High Voltage DC Circuit Breaker Research Articles

Study on the Design of Valve Base Insulation and Power Supply Transformer for High-Voltage DC Circuit Breaker

Abstract High-voltage DC circuit breaker is a key piece of equipment to building DC power grids. DC circuit breakers need to support and isolate from high voltage to ground through valve-based equipment and use valve-based power supply transformer to continuously supply energy to high potential components, the electrical performance of these two equipment determines whether DC circuit breakers and DC networks can be operated safely and reliably. For this reason, this paper carries out the research on the insulation capability of the valve base and the performance of the power supply transformer, such as the design and simulation of electric and thermal fields, as well as the test program. Firstly, the insulation design and simulation study of the valve base as a whole is carried out, and the design optimization of the equipotential scheme of the top homogeneous tubular bus, diagonal pull insulator and hydroelectric pole is completed. Secondly, the design and simulation verification of the thermal field distribution of the energy-supply transformer, the overvoltage between the ends of the output windings and the optimization scheme, and the short-circuit impedance were carried out. Finally, the insulation performance of the valve base, the temperature rise of the energy supply transformer, the overvoltage simulation of the output winding and the short-circuit characteristics were tested. The results show that: after optimization, the maximum field strength of the homogenizer is 2.3kV/mm, and the overall maximum field strength of the valve base is 2.61 kV/mm on the diagonal insulator, and there is no pressure difference between the water circuit and the fittings using the three-pin vertically distributed hydropower electrode scheme; the temperature rise of the supply transformer in the simulation and the actual measurement is 27K and less than 30K; by means of the parallel connection of the MOV, the overvoltage of the output winding of the power supply transformer under voltage impulse is effectively reduced to -1.8kV; the measured short-circuit impedance of the power supply transformer is 69.5%. The optimized design of DC circuit breaker valve base and power supply transformer can operate safely, and effectively support the construction of DC circuit breaker and DC power network.

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.

A novel multi-port hybrid high voltage DC circuit breaker commutated by controllable active oscillation circuit

The hybrid high voltage DC circuit breaker (HDCB) is widely regarded as the most promising solution to the fault current interruption of VSC-based DC grids. However, because of a large number of power electronic modules connected in series in transfer branch, the cost of existing HDCBs are pretty high, which limiting their large-scale commercial application. In this paper, a novel multi-port hybrid high voltage DC circuit breaker commutated by controllable active oscillation circuit (CAOC-MPHDCB) is proposed. Based on the principle of controllable active oscillation, the proposed CAOC-MPHDCB can realize the reliable commutation and fast interruption of fault current while significantly reducing the total cost and operation loss. In addition, the CAOC-MPHDCB can not only isolate line faults that occur continuously in a short time, but also maintain system ring-network structure after isolating the faulty DC bus. The influencing mechanism of parameters on the performance of CAOC-MPHDCB are analysed in detail, and the selection methods of corresponding parameters are obtained. The simulation results show that the principle of CAOC-MPHDCB is effective and feasible.

Glass-Fiber-Reinforced 3D h-BN Skeleton for Epoxy Resin Insulation: Increased Arc-Ablation Resistance and Mechanical Strength

Epoxy resin (EP) as an insulation material is widely used in aerospace, transportation, long-distance power transmission, and other fields requiring large electrical equipment. However, the concurrent arc-ablation resistance and mechanical strength of EP have long been a bottleneck for building electrical equipment and electronic devices suitable for extreme environments, whereas existing modification technologies generally fall well short of the requirement for practical engineering applications. Herein, authors use fully exfoliated hexagonal boron nitride (h-BN) nanosheet (BNNS) and epoxy-group-grafted glass fiber (eGF) as reinforcement material to construct a 3D eGF-BNNS ordered framework via an ice-crystal-induced orientation control process. The EP/3D eGF-BNNS composite, which serves as a thermally conductive framework, is prepared by vacuum-assisted impregnation. This approach considerably enhances the ability of EP to manage large thermal loads and endows the skeleton with stronger tearing strength and tighter interfacial adhesion with the EP matrix; thus, the thermal conductivity of the EP insulation is enhanced by a factor of 19.2, the arc-ablation resistance by a factor of 3.46, and the tensile strength by 85.5%. The improvement of these properties is of great significance for optimizing the insulation of high-voltage dc circuit breaker.

