The Superconducting Fault Current Limiting Transformers (SFCLTs) offer significant advantages such as large capacity and high efficiency. However, a challenge arises in maintaining power transmission during some short-circuit fault conditions, as this may lead to the inability of superconducting tapes to recover from quenching, resulting in damage due to overheating. A variable impedance superconducting fault current limiting transformer (VI-SFCLT) was designed as two parallel superconducting branches in a secondary winding to recover seamlessly with the system load after fault current limitation. In this manuscript, an experimental platform is constructed to test the current limiting and recovery performance of the VI-SFCLT under load current after a fault. The experimental results demonstrate that the proposed VI-SFCLT can limit the fault current to 40% lower than the normal SFCLT. The joule heat of the VI-SFCLT can be 78.3% of the normal SFCLT with the increase of fault duration, and the recovery time is at least 26.2% shorter. By incorporating a fast switch, VI-SFCLT achieves rapid recovery with load current, thereby enhancing the stability of the power grid.

The objective of this study is to investigate the barrier effect on dynamic breakdown characteristics in liquid nitrogen (LN2) under transient bubble disturbance for resistive-type superconducting fault current limiters (R-SFCLs). An R-SFCL model with superconducting coils (SCs) immersed in LN2 is tested under static and dynamic conditions, with and without an insulation barrier for both dc polarities. Breakdown voltage and time delay T-d are measured across varying energy densities (0.29, 0.49, and 0.62 J/cm). The results show that the insulation barrier enhances the breakdown voltage of the R-SFCL model in the quenching state. The presence of the insulation barrier reduces T-d to a certain value when the energy density of the superconducting tapes exceeds a critical threshold, achieving a minimum delay of 7 ms. Polarity effects reveal superior insulation strength under negative polarity than that of the positive one in the R-SFCL model. These findings provide critical insights for optimizing R-SFCL insulation design and guiding dc circuit breakers (DCCBs) interruption timing, ensuring reliable fault current management in high-voltage dc (HVdc) systems.

Liquid nitrogen has demonstrated promising DC interruption capability under cryogenic conditions, which may facilitate the realization of cryogenic hybrid DC circuit breaker. During interruptions, the liquid nitrogen gap must withstand the transient recovery voltage to prevent arc restrikes. However, existing studies mainly focus on gaseous media and vacuum. Dielectric strength recovery of liquid-nitrogen gaps remains absent. This paper aims to characterize the dielectric strength recovery behavior of liquid nitrogen gaps under different arc currents, arc duration and transverse magnetic fields. The results show that after the free burning arc extinguished, the dielectric strength of the liquid nitrogen gap follows a logarithmic regression function. Under a transverse magnetic field, the dielectric strength exhibits a two-stage logarithmic growth. The transverse magnetic field significantly enhances the dielectric strength recovery level of the liquid nitrogen gap. A 50 mT transverse magnetic field increases the withstand voltage by an average of 60% at 20 ms after arc extinction. However, the recovery rate and final dielectric strength level of the electrode gap do not increase with increasing magnetic field strength. The findings of this paper may provide support for insulation design of a hybrid DC circuit breakers employing liquid nitrogen as the arc-quenching medium, contributing to the feasibility of fault-protection strategies for superconducting DC electric-propulsion systems.

