics for DC interruption

With the development of the direct current (DC) power grid, the research of the forced current zero techniques in DC circuit breakers is of vital importance. Through applying an external alternating transverse magnetic field to an air arc confined by insulating walls, the arc can oscillate in a specific pattern, which is defined as ‘magnetically controlled arc oscillation’ in this article. The air arc oscillation characteristics are investigated through arc voltage spectrum analysis and arc motion captured by a high-speed camera. It can be found that the arc motion can be divided into a gliding process and a stretching process. The arc voltage oscillates at a particular frequency, which is nearly twice the magnetic field frequency. The basic arc oscillation pattern can be described from the aspects of arc voltage, arc column length and arc root velocity. Furthermore, this article proposes a DC breaking scheme based on the investigated magnetically controlled air arc oscillation characteristics. The forced current zero crossing point can be created in the resonant process between the oscillated air arc and the parallel-connected inductance-capacitance (LC) commutation path. Based on the proposed DC breaking scheme, interruption experiments are carried out, and it is observed that a current of 4.2 kA can be interrupted within several milliseconds. The feasibility of DC interruption based on magnetically controlled arc oscillation has been proved.

A Novel Direct Current Circuit Breaker with a Gradually Increasing Counter-Current

A reliable and cost-effective mechanical direct current circuit breaker (DCCB) is a promising solution for DC interruption. However, the typical mechanical DCCB has difficulty in interrupting a rated current, because the high oscillating current superimposed on the rated current generates a steep current slope at current zero-crossing (CZC) points, which makes it difficult for the vacuum interrupter to extinguish the arc. The objective of this paper is to present a novel DCCB topology with a gradually increasing counter-current. It utilizes a full-controlled converter, a semi-controlled full bridge, and an LC oscillation branch to generate a gradually increasing counter-current, which is superimposed on any fault current and generates a smooth current slope at CZC points. The proposed DCCB topology is modeled with PSCAD, and the current slope and the initial transient interruption voltage (ITIV) at CZC are analyzed and compared with the typical mechanical DCCB. The results indicate that the current slope at CZC decreases by 57–84% in full-range current interruptions, and the ITIV can be reduced by the same extent. Additionally, the performance of the proposed DCCB is evaluated in a four-terminal HVDC system. A cost and performance comparison is conducted among the main topologies. The obtained results show that the proposed DCCB is a reliable solution for the multi-terminal HVDC system.

Study of Energy Flow Mechanisms in High Power Device Converters

The work in this paper is applied to the Zhangbei Power grid. In the flexible direct current (DC) power system, the fault current rises extremely fast when a DC fault occurs. The requirements for the peak of breaking current and fault energy absorption of DC circuit breakers (DCCBs) increase linearly, which significantly increases the cost of the equipment. Therefore, in order to reduce the design difficulty of DCCBs, this paper proposes a strategy to control energy after the fault occurs. Firstly, the energy dimension is added on the basis of the traditional vector control of MMC, which constitutes a three-dimensional energy direct control. Subsequently, the architectures of energy fluctuation control and feedforward control are proposed. The influencing mechanisms for the peak fault current, peak fault voltage and energy dissipation are analyzed. Finally, the simulation of energy fluctuation control and feedforward control is constructed on PSCAD/EMTDC. The simulation results show that the energy fluctuation control is obviously better than the conventional three-dimensional energy control, and the feedforward energy control is further improved on this basis. Compared with the conventional vector control, the peak energy is reduced by 45.43% and the peak current is reduced by 25.39%, which helps to simplify the equipment design and reduce the equipment cost.

Design considerations of series type hybrid circuit breaker (S‐HCB)

AbstractThe series‐type direct current (DC) hybrid circuit breaker (S‐HCB) concept was previously reported to offer better performance than solid‐state circuit breakers (SSCB) and hybrid circuit breakers (HCB). S‐HCB offers low conduction power loss like an HCB and ‐scale interruption time, which is even faster than an SSCB. It uses a pulse transformer to isolate the lower‐voltage high‐inductance power electronic circuit from the high‐voltage, low‐inductance main power loop. This paper provides analysis of the impact of the S‐HCB circuit components on the overall system performance and a scalable S‐HCB design guide for different DC system voltage and current ratings. In addition, system energy flow analysis is performed in the time domain to provide an understanding of how energy is delivered, dissipated, and released throughout the entire fault interruption process. The S‐HCB prototype was experimentally tested at 3 kV/30 A and 6 kV/150A with the results showing the interruption of the low fault current of 30 A and the high fault current of 150 A within 8 and maintaining the fault current at a near zero value for 300 to enable an arcless opening of a series mechanical switch. The key design challenges of S‐HCB at high voltage and high current ratings were discussed and possible solutions to mitigate those challenges were introduced.

