Hypergeometric behavior of metal oxide varistors in DC circuit breakers

Introduction. The article investigates the problem of interrupting large inductive currents during short-circuit faults in direct-current traction networks of urban electric transport and metro systems. High load dynamics, increased short-circuit levels and the absence of a natural current zero crossing significantly complicate the extinction of a direct-current electric arc. Traditional circuit breakers often demonstrate insufficient speed or excessive contact wear, which creates the need for forced arc-extinguishing schemes. Goal. The goal of this work is to experimentally investigate the performance of a direct-current circuit breaker equipped with a forced arc-extinguishing scheme under short-circuit conditions defined by IEC 61992-2, namely: the maximum current amplitude mode (f), the maximum energy mode (e), the distant short-circuit mode (d). Methodology. The paper describes the operating principle of the breaker employing an LC-commutation circuit that generates a counter-current for arc extinction in the vacuum interrupter. Experimental tests were carried out at the IPH Institute laboratory (Berlin). For each test mode, supply parameters, oscillograms are presented. Results. The breaker successfully passed a series of tests, ensuring reliable interruption of short-circuit currents in all three modes. The key experimental parameters are: in mode f: peak current 71,8 kA, total break time 1,94 ms, overvoltage 1,95 kV; in mode e: sustained short-circuit current 42,2 kA, total break time 4 ms, overvoltage 1,77 kV; in mode d: sustained short-circuit current 8,14 kA, total break time 3,9 ms, overvoltage 1,47 kV. Practical value. The test results confirm the reliable operation of the LC-commutation scheme and stable current zero crossing in the vacuum interrupter. The studied breaker can be practically implemented at traction substations of urban electric transport and metro systems as a faster and more reliable switching device.

Characteristics evaluation of reverse blocking diode thyristor for DC circuit breaker

Topology design of current injection DC circuit breaker based on coupling reactor

Abstract Microstructure homogeneity and grain size reduction are needed to ensure the current uniformity and reliability required in metal oxide varistors for DC circuit breakers. Cold sintering (CS)–a low‐temperature digestive liquid and high‐pressure densification process–has previously shown reduced grain growth, but it is not clear how the lower processing temperatures will impact the bismuth intergranular phases that induce current nonlinearity. This study investigates the impact of CS on the microstructure and nonlinearity of bismuth added to ZnO varistors. ZnO powders with 0–1 mol% Bi 2 O 3 are either CS at 300°C and 300 MPa or high temperature sintered (HTS) at 1100°C. CS samples reach >97% of the theoretical density. The 1 mol% Bi 2 O 3 CS samples have limited grain growth with a final average grain size of 120 ± 85 nm, while the HTS sample shows over 1.991% increase to a grain size of 2.99 ± 1.17 µm. No Bi‐rich intergranular phase is observed in the CS samples, but bismuth clearly increases resistivity with increasing bismuth concentration, with a higher voltage onset for nonlinearity and an increase in nonlinearity with increasing bismuth. This work demonstrates the ability to use cold sintering to create dense ZnO ceramics with reduced grain growth and controlled nonlinearity.

ABSTRACT Driven by the global “dual carbon” goals, the development of new clean energy technologies has brought opportunities for DC power equipment, and the pyrolysis mechanism of gassing materials in DC circuit breakers needs to be clarified. This study takes three high‐performance polyamide materials (PA46, PA66, and PA6) as the research objects, uses ReaxFF reactive force field molecular dynamics to simulate their pyrolysis processes and compares them, and validates the results with macroscopic material analysis techniques. The simulation analyzes the decomposition pathways of materials under arc discharge, the formation mechanisms of small‐molecule products, etc., revealing different bond‐breaking mechanisms. In terms of carbon residues, PA66 has the fewest three‐membered rings, while PA46 has the highest total carbon ring content. On the other hand, macroscopic experiments on carbon deposition and partial discharge indicate that, among the three gassing materials, PA66 exhibits relatively better insulation performance, PA46 shows the highest sensitivity to partial discharge, and PA6 falls in an intermediate position. This performance ranking is consistent with the amount of tar and coke generated in simulations. Qualitative and quantitative analyses of carbon ring formation and experimental results further verify the feasibility of studying microscopic mechanisms via simulations. The study provides a reliable method for screening gassing materials and offers insights for the innovative development of power equipment.

