• The Transactions of the Korean Institute of Electrical Engineers B
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• v.52 no.11
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• pp.557-562
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• 2003

To develop a stable and compact small-sized superconducting magnetic energy storage (SMES) system, which provides electric power with high quality to sensitive electric loads, we fabricated a SMES coil and tested it. Because such a large-sized superconducting coil quenches far away from its critical current, the recovery current is frequently used as a stability criterion in the coil fabrication. Therefore, we first investigated the recovery current characteristics of the large current conductor, which was used in our SMES coil fabrication. The test results indicate that the recovery currents measured in the conductor are nearly identical to those based on the single wire. This implies that the recovery current is affected by the conductor's cooling condition rather than its size and current capacity. In the SMES coil test the first quench occurred at 1250 A, which is equivalent to the stored energy of about 2 MJ. It corresponds to the quench current density of about $130A/mm^2$ This value is much higher in comparison with that reported in the other work. In addition, the first quench current of the coil agrees well with the measured recovery current of the conductor having similar cooling condition with it. This means that to determine the recovery current of a conductor is, first of all, important in the design and fabrication of a large-sized superconducting coil.

• Proceedings of the Korea Institute of Applied Superconductivity and Cryogenics Conference
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• 1999.02a
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• pp.134-137
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• 1999

This paper describes the design, code of a $\mu$SMES device that we developed. The 0.7MJ $\mu$SMES coil was wound with high winding tension of about 14kbf/$mm^{2}$ in order to prevent wire motion from Lorentz force. This coil was charged up to a current of 1820A with a ramping rate of about 10A/s, where a quench occurred. This quench current is sbout 82% fo the coil critical current.

• Progress in Superconductivity and Cryogenics
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• v.17 no.2
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• pp.41-44
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• 2015

Critical current of high-temperature superconducting (HTS) coil is influenced by its own self magnetic field. Direction and density distribution of the magnetic field around the coil are fixed after the shape of the coil is decided. If the entire part of the HTS tape has homogeneous $I_c$ distribution characteristic, quench would be initiated in fixed location on the coil. However, the actual HTS tape has inhomogeneous $I_c$ distribution along the length. If the $I_c$ distribution of the HTS tape is known, we can expect the spot within the HTS coil that has the highest probability to initiate the quench. In this paper, $I_c$ distribution within the HTS coil under self-field effect is simulated by MATLAB. In the simulation procedure, $I_c$ distribution of the entire part of the HTS tape is assume d to follow Gaussian-distribution by central limit theorem. The HTS coil model is divided into several segments, and the critical current of each segment is calculated based on the-generalized Kim model. Single pancake model is simulated and self-field of HTS coil is calculated by Biot-Savart's law. As a result of simulation, quench-initiating spot in the actual HTS coil can be predicted statistically. And that statistical analysis can help detect or protect the quench of the HTS coil.

• Progress in Superconductivity and Cryogenics
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• v.6 no.2
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• pp.11-14
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• 2004

YBCO thin films have good characteristics for current limiting materials due to compact size and high current carrying capability. But the irregularities and the extreme thin thickness of YBCO films cause some difficulties in simultaneous quench and thermal shock protection. In order to solve these problems, vertical magnetic field generated from solenoid coil was applied to the YBCO element. And also to minimize the inductance caused by the serial connection of magnetic field source with superconducting elements, magnetic field source was separated from the power lines adapting protective current transformer. In this study, electric field-current (E-I) and quench characteristics of YBCO films were analyzed both by electrical measuring method and observations of bubble propagation. From the experiment results, it was revealed that the magnetic fields generated by surrounding coil could induce the uniform quench distribution for all stripes of current limiting units and finally simultaneous quenches were realized in all serial connection of YBCO elements. In addition, the separation of magnetic field source form electrical network could be good solution for simultaneous quench of YBCO films without any unnecessary effect caused by serial connection.

