• Progress in Superconductivity
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• v.6 no.2
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• pp.113-117
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• 2005

In this study, electromagnetic analysis of current paths including meander pattern, spiral pattern, and bi-spiral pattern were performed and in order to verity the analysis results, experiments tests including quench test, and insulation tests were performed. In addition, bubble corner concepts were introduced to enhance insulation reliability. From our study, bi-spiral pattern of YBCO thin films were rather effective for quench and insulation than the other patterns. So this current path pattern was adopted for YBCO thin films in order to develop 6.6 kV resistive fault current limiters. Finally YBCO thin films were connected in series and parallel to enhance capacity, and the test results of current limiting characteristics of 6.6kV resistive SFCL were successful. The Progress in Superconductivity is published every six month and serves as a channel for publications on superconductivity and related topics. The author(s) are required to submit THREE copies of the manuscripts along with original figures directly to the Editor.

• The Transactions of the Korean Institute of Electrical Engineers A
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• v.49 no.8
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• pp.418-423
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• 2000

In this paper, we reported the current limiting properties of superconducting fault current limiters (SFCL). Our SFCL was patterned in a coil-type on a YBCO film deposited using rf sputtering techniques and was coated with a gold shunt layer in order to disperse the heat generated at hot spots in the YBCO film. Current increased up to 13.5 Apeak at 60 Hz for the voltage of 11.5 Vpeak, which is the minimum quench point, and increased up to 17.6 Apeak at 60 Hz for the voltage of 80 Vpeak. The quench completion time was 5 msec at 11.5 Vpeak and 4 msec at 80 Vpeak respectively. We think that this architecture using coil-type SFCL can be useful for the protection of the power delivery systems from fault currents.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2004.05b
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• pp.169-172
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• 2004

We present the basic properties of a superconducting current limiting fuse (SCLF) based on YBCO/Au films. The SCLFs consists of YBCO stripes covered with Au layers for current shunt. Under the source voltage of 100 $V_{rms}$, the longer the duration time of fault current was, the shorter its discharge time was. The duration time of fault current and its discharge time were reduced by increased voltages in the range of 200 - 300 $V_{rms}$. We thought that this was because the quench propagation was limited by local melting generated with higher voltage.

• 한국초전도학회:학술대회논문집
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• v.10
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• pp.272-275
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• 2000

We investigated a resistive superconducting fault current limiter (SFCL) fabricated using YBCO thin films on 2-inch diameter sapphire substrates. Nearly identical SFCL units were prepared and tested. The units were connected in series and parallel to increase the current and voltage ratings. A serial connection of the units showed significantly unbalanced power dissipation between the units. This imbalance was removed by introducing a shunt resistor to the firstly quenched unit. Parallel connection of the units increased the current rating. An SFCL module of 4 units in parallel, each of which has minimum quench current 25 Ap, was produced and successfully tested at a 220 V circuit. From the resistance increase, we estimated that the film temperature increases to 200 K in 5 msec, and 300 K in 120 msec. Successive quenches revealed that this system is stable without degradation in the current limiting capability under such thermal shocks as quenches at 220 V.

• Proceedings of the KIEE Conference
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• 2007.07a
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• pp.941-942
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• 2007

The superconducting fault current limiter (SFCL) consists of superconducting coil for limiting the fault current and cryogenic cooling system for keeping the coil in superconducting condition. The study on the insulation design for superconducting coil and cryogenic cooling system should be elaborately performed to develop a high voltage SFCL. In this paper, insulation design of solenoid coil for 13.2kV/630A SFCL is performed through the AC dielectric breakdown test and lightning impulse dielectric strength test. The dependence of dielectric characteristics on the magnitude of liquid nitrogen pressure is also investigated. Through the investigation, it is verified that dielectric characteristics of sub-cooled nitrogen are strongly enhanced by the pressurization. The electrical insulation design of 13.2kV/630A SFCL is performed by applying the experimental results. The successful insulation design for development of 13.2kV/630A SFCL is confirmed by AC dielectric breakdown tests.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2006.06a
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• pp.251-252
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• 2006