Study on the influence of mechanism dispersion on transient recovery voltage distribution of modular DC vacuum circuit breakers

AbstractA simulation analysis and an experiment are carried out to investigate how the gap difference between the breaks of a direct current vacuum circuit breakers with multi‐breaks (MB‐DC VCB) caused by the mechanism dispersion of the breaker influences the distribution of TRV among the breaks. An interruption model of MB‐DC VCB, combining the continuous transition model, is established to analyse the rising rate of transient recovery voltage and the dielectric strength recovery speed of the breaks for MB‐DC VCB under different gap difference conditions. Based on the experimental platform of dual break DC vacuum circuit breaker breaking, the correctness of the simulation model is verified on a DC VCB with the double‐breaks interruption experimental platform. Moreover, a model is applied to the non‐synchronous interruption simulation of a DC VCB with three‐breaks. The relationship between the TRVs of the breaks under different gap difference conditions is analysed using the comparative analysis method, obtaining the maximum gap difference at the moment of breaking failure. The results of this study show that large‐gap breaks have a higher TRV than small‐gap breaks (the fracture of the action delay module), with double fractures reaching 1.4 times and triple fractures reaching a maximum of 1.52 times; the ability of small‐gap breaks to withstand TRV is weak, giving rise to re‐breakdown or even interruption failure; as the number of fractures increases, the maximum gap difference also increases. Improving the synchronous interruption ability of the MB‐DC VCB is conducive to improving the interruption performance and interruption success rate of this type of a circuit breaker.

The energy dissipation topology and characteristics of GaInSn liquid metal and ZnO resistors based on high-voltage DC circuit breakers

High voltage direct current (HVDC) circuit breakers play a very crucial role in HVDC transmission systems. Energy dissipation circuit branches are the main part of the HVDC breaker. The volume and size of energy dissipation branches are the bottlenecks of the HVDC breaker, and the existing energy dissipation schemes can not meet the lightweight requirements. In this work, a combined energy dissipation scheme based on gallium indium tin (GaInSn) liquid metal and ZnO resistors is proposed for the energy dissipation branch of a circuit breaker. Firstly, the self-shrinking of GaInSn liquid metal mechanism is analyzed and the energy dissipation characteristics at different stages are investigated. The variation patterns of short circuit current, arc voltage, resistance and other parameters in the process of liquid metal arcing and energy dissipation are obtained. Secondly, the circuit model of liquid metal in arcing and energy dissipation process is established. The equivalent nonlinear time-varying conductance of the arcing process of the liquid metal dissipative element is simulated by combining the volt-ampere characteristic curves of the liquid metal dissipative module. Finally, the topology of energy dissipation circuit branches combined by GaInSn liquid metal and ZnO resistors is proposed. At the same time, the HVDC breaker model combined by a hybrid DC circuit breaker and energy dissipation circuit branches is constructed. The energy dissipation ratio and distribution law of GaInSn liquid metal and ZnO resistors in the composite type of circuit breaker are verified. The composite dissipation improves the overall energy dissipation density of the circuit breaker compared to the conventional ZnO resistors energy dissipation.

