• Progress in Superconductivity and Cryogenics
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• v.11 no.3
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• pp.20-25
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• 2009

The quench detection system of the KSTAR (Korea Superconducting Tokamak Advanced Research) primarily uses the resistive voltage measurement due to a quench. This method is to detect the resistive voltage generated by a quench, which is continuously maintained above the preset voltage threshold for a given holding time. As the KSTAR PF (Poloidal Field) coils are operated in the pulse current mode, the large inductive voltages are generated. Therefore the voltage threshold and the quench holding time should be determined by considering both the inductive voltages measured during the operation, and the maximum conductor temperature rise through the quench analysis. In this paper, the compensation methods for minimizing the inductive voltages are presented for the KSTAR PF coils. The quench hot spot analysis of the PF coils was carried out by the analytical and numerical methods for determining the proper values of the quench voltage threshold and the allowable quench protection delay time.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.13 no.4
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• pp.337-342
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• 2000

We fabricated resistive superconducting fault current limiters based on YB $a_{2}$/C $u_{3}$/ $O_{7}$ thin films and investigated their quench propagation characteristics. The YB $a_{2}$/C $u_{3}$/ $O_{7}$ films was coated with a gold layer and patterned into 1 mm wide meander lines by photolithography. The quench was concluded to start locally and propagates until completed. The quench propagation characteristics were explained based on the heat transfer within the film as well as between the film and the surrounding liquid nitrogen. The quench completion time depended strongly on potential fault current amplitude and not significantly on fault angle which indicates that the quench propagation speed is affected more by heat dissipation rate than by fault current increase rate. The quench completion time was 1 msec at the fault current of 65 $A_{peak/{\ak}}$.

• Progress in Superconductivity and Cryogenics
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• v.11 no.3
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• pp.6-9
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• 2009

The thermal characteristics of quench propagation is a crucial problem for the stability of the superconductor. The objective of this study is to simulate the quench propagation with the variation of disturbance energy in Bi-2223/Ag HTS pancake coil. In this analysis, the temperature-time trace of a point away from heater was calculated under conditions of different quench energy. The critical disturbance energy between quench propagation and quench recovering was calculated, In addition, the minimum quench energy with different transport currents was obtained through the present simulation. These results are significant to the application of HTS.

• The Transactions of the Korean Institute of Electrical Engineers B
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• v.49 no.9
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• pp.584-589
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• 2000

We fabricated resistive superconducting fault current limiters (SFCL) based on YBCO thin films grown on a 2-inch diameter Al2O3 substrate. The current limiting element was 1 mm wide and 260mm long meander line prepared by standard photolithography. The minimum quench current of the current limiting element was about 8 Apeak. This SFCL sucessfully controlled the fault current below 14.3 Apeak at the voltage of 100 Apeak which is otherwise to increase up to 141 Apeak. The quench completion time was less than 3 msec. The temperature of the current limiting element rose to about 200 K in 3 cycles after fault. The SFCL showed reproducible quench during hundreds times of repeated experiments.

• Proceedings of the KIEE Conference
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• 1997.07a
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• pp.270-272
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• 1997

Superconducting wire is quenching as soon as transport current exceeded the critical current value. However transport current exceeded the critical current value, quench is not generated immediately. In this paper, the results of the theoretical study for time delay of quench phenomenon are described.

• Proceedings of the KIEE Conference
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• 2006.07b
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• pp.711-712
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• 2006

For the application of superconducting fault current limiters(SFCLs) to the protection system, quench recovery characteristics of Au/YBCO thin film were investigated. The Au/YBCO thin film was designed as a SFCL element with a bi-spiral pattern. The SFCL element limited the fault current successfully. For the analysis of the recovery to superconducting state, we measured resistance variation of the SFCL element after the quench. In addition, in order to investigate the dependence of quench characteristics of SFCL on the $LN_2$ cooling condition, we measured the recovery time under a pressure of 1, 2 and 3 atm. As the results, the recovery time increased in proportion to the duration of the fault currents. In the sub-cooled condition, while the quench development was exactly the same, the recovery time was shortened as the pressure increased.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 1999.11a
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• pp.85-88
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• 1999

