• Proceedings of the KIEE Conference
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• 2008.07a
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• pp.2212-2213
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• 2008

In this paper, we studied the method for simultaneous quenching of a transformer type superconducting fault current limiter (SFCL) with two superconducting elements connected in series. Only an element between two elements of the transformer type SFCL was quenched like the case of the resistive type SFCL. By this quenching characteristics, the power burden of the superconducting element was increased. In order to solve this problem, we connected the neutral line between two superconducting elements and the center of secondary coils. The two elements were all quenched in the transformer type SFCL with a neutral line. As a result, the power burden of superconducting elements was decreased, so it was efficient for the increase of power capacity of the transformer type SFCL.

• The Transactions of the Korean Institute of Electrical Engineers P
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• v.57 no.3
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• pp.323-327
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• 2008

We investigated the quench characteristics of a flux-lock type superconducting fault current limiter (SFCL) depending on the methods of the serial and parallel connections between the superconducting elements. The flux-lock type SFCL consists of two coils. The primary coil is wound in parallel to the secondary coil through an iron core, and the secondary coil is connected to the superconducting elements in series and parallel. In this paper, the analyses of voltage, current, and resistance of the superconducting elements connected in serial and parallel were performed to increase the power capacity of the flux-lock type SFCL. A part of the superconducting elements was not quenched in $2{\times}2$ serial connection between the elements and then the power burden of the quenched elements was increased. However the elements with $2{\times}2$ parallel connection was all quenched. This means that the power burden of each superconducting element can be reduced under the same conditions. We found that $2{\times}2$ parallel connection was more profitable for the current limiting effects and the increase of the power capacity.

• Proceedings of the Korean Institute of IIIuminating and Electrical Installation Engineers Conference
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• 2006.05a
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• pp.432-434
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• 2006

We investigated the quench characteristics of a flux-lock type superconducting fault current limiter (SFCL) according to the number of the superconducting elements at the subtractive polarity winding of a transformer. The flux-lock type SFCL consists of the transformer with a primary winding and two secondary windings connected in parallel, and the superconducting element was connected with secondary winding in series, respectively. The applied voltage at that tin was 200V. when two superconducting elements of the secondary winding was connected in parallel, the peak lie current increased up to 99A, while that flowing in a superconducting element in conventional flux-lock type SFCL showed 50A under the same conditions, the impedance of secondary winding under the same situation showed the opposite behavior. This enabled the parallel structure to be easy to increase the capacity of power system, in the meantime, The quench between two superconducting elements in the SFCL with two secondary windings connected in parallel was achieved simultaneously. While the quench-starting point was slightly different in the SFCL with two superconducting elements connected in series. We found that the parallel connection between the secondary windings increased the power capacity and let quench characteristics improve through their mutual linkage.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.60 no.5
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• pp.1073-1077
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• 2011

The breaking capacity of circuit breakers could be no more increased in the electric power system. This is because the fault current increases due to continuous increases in electric power demand and facilities. To solve the problem, it is necessary to come up with an alternative. The superconducting fault current limiter (SFCL) has received an attention among various alternatives. The SFCL effectively reduce a fault current in cooperation with a power circuit breaker. A various types of the SFCL are suggested and a study on them have been progressed. As a result of it, the SFCL can be applyed to the electric power system in the near future. But, a study on recovery behaviors of the SFCL is not enough for applying to the electric power system. If the superconducting elements do not completely recover to the superconducting state after fault operation, it might be a breakdown of the superconducting elements due to heavy power burden and it gives an bad influence on the working of other electric devices. Additionally, the distribution power system has reclosing operation such as open-0.3sec-closed/open-3min-closed/open procedure. So we need to study more about improvement of the recovery behaviors of the SFCL. In this paper, we analyzed the recovery behaviors of a flux-coupling type SFCL according to reclosing operation when a single line-to-ground fault occurred and we compared recovery behaviors of the SFCL with and without a neutral line between secondary reactors and superconducting elements. Also, the flux-coupling type SFCL has advantageous for increases of capacity by controlling the variation in turn ratios between two reactors. Consequently, when the number of turns of the secondary reactors increased, the power burden of the superconducting elements was bigger due to the increase of impedances of the secondary reactors. To distribute the power burden, two superconducting elements connected in series and the balanced quenching of the superconducting elements was induced by connecting a neutral line.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.28 no.7
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• pp.62-68
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• 2014

We proposed a series connection-type superconducting fault current limiter(SFCL) using E-I core that can prevent the internal magnetic flux generation of cores during normal operation, and prevent the saturation of cores due to a sudden magnetic flux generation at the initial stage of fault occurrence while limiting the peak current. Through a short-circuit simulation experiment, we analyzed the operating status of the two superconducting elements and limiting characteristics according to the size of the fault current peak before and after the failure. Further, the double peak current limiting characteristics according to the winding directions as well as the current and the voltage of each coil were compared and analyzed.

