• 한국초전도ㆍ저온공학회논문지
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• 제18권2호
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• pp.18-20
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• 2016

The study of superconducting fault current limiter (SFCL) is continuously being studied as a countermeasure for reducing fault-current in the power system. When the fault occurred in the power system, the fault-current was limited by the generated impedance of SFCLs. The operational characteristics of the flux-offset type SFCL according to turn ratios between the primary and the secondary winding of a reactor were compared in this study. We connected the secondary core to a superconductor and a SCR switch in series in the suggested structure. The fault current in the primary and the secondary winding of the reactor and the voltage of the superconductor on the secondary were measured and compared. The results showed that the fault current in the load line was the lowest and the voltage applied at both ends of the superconductor was also low when the secondary winding of the reactor had lower turn ratio than the primary. It was confirmed based on these results that the turn ratio of the secondary winding of the reactor must be designed to be lower than that of the primary winding to reduce the burden of the superconductor and to lower the fault current. Also, the suggested structure could increase the duration of the limited current by limiting the continuous current after the first half cycle from the fault with the fault current limiter.

• 한국초전도저온공학회:학술대회논문집
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• 한국초전도저온공학회 1999년도 제1회 학술대회논문집(KIASC 1st conference 99)
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• pp.97-100
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• 1999

Nowadays the high-Tc Superconducting Fault current Limiter (SFCL) is one of the superconducting devices which are very closed to commercialization. The most popular model of High-Tc SFCL is a magnetic shielding type. A superconductor of magnetic shielding type SFCL can be stable in the superconducting state, because there is no contact between the superconductor and the normal conductor. But this model needs large place to set up and in a fault condition, mechanical vibrations may happen to damage the superconductor or total device. In this paper, to solve these problems, the simplified model of magnetic shielding type SFCL was introduced.

• 전기학회논문지
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• 제60권2호
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• pp.239-244
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• 2011

Due to large demand, the increase of fault current has caused the capacity of power machines in power grid to increase. Among several countermeasures, the superconducting fault current limiter (SFCL) has been noticed as one of the promising countermeasures to solve these problems. However, in spite of excellent current limiting performances of the SFCL, the application of SFCL to power system has been delayed due to both the limited space for the SFCL's installation and its longer recovery time after the fault removal. In order to solve these problems, a hybrid type SFCL was developed. In this paper, we studied the operation characteristics of the hybrid SFCL with first half cycle non-limiting operation by modelling using PSCAD/EMTDC and experiment. It was shown through the simulation using PSCAD/EMTDC and the simulated experiment that the fault current limiting and the fast recovery operations of the hybrid SFCL with the first half cycle non-limiting operation were achieved.

• 한국초전도ㆍ저온공학회논문지
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• 제19권4호
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• pp.40-44
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• 2017

This paper analyzed the fault current limiting characteristics of the previously proposed transformer superconducting fault current limiter (TSFCL) interruption system according to its transformer type. The TSFCL interruption system is an interruption technology that combines a TSFCL, which uses a transformer and a superconductor, and a mechanical DC circuit breaker. This technology first limits the fault current using the inductance of the transformer winding and the quench characteristics of the superconductor. The limited fault current is then interrupted by a mechanical DC circuit breaker. The magnitude of the limited fault current can be controlled by the quench resistance of the superconductor in the TSFCL and the turns ratio of the transformer. When the fault current is controlled using a superconductor, additional costs are incurred due to the cooling vessel and the length of the superconductor. When the fault current is controlled using step-up and step-down transformers, however, it is possible to control the fault current more economically than using the superconductor. The TSFCL interruption system was designed using PSCAD/EMTDC-based analysis software, and the fault current limiting characteristics according to the type of the transformer were analyzed. The turns ratios of the step-up and step-down transformers were set to 1:2 and 2:1. The results were compared with those of a transformer with a 1:1 turns ratio.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2004년도 하계학술대회 논문집 Vol.5 No.1
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• pp.547-550
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• 2004

Superconducting fault current limiter(SFCL) is expected to be introduced into electric power system in future as an effective countermeasure for the increase of the short-circuit current due to the growth of the electric power system. SFCL has a merit that the fault current can be limited by the resistance generated when a superconductor transits from a superconducting state to a normal state without additional detecting device. In this paper, we investigated the resistance variance of resistive type SFCL and the fault current limiting characteristics due to the amplitude of source voltage. We could obtain the more effective fault current limiting characteristics of SFCL as the source voltage increased.

