Superconducting Fault Current Limiter Research Articles

Current limiting and recovery characteristics of an AC fast recovery superconducting fault current-limiting breaker

With the continuous development of the power grid, the high short-circuit fault current threatens the reliability of the power system. When the short-circuit current is greater than the interrupting capacity of the circuit breaker, the fault current will not be interrupted. Resistive-type superconducting fault current limiter (R-SFCL) has little loss in normal conditions. When a short-circuit fault occurs, R-SFCL can respond within a few milliseconds and limit the fault current. But the recovery time of R-SFCL is too long to satisfy the reclosing demand in the power grid. In this paper, an AC fast recovery superconducting fault current-limiting breaker (FR-SFCB) is proposed. With the operation of a fast switch connected with the superconducting coil, one of the parallel superconducting branches is disconnected, which could provide higher current limiting resistance and decrease the fault current need to be interrupted in fault conditions. Because of the shorter current flowing time, the heat generation and temperature of the advanced disconnected branch are less which can reduce the recovery time significantly. An experimental model is established based on thyristors and superconducting tapes. The effects of prospective current (I p) and the types of superconducting tapes on the current limiting resistance and recovery time of FR-SFCB are investigated. Experimental results show that with the disconnection of the flowing branch, the current limiting resistance of the proposed FR-SFCB increases to more than 3 times of the normal R-SFCL. At the same time, when the FR-SFCB resistance after current limiting is lower than the room temperature resistance, the recovery time of the flowing branch decreases by at least 50%. With access to fast switches, the proposed FR-SFCB can suppress the short-circuit fault current effectively and improve the stability of the power system.

Development of a DC hybrid fault-current limiting and interrupting device for microgrid applications with a new approach for current-limiting capability

This research presents the development of a hybrid DC fault current limiter (HDCFCL) for microgrid applications. The proposed HDCFCL configuration comprises two parallel branches; the first is the main circuit, which includes a superconducting material as a current limiting element in series with the auxiliary solid-state switch. The second branch includes the commutation circuit, composed of two groups of ultra-fast turn-off semiconductor switches, IGCTs, connected back-to-back across the absorbing energy branch. A new approach to the current limitation is presented, where a superconducting fault current limiter is used to reduce the short circuit current together with a capacitor to absorb the energy of the commutation circuit during the interrupting process. The PLECS program was used to analyze the results theoretically, and they were verified via building and testing a laboratory prototype. The experimental results showed the capability of the proposed system isolating the fault within 3.6 ms, which is quite fast compared to other presented systems in the relevant literature.

A novel configuration approach of SFCLs in the power grid and its economic analysis

The superconducting fault current limiter (SFCL) is expected to be a good choice for cooperating the circuit breakers to cut off large fault current. In order to achieve better economic benefits and meet the current limiting requirements of the power grid, a novel configuration approach of SFCL is proposed. The sensitivity factor is utilized to select the type of SFCL and the candidate transmission branches for SFCL to be installed. The particle swarm optimization with shrinkage factor (XARPSO) and the Pareto principle is introduced for determining optimal configuration of SFCLs. Then, the net present value (NPV) index method is proposed to conduct the economic analysis of an SFCL, considering the total device cost and the whole network power loss. Besides, the economic comparison between SFCLs and conventional current-limiting air core reactors (ACR) is carried out. Finally, the IEEE 39-bus system is built and a large amount of calculation results show that the SFCL have promising application prospects in limiting the fault current and reducing the network loss.

Optimal placement of resistive superconducting fault current limiter by considering short‐circuit current and transient stability of power system

AbstractHigh level of fault currents has become one of the most challenging issues, along with increased electrical energy consumption and power grid expansion. However, some of the previous work was limited to installing limiters on designs and installing them on small plans. Here, the optimal placement of a resistive‐type superconducting fault current limiter (RSFCL) to achieve good power system transient stability is proposed. The proposed method has several advantages. First, procedure fault analysis is applied to consider the magnitude of the short‐circuit currents and the line located close to the generator for the placement of the device. Compared with other methods, it can directly find the exact line to be installed RSFCL. Second, the stability assessment is validated using the time domain simulation by installing limiters with varying capacities in any location. Third, parameters were analysed to evaluate the proposed method's effectiveness, including angular speed, rotor angular velocity, and generator rotor angle in a multi‐machine system. The result reveals that the placement of the limiter on the line with the most significant short‐circuits value on the line closest to the generator increases the power system stability more than the placement in other locations.