Study on impact of gap difference on plasma distribution of direct current vacuum circuit breaker with double-break

During the fault current breaking process of a mechanical direct current vacuum circuit breaker (DC VCB) with double-break (DB), the mechanism’s dispersion can result in a gap difference between the two breaks. A DB DC VCB breaking experiment platform is constructed in order to investigate the impact of gap difference on plasma distribution during the DB DC VCB breaking process. During the experiment, a high-speed camera is used to capture the vacuum arcing process at the two breaks under varying gap difference conditions. Then, the arc feature parameters and their variations during the zero-zone process are extracted using image processing techniques, and the distribution patterns of plasma and arc energy at the two breaks are analyzed and compared. When there is no gap difference between the two breaks of the experimental DB DC VCB, there are no significant differences in arc energy and the sizes of high-, medium-, and low-temperature plasma zones between the two breaks. When there is a gap difference between two breaks, the break with the smaller gap has larger high and medium-temperature plasma zones, more concentrated arc energy, higher particle concentration, lower arc diffusion velocity and arc energy decay velocity, and a greater amount of residual plasma after the extinguishing of the arc. When the gap difference exceeds a certain threshold, energy spots appear on the contact surfaces, and a high concentration corridor of residual particles remains between the contacts after the current crosses zero, forming a breakdown weak point that eventually leads to arc re-ignition (hence interruption failure) under the action of transient recovery voltage.

Robust Traveling Wave-Based Protection Scheme for Multiterminal DC Grids

The DC transmission line protection technology is crucial for the development of multi-terminal Voltage Source Converter (VSC)-based HVDC systems. This article proposes a robust non-unit traveling wave protection (TWP), which deals with the DC fault area identification and fault type discrimination for high impedance fault conditions. The authors applied the traveling wave (TW) reflection and refraction method for the line-mode network. The distinctive features of high-frequency components contained in the line-mode and pole-mode voltage TWs at different relay units are used for the algorithm modeling. Discrete Wavelet Transform (DWT) is selected as the time-frequency analysis tool. The performed simulations are conducted for a four-terminal VSC-HVDC system, and validate the protection feasibility and robustness. More precisely, the proposed protection scheme identifies the internal and external DC faults within 2 ms, and provides correct operation during high-impedance faults (HIF) with a 25 dB level noise interference. This protection scheme makes use of a VSC-assisted resonant current (VARC) direct current circuit breaker (DCCB), that successfully interrupts the fault currents in less than 10 ms after the fault inception. The authors also comprehensively compared the proposed scheme with the existing methods. The obtained results show that the proposed protection scheme is superior in terms of sensitivity and selectivity performance.

Cathode sheath parameters and their influences on arc root behavior after liquid metal bridge rupture in atmospheric air

The cathode sheath (CS) formation of the direct current air circuit breaker is simulated by a fluid model, and the influence of metal vapor concentration between the contacts after liquid metal bridge rupture is considered. The CS conductivity increases with the increasing concentration of copper vapor. The copper vapor concentration increases from 5% to 95%, and the thickness of the positive space charge layer and ionization layer increases from 22.3 and 49.1 μm to 51.8 and 81.7 μm, respectively. Increasing the CS conductivity is beneficial for the motion of arc roots in a certain range.

Analysis on DC Fault Current Limiting Operation of Twice-Quench Trigger Type SFCL Using Transformer Considering Magnetizing Current and Current Limiting Reactor

As the penetration of distributed energy resources (DER) has increased, research on direct current (DC) power transmission and distribution has been actively performed. The DC system has the advantage of high-power transmission efficiency. However, it has a very large and rapid increase in fault current in the DC system directly after a fault occurs. As one of the countermeasures, studies on the application of the superconducting fault current limiter (SFCL) into the DC system have been conducted to protect major facilities from DC fault current, which is expected to alleviate the power burden on the DC circuit breaker through its quench operation. Among the studied DC SFCLs, the trigger-type DC SFCL using a transformer, which can achieve the peak DC fault current-limiting operation, has been suggested. However, the DC fault current-limiting operation, in the case of the DC SFCL with a current-limiting reactor (CLR), was analyzed to not be effectively executed in the steady state since the transient state directly follows the fault occurrence. In this paper, the DC fault current-limiting operation of a twice-quench trigger type SFCL using a transformer considering magnetizing current and its CLR was analyzed. Through DC fault current-limiting experiments according to the inductance of its current-limiting reactor (CLR), the effective current-limiting design of twice-quench trigger type SFCL using a transformer was described.

