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Abstract: The recloser that is used in distribution systems is a relay system that behaves sequentially to protect power systems from transient and continuous faults. This reclosing operation of the recloser can improve the reliability and stability of the power supply. For cooperation with this recloser, the superconducting fault current limiter (SFCL) must properly perform the reclosing operation. This paper analyzed the reclosing operation characteristics of the three-phase flux-coupling type SFCL in the event of a ground fault. The fault current limiting characteristics according to the changing number of turns of the primary and secondary coils were examined. As the number of turns of the first coil increased, the first maximum fault current decreased. Furthermore, the voltage of the quenched superconducting element also decreased. This means that the power burden of the superconducting element decreases based on the increasing number of turns of the primary coil. The fault current limiting characteristic of the SFCL according to the reclosing time limited the fault current within a 0.5cycles (8ms), which is shorter than the closing time of the recloser. In other words, the superconducting element returned to the superconducting state before the second fault and normally performed the fault current limiting operation. If the SFCL did not recover before the recloser reclosing time, the normal current that was flowing in the transmission line after the recovery of the SFCL from the fault would have been limited and would have caused losses. Therefore, the fast recovery time of a SFCL is critical to its cooperation with the protection system. [Copyright &y& Elsevier]

Abstract: When the fault occurred in the power system, the superconducting fault current limiter (SFCL) rapidly limited the fault current to protect the power devices with preventing power failure. Therefore, the application of the matrix-type SFCL in the power system could improve of its reliability and stability. To apply the SFCL into the real power system, many superconducting elements should be connected in series and parallel. If any superconducting element of the matrix-type SFCL breaks down, it cannot basically limit the fault current. In this paper, we analyzed operation stability of the matrix-type SFCL which was divided into trigger and current-limiting parts as follows: Case 1. Break-down of a superconducting element in the trigger part. Case 2. Break-down of a superconducting element in the current-limiting part. Case 3. Break-down of two superconducting elements in the current-limiting part. When any superconducting element was broken down, we confirmed that all fault current flowed into other normal superconducting element connected in parallel and its power burden was largely increased. At that time, the matrix-type SFCL was operated well to limit the fault, but the fault current was decreased a little bit because the resistance generated in the superconducting element was abruptly increased. If the excessive current of the superconducting element exceeds its capacity, it could cause the break-down of the other superconducting element, shunt resistors, or shunt reactors, and then the break-down could be extended to the whole matrix-type SFCL. Through these results, we found that the number of superconducting elements connected in series and parallel should be designed with enough margins against the break-down of superconducting elements and optimal conditions for shunt resistors and reactors should be determined. [ABSTRACT FROM AUTHOR]

Highlights: [•] The superconducting element reduced only the peak value of initial fault current. [•] The normal conductivity element limited the fault current after switching operation. [•] The burden of the superconducting element was significantly reduced. [•] The normal conductivity element performed current limiting operation stably. [ABSTRACT FROM AUTHOR]

Highlights: [•] Fault current limiter was used a high-speed interrupter. [•] High-speed interrupter was operated to bypass to the current limiter line. [•] The size of the fault current was limited to about 80% after the fault occurred. [•] The fault current was limited quickly within a half-cycle after the fault occurred. [ABSTRACT FROM AUTHOR]

Abstract: In a transformer-type superconducting fault current limiter (SFCL) with a neutral line, which is connected between the superconducting elements and secondary windings, we verified that the SFCL has excellent characteristics that induce the perfect simultaneous quench of the superconducting elements in the previous study. The application of the SFCL to the power networks requires its coordination with the reclosing operation duty, which protects a circuit. In this study, the fault current limiting and recovery characteristics of superconducting elements in the three-phase transformer-type SFCL with the neutral line were analyzed. The limiting rate of the fault current in the transformer-type SFCL could increased by an iron core, which allows quenching of the superconducting elements in a sound phase as well as in a faulted phase. In addition, the simultaneous quench led to uniform burdens on superconducting elements, all of which recovered their superconducting state within an opening cycle of a circuit breaker. Thus, the transformer-type SFCL with the neutral line could reliably conduct the fault current limiting and recovery operations of superconducting elements according to the reclosing operation duty and fault types. [Copyright &y& Elsevier]

Abstract: A transformer-type superconducting fault current limiter (SFCL) can control fault current by adjusting a turn’s ratio of the primary and secondary windings. In addition, by inserting a neutral line into the secondary winding, the power burden of the superconducting elements can be evenly distributed. We compared the operating and transient characteristics of the three-phase resistive and transformer-type SFCLs in the balanced and unbalanced faults that occur in power systems. In transformer-type SFCLs, where the primary and secondary windings of each phase were connected to one iron core, flux was induced to each winding of the normal phases by the fault current of the fault phase, thus causing simultaneous quench between superconducting elements. In the three-phase power systems, however, when faults occurred in more than two phases, the flux from fault current of the fault phase affected the other normal phase, thus decreasing the reduction ratio of fault current. We confirmed, however, that the fault current was reduced by 70% relative to cases without SFCLs. The results of the analysis of the transient characteristics of the three-phase transformer-type SFCL through the symmetrical component calculus showed that in the case of triple line-to-ground fault, a difference between positive and negative phase currents was large enough to cause an increase in the phase angle (δ) between the generator creating the power and the motor acting as a load. Thus, we expect that the transient stability deteriorates. [ABSTRACT FROM AUTHOR]