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.

Analysis on Protection Coordination of OCRs Using Index for Impedance Compensation Considering Unsymmetrical Ground Fault in a Power Distribution System With SFCL

The superconducting fault current limiter (SFCL) has been spotlighted as the effective device to limit the fault current because it has no effect on a power distribution system in a normal time due to its zero resistance. However, the SFCL causes the trip of the overcurrent relays (OCRs) to be delayed due to the reduc-tion of the fault current, which causes a negative impact on the protection coordination of power distribution system. The delayed trip of OCR makes the exposure time's increase of the neighboring power facilities from the fault current at fault line. In this paper, the OCR's index for the impedance compensation of the SFCL in case of the unsymmetrical ground fault was suggested. The sug-gested OCR's index consists of all sequence components for the impedance, calculated from the voltages and the currents meas-ured from both the power distribution system and the SFCL. To prove the effectiveness of algorithm, the protection coordination between OCRs in a power distribution system with the SFCL were analyzed for the unsymmetrical ground fault as well as the sym-metrical ground fault through the simulation using PSCAD/ EMTDC.

A Study on Increasing the Capacity of Transformer-Type Superconducting DC Circuit Breaker

Superconducting Fault Current Limiter (SFCL) can increasethefaultcurrent-limitingratethroughtheseriesconnection of superconducting elements, and through this, it can be applied to systems with high capacity. However, when multiple superconduct-ing elements are connected in series, unbalanced quench character-istics may occur continuously due to problems of critical character-istics andpartialquenching.Wehaveproposedaquenching method ofbalancedSFCLusingthe neutrallinetosolvethisproblem.Inthis paper, we applied several superconducting elements with the neu-trallinetoincreasethecurrent-limitingrateofthetransformer-type superconducting current limiter module (T-SFCL module). Inaddi-tion, when the T-SFCL module was combined with the DC circuit breaker, the operating characteristics of the superconducting DC circuit breaker were confirmed. As a result, power consumption of superconducting elements was balanced due tothe balanced quench of superconducting element, and fault current was reduced due to the highcurrentlimitingcharacteristics of superconducting element.

High Temperature Superconductivity Application Readiness Map - Energy Delivery - Transmission, Substation and Distribution

The International Energy Agency's High Temperature Superconductivity Technology Collaboration Program (IEA HTS TCP) analyzed energy delivery applications for HTS. The product was a Readiness Map that illustrates the Technology Readiness Levels (TRL) over time of HTS applications. Assessing these TRL levels is important since the electric power system that supplies our residential, commercial and industrial sectors is experiencing a transition to safer, more efficient and cleaner power supply. The international experts assessed the present degree of technological development of the main transmission, substation and distribution HTS applications in the energy delivery sector and estimated the pathway to commercialization phase. Instead of using a specific TRL number 1-9 for each of the applications, they are categorized into low, medium and high TRL levels. Superconducting fault current limiters and medium voltage AC cables to interconnect substations at the low side of the transformer are currently at a high TRL as they can be purchased in the market. High voltage AC and DC cables are at a medium TRL and could reach a high level TRL level in 2030-2035. Superconducting transformers are at a low TRL and they could reach a high TRL level by 2030-2035.

Protection System Architecture for All-Electric Aircraft

To reduce emissions from the aviation industry and meet the targets set by different countries, research has been focused on investigating all-electric aircraft. To make this vision practical, superconducting machines are expected to power the propellers, as they are half the size and a third the weight of conventional machines. The main purpose of this paper is to do a higher-level study of a reliable holistic protection system for all-electric aircraft; that can reduce heat leakage and be able to detect faults reliably. Thus, three main protection systems were investigated; 1) cryogenic voltage source converter superconducting magnetic energy storage system (VSC-SMES), 2) cryogenic dc breaker integrated with superconducting fault current limiter (SFCL), and 3) machine learning algorithm for fault detection. By immersing the protection system at cryogenic temperature, the paper has shown that passive leakage can be eliminated, and thus more energy can be saved for the fuel cell. The paper has also demonstrated that using machine learning for the SFCL-dc-breaker system can consistently eliminate faults and protect the system.