The influence of stray inductance in DC circuit breakers on IGCT devices

An adaptive current commutation for hybrid DC circuit breaker

ABSTRACTIn solidly grounded bipolar high‐voltage direct current (HVDC) grids, DC faults can cause rapid current surges due to inherent pole‐to‐pole coupling, posing significant risks to system stability. Traditional traveling‐wave protection methods, though unaffected by MMC control characteristics, face challenges in bipolar systems where coupling complicates fault identification and necessitates costly DC circuit breakers (DCCBs). To address these limitations, this paper proposes a hybrid modular multilevel converter (MMC) topology based on an improved dual half‐bridge submodule (IDHSM) with self‐clearing capability and a coordinated control‐protection (CCP) strategy. The proposed method enables dynamic adjustment of activated submodule ratios through an adaptive modulation coefficient, achieving a 14.93% reduction in DC voltage under a 300‐Ω fault resistance while maintaining arm current constraints. Compared with full‐bridge submodules (FBSM), this hybrid topology reduces IGBT counts per voltage level by 50%, lowering hardware costs. Simulation results on a four‐terminal HVDC grid demonstrate that the proposed strategy enables DC fault identification within 1 ms using modulus instantaneous average values, effectively addressing the sensitivity degradation caused by MMC‐based current limiting. Moreover, the DCCB breaking current is reduced by 30% (from 7.0 to 4.9 kA) through coordinated current limiting. The proposed strategy exhibits strong performance across a wide transition resistance range of 0.1–300 Ω. Moreover, a low‐voltage experimental platform is built to verify the effectiveness of the proposed protection strategy.

A novel thyristor-based hybrid DC circuit breaker with the ability to identify the type and location of the fault before reclosing the MMC-HVDC grid

A novel thyristor-based DC circuit breaker with integrated current limiting reactors

A fault location method for DC distribution networks with DC circuit breaker and current limiter coordination

A Novel Lifespan Approach for Assessment and Selection of Damping Systems Used in Hybrid DC Circuit Breakers Employed in Railways

Designing multi-terminal HVDC systems presents significant challenges, particularly in control, modeling, and protection. One of the most critical concerns is the protection of these systems from DC short circuits. DC circuit breakers (DCCBs) have traditionally been a key solution for handling fault conditions. However, as these systems scale up to meet increasing power demands, the associated cost and technical complexity of deploying DCCBs across large-scale systems make them less practical and economically viable. This has driven the exploration of alternative or supplementary strategies to address short circuits more cost-effectively. In this regard, fault current limiter (FCL) circuits combined with DC breakers have been proposed to reduce their demands. This paper presents an improved non-superconducting FCL circuit paired with a hybrid DC circuit breaker to enhance system performance. The proposed topology integrates power electronic (PE) bidirectional switches, current-limiting inductors, and a discharging resistor. Simulations have been conducted using PSCAD/EMTDC software. An equivalent circuit model based on the Zhoushan HVDC project is used for simulation analysis to study behavior under the influence of this breaker. In contrast to current approaches that utilize continuous current-limiting components, the proposed topology minimizes power loss during normal operation. The simulation results show robust current-limiting performance, quicker fault isolation, and reduced energy absorption by the breaker. With the proposed circuit, the fault clearing time is improved by 23%, and energy absorption performance is enhanced by 98%. Compared to the existing topology in the literature the proposed design demonstrates superior current limiting performance. The proposed FCL reduces the fault current to 2 kA whereas the literature reported topology limits it to 2.5 kA. Further, it achieves significantly lower energy absorption, measured at 0.12 MJ compared to 0.4 MJ in the literature. A comparative analysis with the existing methods from the literature demonstrates that the proposed FCL offers superior current-limiting capabilities, faster fault response, and lower power losses.