Design and Study of the Key Characteristics of a New DC Vacuum Interrupter With a High Peak and Low Residual Magnetic Field

With the rapid development of multiterminal high-voltage direct current (HVdc) transmission systems, the research and development of high-speed and stable high-voltage dc circuit breakers have received attention. Among them, mechanical dc circuit breakers based on manual zero-crossing dc breaking technology have been applied in practical projects, owing to their small size, low on-state loss, and low price. However, this method adds a high-frequency current, which deteriorates the magnetic field between the poles of the interrupter when the arc is broken. Therefore, the development of HVdc circuit breakers that maintain high peak magnetic fields and low residual magnetic fields at high frequencies has become the key to the development of multiterminal HVdc transmission. To solve this problem, this article proposes a new interrupter for a vacuum dc circuit breaker based on artificial zero-crossing technology and studies its key characteristics, such as temperature rise, electromagnetic field, and arc column plasma distribution characteristics. The results reveal that the new interrupter proposed in this article has a low-temperature rise, uniformly distributed electric field, high peak value and low remanence of the longitudinal magnetic field, and uniformly distributed plasma in the arc column, and exhibits arc diffusion. Its ability to cope with high-frequency current is significantly higher than that of the traditional cup-shaped axial magnetic field (AMF) contact system interrupter, which is conducive to the high-speed and stable breaking of the interrupter.

The Application of Vacuum Interrupters in HVDC Circuit Breakers

It has become necessary to develop high-voltage dc (HVDC) circuit breakers to protect against fault currents that may occur in HVDC grids. One possible HVDC circuit breaker design uses vacuum interrupters as the main dc current path and the dc current interrupter using a counter-pulse system to create an artificial current zero. As the counter-pulse has a relatively high– di / dt, the vacuum arc mode at the current zero is critical when withstanding the resulting transient interruption voltages (TIVs). The fault current in the dc system can also increase rapidly to a very high value. In order to prevent serious damage to the dc grid, it is imperative that the vacuum interrupter open soon after the fault is detected and the counter pulse applied in order to limit its magnitude. This article discusses the vacuum arc modes as the contacts open and the requirements to create a fully developed diffuse vacuum arc at the counter-pulse current zero. The vacuum interrupter also has to develop a large enough contact gap in order to withstand the expected recovery voltages (TIVs). To do this a high-speed opening mechanism is required. Thus, the vacuum interrupter will accelerate faster than it would have experienced in a high-voltage ac (HVAC) vacuum circuit breaker. The article presents the critical design parameters for the vacuum interrupter to operate in a HVDC vacuum circuit breaker and contrast them with vacuum interrupters used in HVAC circuit breakers.

Current Limiting Hybrid High Voltage DC Circuit Breaker With Reclosing Function Limiting

Current Limiting Hybrid High Voltage DC Circuit Breaker With Reclosing Function Limiting

Thermal FEM Analysis of Surge Arresters During HVdc Current Interruption Validated by Experiments

This paper deals with the development of an accurate finite-element model of an arrester to investigate the electrothermal and mechanical stress during dc current interruption. The comprehensive analysis performed on a ZnO surge arrester is supported by experiments during high-voltage dc circuit breaker current interruption. The performed experimental analysis comprises three sequential 26 kV/10 kA direct current interruption tests carried out within a period of one hour. The dynamic temperature and current distribution of the surge arrester columns during current interruption are measured. The finite-element simulation results are in good agreement with the test results. The influence of the surge arrester temperature on the current distribution among the surge arrester columns is analyzed. The impact of the surge arrester temperature on ZnO electrical characteristics and mechanical stress inside the surge arrester are also investigated. The surge arrester finite-element model can be used with full success for parameter optimization of the surge arresters to prevent possible failures when dc circuit breakers performed multiple interruptions in short period of time.

Parameters design of voltage sharing components for the series multi‐break mechanical switch

Series multi-break mechanical switch is one of the critical components of high-voltage hybrid DC circuit breakers. However, due to the existence of distributed capacitance, the voltage distribution between the breaks is not balanced. This paper proposed a voltage sharing configuration method of the mechanical switch of hybrid DC circuit breaker, and carried out the static DC voltage and the transient voltage distribution characteristics tests to verify its effectiveness. Considering the influence of whole structure of the circuit breaker, this paper established the electrostatic field model and circuit simulation model of a typical ±535-kV hybrid DC circuit breaker. And it analyzed the influence of single break's opening fault, breaking open distance, and the shielding fitting on the voltage distribution characteristics of series six break mechanical switch. According to the simulation results based on the Zhangbei voltage source converter-based high-voltage direct current project type test parameters, the parameters design of the voltage sharing components of the mechanical switch are obtained, which can meet the voltage sharing coefficient requirement of 95%.