DC Fault Current Limiting Characteristics of Flux-Lock Type SFCL With Parallel Connection of Two Coils Using Twice Quench

In this paper, DC fault current limiting characteristics of DC flux-lock type superconducting fault current limiter (SFCL) with parallel connection between two coils were analyzed. DC flux-lock type SFCL with parallel connection between two coils was composed of two windings connected in parallel and two superconducting modules (SMs), which were connected in series with each secondary winding. DC flux-lock type SFCLs with a parallel connection between two coils and one SM with one secondary winding in series was thought to perform fault current limiting operation as in AC system. However, since the transient period after resistance generation in SM approaches into the constant value, unlike the AC system, there is a DC current limiting transient period. Therefore, the DC current limiting effect disappears in the DC system and the recovery characteristic after the fault is removed also disappears. To analyze the DC fault current limiting and recovery characteristics, a DC short-circuit test was per-formed, and the various behaviors of flux-lock type SFCLs in DC systems were investigated from the test results.

Applicability Analysis of a Multi-Filar Meander R-SFCL and an RSC-DCCB in an MMC-MTDC Grid

modular multilevel converters (MMC)-based high voltage direct current (HVDC) topology is an effective solution to solve the power transmission demand between countries. However, the initial fault current can rise to several tens of kA within a few ms by capacitor discharge during a fault. This fault current can permanently damage the converter components and cables. Therefore, to increase the stability of the system, the protection of the DC system is very important. DC system protection methods include circuit breaker technologies and current limiting technologies. We have selected a circuit breaker with combined resonant current source (RCS) and a resistive superconducting fault current limiter (SFCL) as protection methods for the DC system. The RSC-DC circuit breaker has no conduction power losses by on-state voltage drop. Therefore, it can provide stable interruption compared to a solid-state DC circuit breaker. Since the resistive SFCL has a very fast response time, it can effectively limit the rapidly rising initial fault current. We wound the superconducting tape by the multi-filar meander method. This method can increase the length of the superconducting tape used and speed up the bubble diffusion during quenching. We modeled an MMC-HVDC grid, resistive SFCL, and RCS DC circuit breaker using PSCAD/EMTDC. In this paper, the interrupting and current limiting characteristics are discussed when the resistive SFCL and the RCS-DC circuit breaker proposed by us are connected to the MMC-based MTDC grid. In the simulation, the current limiting factor of resistive SFCL was up to about 58%. In addition, the combination of resistive SFCL and RCS-DC circuit breaker can shorten the interruption time when the fault occurs.

Current Limiting Simulation of Magneto-biased Superconducting Fault Current Limiter (SFCL)Applied in 66 kV/10 kV Power Substation in China

The short-circuit fault currents in the large capacity transmission lines pose a challenge to the stability and safety of power system. Magneto-biased superconducting fault current limiter (MBSFCL) is with the advantages of two-stage current limiting, self-triggering and fast recovery so that it can effectively reduce the short-circuit fault current when applied to the urban power system. This paper analyzes the operation principle of MBSFCL and establishes a package type magneto-thermal coupled simulation model of MBSFCL based on MATLAB/SIMULINK. A power system model of a 66 kV/10 kV Zhang Tai Zi power substation which is in Liaoning province in China has been established and the grid-connected simulation applied MBSFCL has been achieved. Moreover, the grid-connected test is carried out, and the results of fault current, quench resistance and temperature change are obtained. The comparison of results between simulation and test verifies the accuracy of the simulation model and the application feasibility of MBSFCL.