With the continuous expansion of power systems, the addition of transmission lines, and the increasing interconnection and meshing of power grids, short-circuit fault currents have continued to increase. The resistive-type superconducting fault current limiters (R-SFCLs) can significantly reduce the short-circuit current interrupted by circuit breakers, thereby reducing the electrical, thermal, and mechanical stresses on the breakers and improving their interruption margin, operational reliability, and service life. During the quenching and recovery processes of R-SFCLs, the heat generated by the superconducting coils causes the surrounding liquid nitrogen to boil and generate bubbles, which influence the heat transfer. However, relatively few studies have examined the influence of the moving bubbles on the quenching and recovery characteristics of superconducting coils. The objective of this paper is to obtain the influence of bubbles on the superconducting coil's quenching and recovery characteristics. Based on this, to design and develop a 12 kV/630 A R-SFCL. Experiments were conducted to observe the generation and movement of the bubbles during quenching and recovery. Electromagnetic-thermal-fluid simulation models for non-inductive pancake coils that account for the influence of moving bubbles were established. A comparison of simulation and experimental results of current-limiting and recovery for pancake coils shows the errors below 9.4% for the current peak and 11.2% for the recovery time to 77 K. The electromagnetic-thermal-fluid model improves the accuracy of recovery time to 92 K predictions for the prototype superconducting coils by up to 69 ms at specific locations compared to the electromagnetic-thermal models ignoring bubble effects. Then a 12 kV/630 A R-SFCL prototype was designed and fabricated based on the results. Experimental and simulation results demonstrate that under fault current of 35 kA, the prototype achieves a first peak current-limiting ratio of 88.6% and a maximum unit-length quenching resistance of 0.06 Ω/m, much lower than its room-temperature resistance of 0.1 Ω/m, confirming its capability to withstand fault current of 35 kA.

Quartz sand current-limiting fuses are widely used in power systems. Successful fault interruption critically depends on the fuse’s ability to withstand transient recovery voltage (TRV) without dielectric breakdown during the post-arc stage. This paper experimentally investigates the influence of fuse element materials (copper, silver, copper-silver composite material) on the post-arc dielectric recovery of quartz sand fuses. Results demonstrate that fuses with copper elements exhibit superior dielectric recovery, achieving a dielectric strength of 336.57 V within 30 μs in post-arc stage, which is 1.74 and 2.71 times higher than copper-silver composite (193.15 V) and silver (123.85 V) elements, respectively. Mechanistic studies reveal that copper enhances dielectric strength through synergistic effects of high ionization energy (suppressing arc gas ionization) and high electron work function (reducing electrode electron emission). This study establishes that fuse element materials regulate post-arc dielectric recovery through dual mechanisms (electrode properties and arc composition), providing critical insights for high-performance fuse design.

Resistive type Superconducting fault current limiter (R-SFCL) can be combined with DC circuit breaker (DCCB), which can suppress the DC fault current and decrease the interrupting requirement. However, the resonant capacitor of the forced zero crossing DC circuit breaker (DCCB) need to be pre-charged with a higher voltage, which reduces the opening reliability. In this paper, the resonant capacitor of DCCB is charged by the quenching voltage of R-SFCL (self-charging SFCB), so as to realize adaptive charging of different short-circuit currents. The resonant capacitor charging characteristics by the quenching voltage of R-SFCL is analyzed through simulation, and the simulation results is verified by experiments. Subsequently, the superconducting current limiter self-charging interrupting experiments is carried out. The experimental results show that the superconducting current limiting can limit the 20 times critical current (Ic) by 60.2

High-current interruptions aggravate arc contact ablation, and arcing time strongly influences the gas-blast capability of self-energy SF6 circuit breakers. This study quantifies the effect of arcing time on gas flow characteristics while accounting for cumulative arc contact ablation over repeated operations. A T100a test is performed on a 40.5 kV/31.5 kA self-energy SF6 circuit breaker, and an enthalpy-flow model is established and validated against measurements. Numerical analyses are then conducted for 1-11 interruption operations. The pressure in the expansion chamber at the current zero crossing (P-cz) increases first and then decreases with increasing arcing time, and longer arcing times lead to a larger P-cz drop after repeated operations. After 11 operations, P-cz decreases by 52.14% at 22.5 ms (tau = 75 ms) and by 60.33% at 23.9 ms (tau = 120 ms). The P-cz drop percentage exhibits a quadratic dependence on arc energy, with fitted coefficients increasing with operation count. Overall, an arcing time window of 9.6-20 ms provides the best compromise between interruption margin and cumulative degradation in this study.