Abstract Abstract—High voltage DC circuit breakers require rapid dissipation of megajoules of energy during the breaking process. The use of gallium-indium-tin (GaInSn) liquid metal can quickly dissipate energy, but traditional single hole liquid metal energy dissipation devices have disadvantages such as low energy consumption efficiency, short service life, and high manufacturing costs. This paper proposes and designs liquid metal arc chamber structures with series connected double holes and series connected three holes to address the many shortcomings of single hole structures, and builds experimental and simulation platforms for liquid metal arc. Research has found that in terms of energy consumption efficiency, as the number of series connected holes increases, the energy consumption efficiency of liquid metal arc chambers is significantly improved, especially under high current amplitudes, where the energy consumption efficiency of porous structures is much higher than that of single pore structures. In terms of rapid response capability, the pre arc contraction time of porous structures is shorter than that of single pore structures, exhibiting faster response speed. In addition, porous structures have significant advantages in terms of service life and manufacturing cost in slowing down baffle erosion and reducing mechanical stress inside the combustion arc chamber.

Multi-parameter optimization and design of self-triggered low voltage hybrid DC circuit breaker based on machine learning

Improving the Practicality of Innovative DC Circuit Breakers Using Linear Motors

Abstract Power electronics switching devices played an important role in high-voltage DC circuit breaker development. Timely isolation of faulty portions of an HVDC transmission line from a healthy system is a basic requirement for a fault interruption. In this scenario, the integration of hybrid DC circuit breakers (HDCCBs) with wideband-gap semiconductor devices enables the effective management of high power, currents, and voltages. The SiC-MESFET and the GaN-HEMT are commonly used wideband-gap-based semiconductor devices. This paper introduces a fault interruption scheme for HVDC power systems, featuring the advancement of a hybrid DC circuit breaker. The proposed HDCCB design consists of two parts, one part is based on a VCB as a mechanical circuit breaker, and the second part involves electronic switches for fault interruption. The electronic switches are designed through the combination of GaN and HEMT to achieve fast switching to achieve rapid interruption of fault current. The system model is implemented through a Simulink model to perform a comparative analysis between the presented and existing protection topologies. Current commutation is achieved through the attainment of artificial zero current crossing to interrupt the DC fault. GaN-HEMT emerges as a more reliable and fast switching element compared to other electronic switches like Sic-MESFET as validated by the presented simulative results. The presented model shows better fault-clearing times of 2.2 ms and 2 ms for experimental parameters of (500 kV and 9kA) and (100 kV and 10kA), respectively. This fault-clearing time shows an improvement of 52.38% and 50% compared to the SiC-MESFET-based electronic switches used by the existing mechanisms. The outcomes of the proposed design are evaluated in terms of fault current, commutated current, and voltage across the commutated capacitor.

Abstract Low voltage direct current (LVDC) distribution network is one of the important carriers of new DC sources and loads. However, the voltage source converter (VSC), as its important energy conversion device, does not have fault ride-through capability. At the same time, traditional DC circuit breakers are difficult to isolate faults before VSC is blocked, which makes LVDC system have huge potential safety hazards. This paper proposes a fault adaptive current limiter (FACL) for LVDC systems to address these issues, offering superior current limiting performance to traditional schemes. At the same time, FACL has a certain voltage clamping ability, so VSC has a certain fault ride-through capability. First, the paper introduces the topology and working principle of the proposed FACL. This topology can ensure “low intervention” during normal operation and “effective current limiting” during faults. Subsequently, the parameter design scheme of FACL is proposed. Additionally, the proposed scheme is verified by simulation. Finally, the conclusion of this study is given.

Investigation of the Electromagnetic Force and Contact Spring in Rotational Ultrafast Disconnector in Railway DC Circuit Breaker