Breakdown Phenomena in Liquid Nitrogen Under Synchronized Transient Boiling and Impulse Voltage

Resistive superconducting fault current limiters constitute a promising solution for high voltage networks. During the resistive current limitation, transient overvoltages and heat dissipation occur on superconducting tapes, inducing fast boiling of surrounding liquid nitrogen (LN <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> ). An experimental system reproducing the fast transient heating of a tape electrode, synchronized with a high voltage impulse is described. Breakdown voltages measurements in both polarities are carried out versus synchronization delay, pressure (0.10 to 0.40 MPa), temperature (77 K and 65 K). Breakdown voltages show complex variations with these parameters. More insight is obtained from the recording of pre-breakdown phenomena (streamer). The size of vapor bubbles has a large and counter-intuitive influence on streamer initiation: the smaller bubbles, the lower inception voltage. Subcooling LN <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> (by decreasing temperature and/or increasing pressure) sometimes has a beneficial influence (quenching of negative streamer propagation), but deleterious effects can be as well observed in other circumstances (by favouring positive streamer initiation).

Performance Analysis of Resistive Superconducting Fault Current Limiter Using LN2and GHe Cooling

Large-scale electric aircraft is a disruptive technology to address the environmental impact of air travel. Fault current limitation is crucial to realise the safety and reliability of the electric aircraft, in particular for large-scale electric aircraft using DC distribution network. This paper investigates the behavior of the resistive SFCL under different cryogenic cooling systems including liquid nitrogen and helium gas circulation cooling systems for the electric aircraft DC distribution network. Electromagnetic and thermoelectric models were used to predict the characteristics of resistive SFCL. The simulation results demonstrate that it is promising to design resistive SFCL using liquid nitrogen cooling as well as helium gas circulation cooling systems, which offer flexibility for SFCL cryogenic cooling system for electric aircraft applications.

Mechanism of Recovery Performance Improvement With Porous-Stabilized REBCO Tape for Resistive-Type Superconducting Fault Current Limiters

Resistive-type superconducting fault current limiters (R-SFCLs) utilizing rare-earth barium copper oxide (REBCO) tapes have been developed to limit fault currents. To balance recovery and current-limiting performances, a porous-stabilized REBCO tape was proposed. The experimental results showed that using a porous stabilizer with the REBCO tape and insulating epoxy reduced recovery time to 25%. However, the underlying mechanisms of this improvement in recovery performance are not yet clear. The aim of the present study is to understand these mechanisms. To do so, a vapor-film-collapse model was proposed to clarify the impact of the insulating epoxy on vapor film collapse. This model suggests that when liquid nitrogen (LN <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> ) comes into contact with the insulating epoxy, it causes a rapid decrease in the temperature of the insulating epoxy surface, leading to the collapse of the vapor film. Additionally, a liquid-retention model was proposed to investigate the effect of the porous stabilizer. This model indicates that if the porous stabilizer can retain LN <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> , the equivalent heat flux observed in experiments can be achieved through evaporation of the retained LN <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> .

New technique for improving transient stability of standalone microgrid using superconductor fault current limiter

This study proposes a new insertion topology for Superconductor Fault Current Limiter (SFCL) to maintain and enhance the transient stability of a wind generation system in a standalone microgrid. The proposed topology is inserting the SFCL in series with the faulty phase only. The new insertion topology performance is compared with the traditional insertion method. The proposed insertion topology of the SFCL displays excellent performance compared to the traditional method. The overall performance of the Micro-Grid is improved. The performance of the wind generator is improved dramatically after employing the proposed controller. The proposed insertion topology suppresses the fluctuations of the wind generator speed (from ± 6% to less than ± 1%) as well as the post fault wind generator real power and imaginary power. For a single line to ground fault, the wind generator active power fluctuates between + 80 kW, and − 40 kW with traditional SFCL insertion topology. When using the proposed insertion topology, the wind generator active power fluctuates between + 27 kW, and + 12 kW. Also, the proposed SFCL insertion topology mitigates the fluctuations in voltage, real power and imaginary power not only at the generator bus but also at all other Micro-Grid buses (PV bus, and storage batteries bus). The voltage at all buses recover to steady state values fast (0.01 s) compared with the recovering time when using the traditional method (nearly 1 s). The proposed method is very simple and low cost because there is no additional hardware is required. This fact makes the proposed method highly attractive from the economical and implementation point of views.