High temperature superconductor (HTS) can be used to limit and interrupt fault current as a fuse. However, the narrow neck on the side of the tape causes lower and unstable critical current, which makes its application difficult. In this paper, we proposed a new type of superconducting fuse with a narrow neck manufactured in a stainless-steel (SUS) reinforcement layer, which can hold the critical current and enhance the fusing ability. An experimental model was established with an impact source. The AC current limiting and fusing tests were conducted with the new superconducting fuse and the fuse without a narrow neck. Experimental results show that compared to the fuse without a narrow neck, the new superconducting fuse achieves a reduction of at least 40 A in peak current, an increase of at least 77.4% in arc voltage, a decrease of at least 17% in front arc I^2t, and a shorting of at least 0.872 ms in pre-arcing time. The superior current-limiting and fusing capabilities of the new superconducting fuse can help protect superconducting devices during fault conditions.

High voltage SF6 circuit breakers are critical for the safety and stability of power systems. The key to research their interruption performance is focused on arc modeling and experimental data processing. Traditional black-box arc models exhibit shortcomings in parameter searching. To address it, this paper proposes an arc model parameter search method based on T100a test from a 363 kV high-voltage sulfur hexafluoride (SF6) circuit breaker, leveraging the advantages of the parameter-reduced TP KEMA model in arc modeling. An enhanced particle swarm optimization(PSO) algorithm is employed: first using variable-step search to approach optimal points, then applying the PSO algorithm for parameter fitting. The fourth-order classical Runge-Kutta method is applied to construct the difference form of the TP KEMA arc model, thereby completing the arc model construction. Simulation verification shows an average arc voltage error of 65.34 V. Among five test datasets, only one simulation interruption result differed from the experimental result, achieving an 80

Superconducting DC power distribution systems, pivotal next-generation technology for decarbonizing aircraft transportation, face significant fault isolation challenges. Liquid nitrogen, serving as coolant and insulator for high-temperature superconducting devices, demonstrated substantial arc-quenching capability. It may offer potential for robust fault-clearing solutions in superconducting networks. However, arcing in liquid nitrogen constitutes a complex multiphase phenomenon, involving simultaneous vapor-liquid-plasma coexistence. Fundamental understanding of both arc characteristics and their underlying combustion physics in liquid nitrogen remains limited. This study identifies key factors governing arc behavior in liquid nitrogen. A dedicated experimental platform acquiring synchronized electrical signals, high-speed imaging, and fluid pressure data was developed. A coupled gas–liquid evolution model was established to simulate associated fluid dynamics. Results demonstrated near-synchronization between arc voltage rise and pressure transients. Dynamic pressure changes and vapor layer development drive distinct arc voltage phases. Crucially, arc energy dominated phase-transition dynamics, while resultant vapor-liquid distribution modulated arc power dissipation through thermo-fluid interactions. This interdependence established a closed-loop coupling mechanism governing arc transient behavior.

Presently, air type DC circuit breakers are extensively deployed in rail transit DC traction systems. During interruption processes, these devices must dissipate substantial energy stored in system inductors, resulting in prolonged breaking times of several tens of milliseconds. This leads to severe contact erosion and necessitates substantial volumes for arc blowing. As the power capacity of DC traction systems increases, the performance requirements for DC circuit breakers become more stringent. To address these limitations in conventional air DC breakers, this paper proposes a Composite switching apparatus. The integrated device effectively combines fuses with forced current-zero vacuum interruption technology. The forced current-zero vacuum switches interrupt rated operating currents and overcurrents up to $\mathbf{2 0 k A}$, while DC fuses interrupt prospective short-circuit currents of 100 kA. Experimental results demonstratde successful interruption of 20 kA overcurrent by vacuum switches and prospective 100 kA short-circuit current by fuses, with respective breaking times of 5.12 ms and 5.09 ms. Through optimized design of fuse pre-arcing characteristics, precise coordination between the two interruption technologies was achieved, significantly enhancing overall breaking capacity. This approach may effectively reduce both the magnitude and duration of short-circuit current stress on online power equipment.