• Proceedings of the KIEE Conference
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• 2005.07b
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• pp.1252-1254
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• 2005

High Tc superconducting(HTS) model coil was prepared. Current-voltage(I-V) characteristic curves of model coil, sub-coils and joints were investigated at 77K and other some temperatures. Cooling system for characteristics measurement was made by using G-M cryocooler. At 77K, quench current(Iq) of model coil was 43.9A and the lowest Iq of sub-coils was 38.8A. At 55K, sub coil SP #06 was 106A. So, 100A was chosen as the operating current at 55K with margin. Joule heat of model coil was 0.65W at 100A, operating current and 58K. Joint resistances between sub-coils were about $70n{\Omega}$ at 77K and about $30n{\Omega}$ at 55K.

• Progress in Superconductivity and Cryogenics
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• v.8 no.4
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• pp.22-25
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• 2006

This paper deals with the computation of the current limiting behavior of high-temperature superconducting (HTS) modules for the superconducting fault current limiter (SFCL). The SFCL module consists of a monofilar type BSCCO-2212 tube and a shunt coil made of copper or brass. The shunt coil is connected to the monofilar superconducting tube in parallel. Through analysis of the quench behavior of the monofilar component with shunt coils, it is achieved to drive an equivalent circuit equation from the experimental circuit structure. In order to analyze the quench behavior of the SFCL module, we derived a partial differential equation technique. Inductance of the monofilar component and the impedance of the shunt coil are calculated by Bio-Savart and Ohm's formula, respectively. We computed the quench behavior using the calculated values, and compared the results with experimental results for the quench characteristics of a component. The results of computation and test agreed well each other, and it was concluded that the analytic result could be applied effectively to design of the distribution-level SFCL system.

• Proceedings of the KIEE Conference
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• 2001.07b
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• pp.726-728
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• 2001

For the development of a small-sized superconducting magnetic energy storage (SMES) system we designed, fabricated and tested the model coil consisting five coils with different features, e.g. winding tensions, bore diameters and materials, cooling channels. The results show that even in the highly pre-stressed small coil A, about 70 % of the coils critical current are degraded. The quench current of the coils A, B and E with narrow cooling channels is two times as high as that of the coil C without them though they are similar except spacers. The test results also indicate that the usual training effect depends on the winding tensions of the coils but the quench characteristic does not change according to materials of a bobbin.

• Proceedings of the KIEE Conference
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• 1998.07a
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• pp.104-106
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• 1998

For the development of the 0.7 MJ small-sized superconducting magnetic energy storage (${\mu}$SMES) device, quench currents of a kA class superconducting cable were tested for various winding tensions because a dry superconducting coil is usually quenched by an abrupt heat pulse due to strand motions. The test coil similar to parameters of the optimally designed 0.7 MJ ${\mu}$SMES except a stored energy and a size was fabricated based on the test results of the kA class superconducting cable and tested. These experimental results show that the highly prestressed test coil has an excellent DC performance in spite of a dry type coil but its quench current is much degraded even at the low field ramping rate of about 0.4 T/s.

• 한국초전도학회:학술대회논문집
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• v.15
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• pp.79-79
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• 2005

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2005.11a
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• pp.165-166
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• 2005

In this paper, we investigated the quench generation of HTSC elements in fault types according to inductance variation in the integrated three-phase flux-lock type SFCL. The integrated three-phase flux-lock type SFCL was the upgrade version of the single-phase flux-lock type SFCL. The structure of the integrated three-phase flux-lock type SFCL consisted of three-phase flux-lock reactor wound on an iron core with the ratio of the same turn between coil 1 and coil 2 in each phase. When the SFCL is operated under the normal condition, the flux generated in the iron core is zero because the flux generated between two coils of each single phase is canceled out. Therefore, the SFCL's impedance is zero, and the SFCL has negligible influence on the power system. However, if a fault occurs in any single-phase among three phases, the flux generated in the iron core is not zero any more. The flux makes HTSC elements of all phases quench irrespective of the fault type, which reduces the current of fault phase as well as the current of sound phase. It was observed that the fault current limiting characteristics of the suggested SFCL were dependent on the quench characteristics of HTSC elements in all three phases.