A Contribution to the Development of High-Voltage dc Circuit Breaker Technologies: A Review of New Considerations

To promote the integration of renewable energy resources into modern energy systems, high-voltage dc (HVdc) and circuit breaker (CB) technologies have become critical to achieving secure and efficient energy transmission. This article reviews the technical development of the related areas, compares diverse breaker concepts and topologies, investigates possible coordination and testing solutions, and points out the remaining challenges as well as future needs. The time-domain simulation and comparative analysis are adopted in this article to analyze and compare the performances of different HVdc CBs. By making use of different selectivity levels of multiterminal HVdc (MTdc) grids, the suitable planning and placement of HVdc CBs can be conducted. Furthermore, by providing insights into the performance of HVdc CBs, the work presented in this article can serve as a useful asset for the upcoming standardization and industrial application process of HVdc grid and CB design and testing.

New Topology of Multi-port High-Voltage DC Circuit Breaker with Current-Limiting Function

New Topology of Multi-port High-Voltage DC Circuit Breaker with Current-Limiting Function

Hybrid HVDC circuit breakers with an energy absorption branch of a parallel arrester structure

Hybrid circuit breakers (CBs) are the most promising technology to isolate DC faults in modular multilevel converter (MMC)-based DC grids. However, they consist of expensive power electronic components that are sensitive to high overvoltage and overcurrent. This study proposes a hybrid high-voltage DC circuit breaker with an energy absorption branch of a parallel arrester structure, and investigates the possibility of reducing the fault current and the switching overvoltage. First, the basic principle of an energy absorption branch with a parallel arrester structure is presented. Then, the simultaneous and sequential insertion strategies are illustrated. Second, each strategy and each structure are combined separately to analyse their respective characteristics in reducing the overvoltage, the fault current, the energy absorption and the fault clearance time. The sequential insertion strategy of the proposed energy absorption branch is proved to have the best performance. Finally, the trade-offs between these four metrics are achieved through the non-dominated sorting genetic algorithm II (NSGA-II). A general method to determine the parameters of the proposed energy absorption branch from the Pareto front based on different preferences is provided. Simulations on PSCAD show that sequential insertion of the proposed energy absorption branch with the optimal parameters is able to suppress the switching overvoltage and limit the fault current to a relatively low extent simultaneously.

Low Inductance Design for Symmetrical Submodules in Hybrid HVDC Circuit Breaker

The diode bridge submodule (SM) is one of the basic units of a hybrid high-voltage dc circuit breaker. This article works on the low inductance design of a single SM and series SMs. For the layout design of a single SM, this article proposes a simple and clear +-shaped SM layout, the low inductance design is simplified to the optimization of two laminated busbars with a simple structure. Based on the +-shaped SM layout, this article further proposes an SM structure with holes in diodes region, the stray inductance is further reduced, and only one integrated laminated busbar is needed in a single SM. For the layout design of series SMs, this article makes full use of the layout of a single SM and the mutual inductances between the SMs, series SMs are alternately connected in reverse. The single SM layout proposed in this article is effective in reducing the stray inductance. The loop stray inductance in stage II reduced from 148.4 to 72.3 nH, a 51.3% reduction. When the two parallel IGBTs turn off a 6 kA fault current in 2 μs, the voltage spike is reduced from 786.1 to 423.4 V, a 46.1% reduction. And the stray inductance difference of the bidirectional current path is controlled to about 10 nH. The layout of series SMs proposed in this article is effective in reducing the length of the series SMs, the length is reduced by 16.7%. The experimental results show that the SMs layout proposed in this article is effective.

Modularization design methodology for high-voltage mechanical DC circuit breaker with current commutation drive circuit

With rated voltage of multi-terminal direct current (MTDC) power transmission system varying from ±160 kV to ±500 kV and even ±800 kV, high-voltage direct current circuit breaker (DCCB) is in urgent demand. With remarkable features of low operating losses, free-maintenance, and relative small investment, DCCBs based on mechanical vacuum switch (MVS) and current commutation drive circuit (CCDC) are recognized to have bright prospects in practical engineering. However, parameters design and serial topology selection for high-voltage mechanical DCCB with CCDC are still open problems. Motived by this, parameter design method for a modularized DCCB with CCDC is proposed. Then, parameters of 500 kV DCCBs with two typical serial topologies, namely, modularized serial topology and integrated serial topology, are optimized, and simulations are conducted in PSCAD/EMTDC for verification. In the end, performances of the two serial topologies, including dynamic voltage balancing, fault-tolerance capability and cost, are discussed. According to research results, modularized design methodology is recommended for high-voltage DCCB with CCDC.