With the continuous development of power grid, the high short-circuit threatens the stability of the power system. The short-circuit exceeds the disconnection capacity of the circuit breaker and has a negative impact on the integrity and stability of the power grid. Therefore, the research and application of the fault current limiter (FCL) has become particularly important, especially the superconducting fault current limiter (SFCL), which uses the zero resistance characteristics in the superconducting state and shows obvious advantages in the power system. In this paper, the current limiting and recovery performance of a variable resistance SFCL (VR-SFCL) is investigated. A test model is built with a 2 kV/20 kA LC source. The effects of the shunt branch parameters on the current-limiting resistance and recovery time are investigated. And further analysis of a 10 kV/630 A system is made through simulation based on the experimental results. From the test and simulation results, the parallel branch parameters can be designed from the current limiting demand, and the minimum tape length can be calculated from the fitted equation with recovery in 300 ms, which can be used to design VR-SFCL with appropriate tape length.

With the advancement of renewable energy sources such as photovoltaic plants and wind farms, the capacity of the DC grid is increasing rapidly. Larger grid capacity results in higher requirements of current load and interruption capacity in the DC circuit breaker (DCCB). However, the capacity of a single vacuum switch is limited to load several kiloampere system currents. Parallel vacuum switches are needed to achieve higher load capacity. In this paper, to analyze the current transfer in parallel vacuum switches, a DC short-circuit simulation model is established with DCCB consisting of two parallel vacuum switches. The short-circuit current transfer between parallel vacuum switches and interruption characteristics of DCCB with different fault currents and tripping time intervals are investigated. From the experimental results, with the same tripping time interval, higher short-circuit current results in longer current transfer time. With larger tripping time intervals, the longer time current transferring will be used. The paper provides the maximum tripping time interval when the current cannot be completely transferred. It shows that in a DC system with a high load current, parallel vacuum switches can be used in DCCB with short tripping time intervals.

High-voltage circuit breakers play an importance role in power systems, yet they face significant challenges under complex breaking conditions. This paper investigates the influence of pressure chamber volume on the asymmetric short-circuit current breaking performance of SF6 self-powered circuit breakers. A physical model of the arc enthalpy flow is established, and simulations are conducted using HVCB software based on the actual structure of a 40.5 kV circuit breaker. Parameters such as asymmetric short-circuit current, arcing time, and structural characteristics of the circuit breaker chamber are considered. The simulation results indicate that, under rated breaking current and maximum asymmetry conditions, increasing the pressure chamber volume leads to a reduction in both arc voltage peak and expansion pressure. Consequently, for a circuit breaker with a pressure chamber volume ranging between 0.0008 m3 and 0.0014 m3, a smaller volume enhances its asymmetric breaking performance.

With the development of power grids, the interrupting performance of high-voltage self-extinguishing SF6circuit breaker faces challenges. This paper conducts theoretical analysis of the enthalpy flow physical model and valve motion equations of the circuit breaker, supplemented by HVCB software simulations. The results indicate that the circuit breaker can successfully interrupt the current under medium and short arcing time conditions when the expansion chamber pressure reaches 1.370 MPa and the mass flow rate between the chamber and arc exceeds 2.126 kg/s. When the interface area between the compression chamber and expansion chamber varies from 100 mm2 to 2500 mm2, the pressure and mass flow rate in the expansion chamber first increase and then decrease. When the connecting area between the cooling chamber and adjacent chambers varies from 9000 mm2 to 16000 mm2, the pressure and mass flow rate in the expansion chamber remain essentially stable. This study reveals the intrinsic correlation between interface area and interrupting performance, providing theoretical guidance for the optimized design of high-voltage self-extinguishing SF6circuit breakers.