A robust single ended disturbance detection scheme for superconducting fault current limiter integrated UPFC compensated line

The occurrence of short circuit events in a high voltage or extra high voltage transmission system may result in a fault current with high magnitudes. Additionally, the inclusion of Unified Power Flow Control (UPFC) contributes to fault current. In such a scenario, the use of Superconducting Fault Current Limiters (SFCLs) is very vital because of their better technical performance to limit fault currents. However, inclusion of SFCL may cause difficulties for existing disturbance detection units. To overcome such an issue, this manuscript aims for a new disturbance detection approach based on sliding window Singular Spectrum Analysis (SSA). The proposed method begins with the reconstruction of the fault signal using SSA and then computes the transient error by subtracting the reconstructed fault signal from the original signal. This transient error is used as a fault detection index (FDI) which is also used to classify the faulty section. The superiority of the presented technique is tested for two different UPFC compensated power networks equipped with two different SFCLs, modeled using EMTDC/PSCAD 5.0. The obtained results show the effectiveness of the addressed method, obtained by simulating different adverse scenarios (fault and non-fault) which justify the real-time application of the proposed protection method.

Impact of superconducting fault current limiter with delayed recovery on transient rotor angle stability

A fault current limiter (FCL) is an economical option to limit the increased fault current levels, which may also improve the rotor angle stability. Previous studies on this topic mainly focused on the FCLs with quick recovery and concluded that the FCL improves the rotor angle stability. However, some commercially available FCLs have delayed recovery, which may pose different challenges and need to be studied. This paper studies the impact of a superconducting fault current limiter (SCFCL) with delayed recovery on transient rotor angle stability. This paper first develops an analytical understanding of the stability of a system with SCFCL using the equal area criterion. Later, time-domain simulations are employed to demonstrate the impacts of the SCFCL on the rotor angle stability of a single-machine infinite-bus system. The results show that the SCFCL with delayed recovery leads to rotor angle instability in some cases.

Research on damage characteristics and microscopic appearance of ReBCO tapes after DC overcurrent

With the expansion of the power grid, the use of DC transmission technology is becoming increasingly prevalent. This has led to higher transmission voltage levels, which in turn have brought to the fore the issue of large short-circuit currents. The existing circuit limiter’s performance is insufficient to meet the growing demand. Superconducting fault current limiter, which based on ReBCO tapes, is considered to be the solution to the problem of large short-circuit current. However, the failure mode of ReBCO tapes under DC overcurrent remains to be studied. In the superconducting state, the current flows mainly through the superconducting layer. Therefore, it is necessary to investigate the overcurrent characteristics of the superconducting layer after overcurrent. In this work, the damage characteristics and microscopic appearance of ReBCO tapes after overcurrent were investigated. The magnetic field distribution characteristics and the microscopic appearance of the superconducting layers of ReBCO tapes with different degrees of critical current recession were investigated, and the chemical elements of the superconducting layers were analyzed. The results show that large-area pits were found on superconducting layer after overcurrent, the element types and mass proportions did not change. Overcurrent affects the superconductivity of the tape mainly by changing the physical structure of the superconducting layer.

Design of a 110-kV 2.0-kA SmartCoil Superconducting Fault Current Limiter

The concept of a SmartCoil fault current limiter consists of a conventional primary winding at room temperature which induces a current in the secondary superconducting winding. This arrangement allows to retrofit an air core reactor with secondary, short-circuited high temperature superconducting tapes. This work investigates the designs of a 110 kV 2.0 kA SmartCoil fault current limiter, which reduces a prospective fault current of 13 kA to 4.5 kA. In the design process the geometric dimensions of the primary winding and the number of the superconducting rings in the secondary coil are varied. Key optimization criteria are to keep the stray reactance between 1% and 5% while the impedance during short circuit conditions must be in the range between 20% and 40%. An excessive heating of the superconductors must be avoided. Transient simulations are also carried out to verify all the performance requirements are fulfilled. Finally, a design proposal with 3 limiter modules in series with all parameters including heat input and cooling is presented. The design meets all requirements by the distribution system operator.