An Efficient Bidirectional DC Circuit Breaker Capable of Regenerative Current Breaking for DC Microgrid Application

The direct current circuit breaker (DCCB) is extensively employed in DC microgrid applications to protect the network during faults. However, numerous DC converters are combined in parallel to form a DC microgrid, which creates a large network inductance. The grid stores energy during regular operation, which repels instantaneous current breaking, and this stored energy needs to be eliminated after current breaking. Conventional topologies use different energy absorption methods to dissipate the stored energy after breaking the current. In this paper, an efficient bidirectional DC circuit breaker (EBDCCB) topology is introduced to extract and reuse this energy instead of dissipating it. The proposed topology has bidirectional power flow capability to meet the requirements of DC microgrid applications as energy storage devices are frequently utilized. Furthermore, EBDCCB shows drastically improved performance in terms of current breaking time, voltage stress, regenerated average current, and energy recovery efficiency compared to the conventional DCCB topology. The mathematical modeling and sizing of the components used in the proposed EBDCCB are elaborately analyzed, and detailed performance testing is presented along with extensive PSIM software simulation. Additionally, an experimental investigation is conducted on a laboratory-scale 48 V/1 A prototype.

Zero-sequence current suppression control for fault current damper based on model predictive control

In a multi-terminal direct current (MTdc) system based on a modular multilevel converter (MMC), high-speed and large interruption capability direct current circuit breakers (dc CBs) are required for dc fault interruption. However, commercializing these breakers is challenging, especially offshore, due to the large footprint of the surge arrester. Hence, a supplementary control is required to limit the rate of current rise along with the fault current limiter. Furthermore, the operation of the dc CB is not frequent. Thus, it can lead to delays in fault interruption. This study proposes the indirect model predictive control (MPC)-based zero-sequence current control. This control provides dc fault current suppression by continuously controlling the zero-sequence current component using circulating current suppression control (CCSC) and by providing feedback to the outer voltage loop and inner current loop of MMCs. The proposed control is simulated for pole-to-pole and pole-to-ground faults at the critical fault location of an MTdc system. The simulation is performed in Real Time Digital Simulator (RTDS) environment, which shows that the predictive control reduces the rate of rise of the fault current, providing an additional 3 ms after the dc fault occurrence to the dc CB to clear the fault. Besides, the energy absorbed by the dc CB’s surge arrester during the pole-to-pole and pole-to-ground fault remains the same with the proposed control.

Research on circuit breaker failure protection and the secondary accelerated fault isolation scheme of VSC-HVDC grids

When the direct current circuit breaker (DCCB) fails to operate, the fault range will further expand, endangering the safe operation of the power gird. Therefore, this study proposes a DCCB failure protection method and a secondary accelerated fault isolation scheme of voltage source converter-based high-voltage direct current (VSC-HVDC) grids. On the basis of considering the influence of DCCB disconnection, characteristics of fault current after the failure of the DCCB are analyzed, and a circuit breaker failure protection method based on “increase current” discrimination is proposed. By analyzing the logical relationship among failed breaker re-tripping, adjacent DCCB action, blocking of the converter station, and AC circuit breaker action, a secondary accelerated fault isolation scheme is proposed to minimize the fault isolation area. The scheme achieves the accelerated isolation of DC faults after the failure of the DCCB and avoids the trip of the AC circuit breaker effectively. Simulation results verify the effectiveness of the proposed scheme.

Novel Active Snubbers for SSCBs to Improve Switch Voltage Utilization Rate

This paper proposes two novel active snubbers for direct current (dc) solid-state circuit breakers (SSCBs): metal-oxide-varistor with resistor-capacitor-switch (MOV-RCS) and active-MOV with resistor-capacitor-diode (AMOV-RCD). In the snubber branch, either half- or full-controlled switch can be applicable, leading to four novel topologies. There are two main contributions: 1) MOV is disconnected from the power line during SSCB OFF-state, which enhances reliability as neither voltage nor power appears on MOV; 2) voltage utilization rate η <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><i>v</i></sub> of the main switch is remarkably increased, which improves efficiency and power density, and reduces design cost. Experiments of five prototypes are conducted including four proposed snubbers and a comparison with conventional MOV-RCD snubber. Results show that, for 1.2 kV MOSFETs as the main switch, new snubbers can enhance η <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><i>v</i></sub> from 37.5% to 60%, achieving 183 A dc current interruption under 720 V dc bus voltage within 2.4 μs. Meanwhile, the voltage peak is limited to 1.112 kV.