This paper proposes a voltage-clamped AC fault current limiter (VCA-FCL) based on coupled inductance to address the challenges of excessive short-circuit current (SCC) and transient components in power systems. VCA-FCL integrates reverse coupled inductors, metal oxide varistors (MOVs), and IGBTs, achieving near-zero impedance during normal operation and fast current limiting during faults. The clamping voltage function of MOV suppresses the peak value of SCC, reduces the influence of transient components, and accelerates the zero crossing of current. The simulation in the 220 kV system showed that the peak value of SCC decreased by 85.2% (from 18.54 kA to 2.75 kA). Compared with traditional fault current limiters, it provides a more efficient solution. The results verified the feasibility of improving the stability of the power grid and the performance of circuit breakers.

The high-speed grounding switch is an important component of gas-insulated switchgear (GIS), which is used to quickly cut off the fault current. However, it is difficult to break the Class-B electromagnetic induction current when the environmental-friendly high-speed grounding switch is working in the high-voltage condition. In this article, a method of rotating the gas arc by magnetic blowing is proposed to change the arc morphology through the action of electromagnetic force, in order to drive the arc to rotate and come into full contact with the air. This method is expected to cool the arc temperature rapidly, increase the instantaneous power dissipation, and enhance the arc quenching capability of high-voltage equipment. This article through the establishment of gas arc magnetohydrodynamics (MHD) simulation model analyzes the gas arcing characteristics in the magnetic field, and finally uses a high-voltage power supply to the test switchgear to complete the arcing experiments. The results show that after adding the magnetic field, the highest air arcing peak power is 5.96 times higher than that without the magnetic field, which verifies the effectiveness of this method in improving the performance of small-current disconnecting.

With the continuous increase in grid capacity and the rise in the time constant of the DC component of short-circuit currents in power systems, the hidden dangers of insufficient interrupting capability of circuit breakers have become increasingly prominent. Therefore, it is crucial to study the factors affecting the interruption performance of circuit breakers. The article establishes a physical arc simulation model based on the internal structure of high-voltage SF 6 circuit breakers, and investigates the effects of the time constant of the DC component of short-circuit currents, arcing time, and initial pressure of the puffer chamber on the interruption performance of the circuit breakers. The results show that increasing the arcing time and initial pressure of the puffer chamber facilitates circuit breaker interruption, while an increase in the DC component tends to lead to interruption failure. These findings provide a theoretical basis for improving the capability of high-voltage circuit breakers to interrupt asymmetric short-circuit currents.

Turbo-Electric Distributed Propulsion Aircraft (TeDP) is an advanced aircraft concept for the future that utilizes a DC power distribution system to address the challenges of power transmission and distribution. One of the major obstacles hindering the development of this technology is the issue of isolation and interruption in cases of DC faults. The method of limiting current using superconducting fault current limiters (SFCL) and interrupting with a DC circuit breaker (DCCB) has received significant attention. The primary aim of this paper is to examine the coordination between various types of SFCL and DCCB. On one hand, this study conducts simulations and analysis on the response of saturated, resistive, and hybrid SFCLs to fault currents. The results demonstrate that all three SFCL types exhibit a current limiting effect of 40% and can effectively work in conjunction with DCCBs to successfully eliminate faults. However, when compared to the other two types, R-SFCL demonstrates greater flexibility and is capable of significantly reducing voltage and current stress on the DCCB.

With the background of difficulties in breaking Class B electromagnetic induction current for the 252 kV environment-friendly Gas Insulated Switchgear(GIS) products, to enhance the ability of breaking low current, establish the gas arc numerical calculation model, and simulate the arc external characteristics and physical parameters, as a judgment of low current breaking capacity. In combination with the arc numerical calculation model, we analyze the efficiency of cooling the arc through magnetic blowing, then assisting the arc quenching and optimizing the low current breaking performance of high-voltage equipment. Finally, the LC discharge circuit is used to supply power for the test switchgear, and the arcing experiment under a high-voltage environment is designed and completed to analyze the relevant factors affecting the gas arcing process and to optimize the arc numerical calculation model. During the experiment, we found that the arc-burning time can be shortened from 200 ms to about 120 ms, which means the method worked.