We fabricated resistive superconducting fault current lmiters based on YBa$_2$Cu$_3$O$_{7}$ thin films and investigated their quench propagation characteristics. The YBa$_2$Cu$_3$O$_{7}$ film was coated with a gold layer and patterned into 1 mm wide meander lines by photolithography. The limiters were tested with simulated fault currents of various fault angles and amplitudes. The quench propagation characteristics were explained based on the heat transfer within the film as well as between the film and the surrounding liquid nitrogen. The quench completion time strongly depended on the potential fault current. It was 1 msec at the peak fault current of 76 A/peak/ and corresponding quench propagation speed was 43 m/sec (film cross section: 4 x 10$^{-6}$ $\textrm{cm}^2$).

• The Transactions of the Korean Institute of Electrical Engineers B
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• v.48 no.10
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• pp.537-543
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• 1999

We fabricated a resistive superconducting fault current limiter (SFCL) of a meander type based on a YBCO film with the meander cross section of 5 $\times$ $10^{-6}$$cm^2$, and performed current limitation experiments. The film was coated quench current was 9.6 Apeak at 60 Hz, and the fast quench time was 0.63 msec. The resistance of the limiter continuously increased for three cycles dut to the temperature rise in the gold layer. The temperature of the current limiting element reached the room temperature in 11 msec, $150^{\circ}C$ in 54 msec after quench, and was saturated afterwards. For $45^{\circ}$and $90^{\circ}$faults the fast quench times were 0.56 msec and 0.26 msec, respectively. The quench time is believed to be reduced because the fault occurred when the current was either increasing or at the peak value. This limiter effectively limited the fault current to about 1/5 of the potential current with no SFCL right after the fault and to about 1/8.5 in three cycles. We confirmed that the gold layer effectively carried out the role of heat dissipation as the SFCL was quenched.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2003.05b
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• pp.16-19
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• 2003

YBCO film을 이용하여 2 stripe-meander 형태의 초전도 한류기를 제작하고 시험하였다. 초전도 film의 hot spot에 의해 발생하는 열을 분산시키기 위해 gold shunt layer를 입혔다. 사고각 $0^{\circ}$에서 사고발생 후 최초 quench 전류값은 $9.56A_{peak}$이었고 약 0.63 msec동안 fast quench 가 진행되고 이후에는 gold층의 열발생에 의한 저항증가가 약 3주기동안 진행된 후 안정되었다. 사고각 $45^{\circ}$와 $90^{\circ}$ 에서는 전류가 상승하는 도중 혹은 최고지점에서 사고가 발생했기 때문에 fast quench time이 각각 0.56 msec와 0.26msec를 보였다. 초전도 한류기를 적용하였을 때 사고전류는 사고직후 약 5배, 3주기후에는 약 8.5배까지 효과적으로 제한함을 알 수 있었다.

• Proceedings of the KIEE Conference
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• 1999.07a
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• pp.277-280
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• 1999

We fabricated a resistive superconducting fault current limiter of two stripe meander type based on a YBCO film, and performed current limitation experiments. In order to disperse the heat generated at hot spots in the YBCO film the film was coated with a gold shunt layer. At $0^{\circ}$ fault angle the minimum quench current was $9.6 A_{peak}$(meander line cross section: $5{\times}10^{-6}cm^2$) and the fast quench time was 0.63 msec. The resistance of the limiter continued to increase for three cycles due to heat generation in the gold layer and was stabilized afterwards. At $45^{\circ}$ and $90^{\circ}$ the fast quench time were 0.56 msec and 0.26 msec, respectively. The quench time is believed to be reduced because faults occurred when the current was increasing or was at the peak value. With the limiter we could effectively limit the fault current about 1/5 times right after the fault and about 1/8.5 times three cycles after.