As one of methods to increase the voltage rating of the flux-lock type SFCL, the fault current limiting characteristics of the flux-lock type SFCL with HTSC elements connected in series were analyzed. The initial fault current amplitudes in two SFCLs with the series connection of two HTSC elements and with single HTSC element were the same. In addition, the resistance amplitude of each HTSC element in SFCL with the series connection of two HTSC elements had the similar one in SFCL with single HTSC element. With increase of applying voltage, the unbalance of voltage between two HTSC elements in SFCL with the series connection of two HTSC elements disappeared.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.23 no.1
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• pp.42-47
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• 2010

The power burden of high-$T_c$ superconducting (HTSC) elements comprising superconducting fault current limiter (SFCL) using magnetic coupling of shunt reactors was analyzed. The magnetically coupled shunt reactors play a role in distributing the even power burden between HTSC elements comprising the SFCL, which contributes to the effective current limiting and recovery characteristics of the SFCL. It was confirmed through the comparative analysis on the SFCLs with both the magnetically coupled and the magnetically uncoupled shunt reactors that the magnetically coupled shunt reactors could improve the SFCL's performance by equalizing the power burden of HTSC elements.

• Proceedings of the KIEE Conference
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• 2006.04b
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• pp.393-395
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• 2006

We investigated the operational characteristics of the hybrid-type superconducting fault current limiter (SFCL) according to the serial and parallel connections of secondary circuits. The hybrid-type SFCL consists of a transformer, which has a primary winding and several secondary windings with $YBa_2Cu_3O_7$ films connected in series and parallel. In order to increase the capacity of the SFCL, the serial connection between each current limiting unit is necessary. The hybrid-type SFCL with the serial connection in secondary circuits could show superior characteristics than those of the parallel connections in the current limiting and quench time. The resistances generated in the superconducting units were also lowered at the parallel connections. We confirmed that the parallel connection reduced the power burden of each superconducting unit under the same conditions because of the simultaneous quenching between superconducting units.

• The Transactions of the Korean Institute of Electrical Engineers A
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• v.55 no.2
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• pp.62-66
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• 2006

We investigated the characteristics of the hybrid-type superconducting fault current limiter (SFCL) by the number of secondary windings. The SFCL consists of a transformer, which has a primary winding and several secondary windings with serially connected $YB_{a2}Cu_{3}O_{7}$ films. In order to increase the capacity. of the SFCL, the serial connection between each current limiting unit is necessary. Resistive-type SFCL has a difficulty in quenching simultaneously between the units due to slight differences of their critical current densities. The hybrid-type SFCL could achieve the simultaneous quenching through the electrical isolation and the mutual flux linkage among the units. We confirmed that the capacity of the SFCL could be increased effectively through the simultaneous quenching among the units. In addition, the power burden of the system could be reduced by adjusting the number of secondary windings. We will investigate the method to increase the capacity through serial and Parallel connections among current limiting units.

• Proceedings of the KIEE Conference
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• 2006.10b
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• pp.208-211
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• 2006

We have analyzed operating characteristics of hybrid-type superconducting fault current limiter (SFCL) according to the parallel connection of secondary windings with $YBa_{2}Cu_{3}O_{7}$ (YBCO) films. The turn ratio between the primary and secondary windings of each reactor was 63:21. Hybrid-type SFCL using a transformer with parallel reactors could reduce the unbalanced quench caused by differences of the critical current density between YBCO films. We found that hybrid-type SFCL having parallel connection induced simultaneous quench between the superconducting elements. The quench-starting point at this time was almost same. When the applied voltage was 200V, the limiting current in the hybrid-type SFCL with a serial connection was lowered to 34 percent than that in the SFCL with a parallel connection. In the meantime, when the voltage generated in the superconducting elements was the same, the current value in the parallel connection was 60 percent less than in the serial connection. The voltage generated in the primary winding also showed the similar behavior. In conclusion, we found that the fault current was limited more effectively in the SFCL with the serial connection but the power burden of the superconducting elements was reduced in the parallel connection.