• The Transactions of the Korean Institute of Electrical Engineers P
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• v.57 no.2
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• pp.198-201
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• 2008

We investigated the operating characteristics of the flux-lock type superconducting fault current limiter(SFCL) with the parallel connection between the primary and secondary windings which are connected with two superconducting units in series. The parallel connection for current level increase of the flux-lock type SFCL is necessary to apply the SFCL into the power system. The resistance generated in superconducting units was dependent upon the winding direction of the primary and the secondary coils, which can reduce the power burden. The resistance of the superconducting elements in the subtractive polarity winding is higher than that of the additive polarity winding. The fault current limiting effect of the subtractive polarity winding is better than that of the additive polarity winding. From this results, we confirmed that the power capacity of the flux-lock type SFCL could be increased by the parallel connection of the superconducting units.

• Proceedings of the Korean Institute of IIIuminating and Electrical Installation Engineers Conference
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• 2007.05a
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• pp.229-230
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• 2007

We investigated the quench characteristics of a superconducting element, two superconducting elements in order to increase the current capacity of flux lock type SFCL. The flux-lock type SFCL consisted of the transformer with a primary winding and a secondary winding connected in parallel, and the superconducting element was connected with secondary winding in series. The applied voltage at that time was 160 ${\sqrt{3}}$. We found that the parallel connection between the superconducting elements increased the power capacity and let quench characteristics improve through their mutual linkage.

• Progress in Superconductivity and Cryogenics
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• v.19 no.2
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• pp.44-47
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• 2017

In this paper, the current limiting characteristics of the transformer type superconducting fault current limiter (SFCL) with the two coupled secondary windings due to its winding direction were analyzed. To analyze the dependence of transient fault current limiting characteristics on the winding direction of the additional secondary winding, the fault current limiting tests of the SFCL with an additional secondary winding, wound as subtractive polarity winding and additive polarity winding, were carried out. The time interval of quench occurrence between two superconducting elements comprising the transformer type SFCL with the additional secondary winding was confirmed to be affected by the winding direction of the additional secondary winding. In case of the subtractive polarity winding of the additional secondary winding, the time interval of the quench occurrence in two superconducting elements was shorter than the case of the additive polarity winding.

• The Transactions of the Korean Institute of Electrical Engineers A
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• v.55 no.8
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• pp.329-333
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• 2006

We investigated the quench characteristics of a flux-lock type superconducting fault current limiter (SFCL) depending on the number of the serial connection between the superconducting elements at the subtractive polarity winding of a transformer. The flux-lock type SFCL consists of two coils. The primary coil is wound in parallel to the secondary coil through an iron core, and the secondary coil is connected to the superconducting elements in series. The operation of the flux-lock type SFCL can be divided into the subtractive and the additive polarity windings depending on the winding directions between the primary and secondary coils. In this paper, the analyses of voltage, current, and resistance of superconducting elements in serial connection were performed to increase the power capacity of flux-lock type SFCL. The power burden was reduced through the simultaneous quenching between the superconducting elements. This enabled the flux-lock type SFCL to be easy to increase the capacity of power system.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.16 no.12S
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• pp.1286-1291
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• 2003

Quench behavior of resistive superconducting fault current limiters (SFCLS) with various pattern shapes was investigated. The pattern shapes employed were meander, bi-spiral, and spital shapes of identical line width, gap and margin. SFCLS were fabricated from YBCO thin films grown on two-inch diameter Al$_2$O$_3$ substrates under the same conditions. The total length of current limiting paths was the shortest at the spital shape due to its larger useless space. Inductance component of SFCLs with the spiral shape was around two times as high as those of other two shapes. This is not desirable since impedance characteristics of existing power systems can be changed. Resistance rise of current limiting elements was low at a spiral shape before the whole quench completion, which may act as a disadvantage for simultaneous quench in serial connection between current limiting elements, but the temperature tended to have similar values at higher voltages. On the other hand, hi-spital shape was severe at insulation level between current limiting lines. When these aspects were considered, we concluded that a meander shape was appropriate to design for a resistive SFCL based on thin films except the concentration of electric field at edge areas of strip lines.