• 전기학회논문지
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• 제65권5호
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• pp.873-877
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• 2016

This paper proposed the structure that applied superconductors to the neutral line of a transformer and applied the normal conductors to the third line. The superconductor applied to the neutral line of a transformer limited the peak value of initial fault current, while the normal conductor finally limited the fault current. In order to secure the operating reliability of transformer type Superconducting Fault Current Limiter (SFCL) of previously proposed structure, we analyzed the operating characteristics according to the fault types. We tested a line-to-ground fault and a line-to-line fault. As a result of the experiment, all the faults showed that the superconductor stably limited the peak-value of initial fault current. Also, the normal conductor finally limited the fault current. Based on this research results, We thought that if the structure of inserting superconductor into the neutral line is applied to the real system, it could improve the reliability and stability of the power system.

• Journal of Electrical Engineering and Technology
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• 제7권5호
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• pp.659-663
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• 2012

The application of large power transformer into a power distribution system was inevitable due to the increase of power demand and distributed generation. However, the decrease of the power transformer's impedance caused the short-circuit current of the power distribution system to be increase thus, the higher short-circuit current exceeded the cut-off ratings of the protective devices such as circuit breaker. To solve these problems, several countermeasures have been proposed to protect the power system effectively from higher fault current and the superconducting fault current limiter (SFCL) has been expected to be the promising countermeasure. In spite of excellent current limiting performances of the SFCL, on the other hand, the efforts to apply the SFCL into power system has been delayed due to both the limited spaces for the SFCL's installation and its long recovery time after the fault removal. In order to solve these problems, a hybrid SFCL, which can perform either first half cycle limiting of first half cycle non-limiting operation, has been developed by corporation of LSIS (LS Industrial System) and KEPCO (Korea Electric Power Corporation). In this paper, we tried to requirements hybrid SFCL by PSCAD/EMTDC. Simulation results of our analysis of the hybrid SFCL is that its accompanied the characteristics both the limit the fault current and quick recovery caused by the less impact from superconductor.

• 한국초전도ㆍ저온공학회논문지
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• 제9권4호
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• pp.32-36
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• 2007

We fabricated and tested a novel hybrid superconducting fault current limiter (SFCL) of three-phase $24kV_{rms}/630A_{rms}$ rating. In order to apply conventional resistive SFCLs into electric power systems, the urgent issues to be settled are as follows, such as initial installation price of SFCL, operation and maintenance cost due to ac loss of superconductor and the life of cryostat, and high voltage and high current problems. The ac loss and high cost of superconductor and cryostat system are main bottlenecks for real application. Furthermore in order to increase voltage and current ratings of SFCL, a lot of superconductor components should be connected in series and parallel which resulted in extreme high cost. In addition, the method to quench all components at the same instant needs very sophisticated skill and careful operation. Due to these problems, the practical applications of SFCL were pending. Therefore, in order to make practical SFCL, the price of SFCL should be lowered and should meet the demand of utilities. We designed novel hybrid SFCL which combines superconductor and conventional electric equipment including vacuum interrupter, power fuse and current limiting reactor. The main purpose of hybrid SFCL is to drastically reduce total usage of superconductor by adopting current commutation method by use of superconductor and high fast switch. Consequently, it was possible to get the satisfactory test results using this method, and further works for field tests are in the process.

• 전기학회논문지
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• 제64권4호
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• pp.612-615
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• 2015

This paper proposed an high-speed superconducting fault current limiter (H-SFCL). The proposed H-SFCL functioned the initial fault current could be covered by the SFCL and the continued fault current after the one-cycle from fault occurrence could be controlled current-limiting-element of the normal conduction. To investigate the operation characteristics of the H-SFCL, a simulation power system was constructed, and a single line-to-ground fault was occurred. As a result, the H-SFCL limited the fault current by more than about 70%, and it was confirmed that the electric power burden was reduced compared to the SFCL that consisted only of superconductors.

• 한국초전도ㆍ저온공학회논문지
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• 제17권3호
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• pp.57-61
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• 2015

A Superconducting Fault Current Limiter is an electric power device which limits the fault current immediately in a power grid. The SFCL must be cooled to below the critical temperature of high temperature superconductor modules. In general, they are submerged in sub-cooled liquid nitrogen for their stable thermal characteristics. To cool and maintain the target temperature and pressure of the sub-cooled liquid nitrogen, the cryogenic cooling system should be designed well with a cryocooler and coolant circulation devices. The pressure of the cryostat for the SFCL should be pressurized to suppress the generation of nitrogen bubbles in quench mode of the SFCL. In this study, we tested the performance of the cooling system for the prototype 154 kV SFCL, which consist of a Stirling cryocooler, a subcooling cryostat, a pressure builder and a main cryostat for the SFCL module, to verify the design of the cooling system and the electric performance of the SFCL. The normal operation condition of the main cryostat is 71 K and 500 kPa. This paper presents tests results of the overall cooling system.