Technical Assessment on Self-Charging Mechanical HVDC Circuit Breaker

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.

Time-Varying Resistance Optimization for the Resistive Type Superconducting Fault Current Limiter Applied in VSC-HVDC System

When short-circuit fault occurs in a voltage source converter–based high-voltage direct current (VSC-HVDC) transmission system, the fault current curve is much more complex than conventional AC power grid. The high-voltage DC circuit breaker with large cut-off capacity is rather expensive; thus, some current limiting methods are proposed to limit the fault current. The superconducting fault current limiter (SFCL) is one of the promising devices for both AC and DC short-circuit current limiting application. The optimization criterion for SFCL applied in VSC-HVDC system is presented, and a four terminal VSC-HVDC system is adopted as an example. The short-circuit fault could be divided into condenser discharge and AC system feeding process, and the fault current curve is related to the time-varying RLC parameters of the grid. The thermal and resistance characteristics of the SFCL are analyzed, and the optimization method of the current limiting impedance and thermal characteristics of the SFCL is developed based on the time-varying fault current. Finally, the design of a 160-kV SFCL was completed based on the proposed method.

Control strategy of transfer branch for reducing peak value of DCCB breaking current

A high-voltage DC circuit breaker is one of the key equipment that constructs the DC power grid. Therefore, reducing the peak value of the breaking current and shortening the fault removal time are the main research directions for its performance optimization. This paper first analyzes the basic topology and the traditional breaking strategy of a hybrid high-voltage DC circuit breaker with forced current commutation. Then, the theoretical analysis of the fault current, voltage, and the relationship between the withstand voltage level of the fast mechanical switch and the exit time of the transfer branch, is conducted. A new breaking strategy is proposed, which can effectively reduce the peak value of the breaking current by turning off the transfer branch step by step. When a fast mechanical switch reaches the corresponding withstand voltage level, it sends the OFF signals to each sub-module of the transfer branch; thus, the energy consumption of the DC circuit breaker is reduced and the fault removal time is shortened. Finally, the PSCAD/EMTDC simulation platform is used to build the test system, which verified the effectiveness of current limiting and other functions of the proposed breaking control strategy.

A State-of-the-Art 500-kV Hybrid Circuit Breaker for a dc Grid: The World's Largest Capacity High-Voltage dc Circuit Breaker

High-voltage dc (HVdc) circuit breakers (CBs) are a key technology of multiterminal dc (MTdc) systems and grids. In this article, a state-of-the-art 500-kV hybrid CB (HCB) topology is proposed and compared with other existing HCB solutions. Implementing the topology includes three important components: a modular designed high-current bidirectional solid-state switch (SS), an ultrafast mechanical switch (MS) based on a Thomson (CCDC) equipment with no conduction loss, whose corresponding functional verification test results have been presented in detail. On this basis, the overall 500-kV HCB and a comprehensive experimental platform are developed. Detailed experiments, including 25-kA turn-off and reclosing experiments, are conducted. The HCB was found to be capable of breaking a 25-kA current in 2.7 ms with 800-kV overvoltage, which is on par with the level of leading CBs worldwide.

Electric Contact Material Selection for Medium and High Voltage DC Circuit Breakers

Medium and high voltage DC grids are increasingly proposed for terrestrial, shipboard and aircraft power systems. However, multi terminal DC networks can only be realized with the development of a DC circuit breaker. Due to the difficulty in breaking DC currents, hybrid circuit breakers—which consist of a non-arcing fast mechanical disconnect switch (FMS) in parallel with a solid state switch—is the most promising solution. The stresses experienced by the electric contacts of FMS are different from those of AC and low voltage DC breakers and disconnect switches. The choice of contact material has a significant impact on the performance of the DC circuit breaker. The Ashby method is used to systematically identify the best suited contact materials by translating the requirements of FMS contacts into objectives and constraints and deriving material indices for each objective. Minimizing power loss, wear and overheating of contacts are identified as the key objectives. The results suggest that copper-based alloys and compounds are more suitable than silver based alloys and compounds and other contact materials.

HVDC Circuit Breakers–A Review

HVDC circuit breakers are of increasing importance, as multi-terminal high voltage DC (HVDC) transmission becomes a commercial reality. Multiple HVDC breaker technologies have been developed, and are starting to appear as proof-of-concept installations on real networks. Information about them is however distributed widely in the literature. This article describes the underlying challenges, the leading candidate solutions, and discusses the requirements and construction of the component sub-assemblies. Its goal is to provide a comprehensive overview of the field.