Abstract: A three-phase matrix-type superconducting fault current limiter (SFCL) with the 1×3 structure comprised of a trigger part and a current-limiting part was designed and manufactured. The trigger part, which is comprised of a superconductor and an reactor connected in parallel, improves the critical property of the superconductor by applying the external magnetic field to the superconductor, and the current-limiting part limits the fault current. In case of a single line-to-ground fault in the three-phase resistor-type SFCL, only two out of three superconductors were quenched, with large difference between them in resistance and power consumption. The three-phase matrix-type SFCL reduced the difference in the voltages generated from the quenched superconductors because the critical property was improved by applying the external magnetic field to the superconductors. In addition, the results showed that the power consumption was almost uniformly distributed in the superconductors. [Copyright &y& Elsevier]

Abstract: The breaking capacity of circuit breakers currently reaches the saturation point in electric power systems when a fault occurs. This is because the fault current increases due to continuous increases in electric power demand and facilities. It is not efficient to change existing circuit breakers, however, because of some problems that will increase the replacement cost and cause technical difficulties. To solve such problems, a study on the superconducting fault current limiter (SFCL) is being actively conducted. In this paper, a three-phase flux-coupling-type SFCL was composed, and its recovery characteristic according to the change in the number of turns of its secondary coils and its reclosing operation were analyzed. The increase in the number of turns of the SFCL’s secondary coils enhances its limiting efficiency by increasing its total impedance. The recovery time was delayed, however, when the number of turns of the secondary coils increased, because the superconducting element was connected in parallel to the secondary coils, which increased the voltage and current of the superconducting element. In other words, the delay in the recovery time was due to the increase in the power burden between the superconducting elements. Thus, two superconducting elements that were connected in series were used to distribute the power burden to each other, and the recovery characteristics of the SFCL with and without a neutral line were experimented on. [Copyright &y& Elsevier]

Abstract: The amount of consumed power is increasing with industrial development and rapidly increasing population. In accidents due to increased power consumption, the fault current sharply increases. Superconducting fault current limiters (SFCL) are studied widely to limit such fault currents. In this study, the characteristics of a transformer-type SFCL are analyzed depending on reclosing in changing the number of secondary winding turns. For experiment conditions, the turn ratio of the primary and secondary windings of a transformer-type SFCL was set to 4:2 and 4:4. The voltage was incremented by 80V from 120V for the experiment. The circuit breaker was operated with two open times of CO-0.17s –CO-0.17s –CO seconds (C; closed, O; open), respectively. Comparing the result for the experiment conditions with the case of the turn ratios of the primary and secondary windings at 4:4 and 4:2, the fault current was limited effectively in 4:2 than in 4:4 for the fault current limit ratios. With respect to the result of recovery characteristics, it was examined that the superconducting unit recovered faster when the turn ratio of the primary and secondary windings was 4:2 than 4:4. Comparing the amount of consumed power related to the recovery characteristics of the superconducting element, it was examined that the recovery time was faster in less power consumption for the superconducting unit. As such, since a transformer-type SFCL depending on reclosing in changing the number of turns of the secondary winding controls the turn ratio of the secondary winding to control fault current limiting and recovery characteristics, it can normally operate. [Copyright &y& Elsevier]

Abstract: We reported the fabrication and analysis of the reactor for matrix-type superconducting fault current limiters (SFCLs). Reactors take a role of inducting magnetic field to superconductors in reactors and bypassing partial fault currents to themselves. Superconductors used in this work were YBCO thin films deposited on 5.08cm diameter Al2O3 substrates. Also, reactors with a diameter of 90mm and a length of 230mm were fabricated. Then, we constructed the matrix-type SFCLs with a reactor which consists of a trigger part and current limiting parts. Experimental results are reported in terms of the characteristics of fault current in superconductors and reactors, and distribution of the fault power between them. [Copyright &y& Elsevier]

Abstract: In this paper we analyzed recovery characteristics of matrix-type SFCLs (MFCL) with 2×3 matrixes when triple lines-to-ground fault occurred. MFCLs used in this work consist of 18 superconductors, six reactors for induction of magnetic field and several parallel impedances for bypassing fault currents. Also we analyzed recovery characteristics of resistive-type SFCLs of which 18 superconductors are connected in series and parallel, without reactors and parallel impedances, for the purpose of comparison, under the same experimental conditions of MFCLs. Experimental results were reported in terms of recovery characteristics for individual superconductors in an R phase, dependency of faults cycles and applied fault voltages in each phase. We confirmed that recovery characteristics of MFCLs were more excellent than those of resistive-type SFCLs. [ABSTRACT FROM AUTHOR]