• The Transactions of The Korean Institute of Electrical Engineers
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• v.61 no.12
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• pp.1944-1947
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• 2012

In this work, we investigated quench characteristics of matrix-type superconducting fault current limiters (MFCLs) according to the turn number of reactors. The reactors used in MFCLs apply magnetic field to superconducting elements within reactors when fault currents surge into MFCL systems. It makes the fast and simultaneous quenches between superconducting elements. Also reactors decrease the fault power burden of superconducting elements by bypassing the partial fault currents to itself, when quench occurs. These structure proposed in this work can be expected to achieve much more current limiting capacity even though it uses less superconductors compared with other type SFCLs. Three reactors were made by Bakelite. These reactors with the turn number of 190, 380 and 570, had the length of 270 mm and diameter of 80 mm. We reported experimental results, including fault currents, fault voltages and resistance in superconducting elements according to the turn number of reactors. We confirmed that experimental results will be useful in next future plan for the real power grid.

• Progress in Superconductivity and Cryogenics
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• v.5 no.1
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• pp.60-65
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• 2003

An effective modeling and simulation scheme of a resistive type Superconducting fault Current Limiter (SFCL) using PSCAD/EMTDC is proposed in this paper. In case of High Temperature Superconducting (HTS) resistive type fault current limiter current limiting is implemented by the ultra-fast transition characteristics from the superconducting (non-resistive) state to the normal (resistive) state by overstepping the critical current density. The states can generally be divided into three sub-states: the superconducting state the quench state and the recovery state respectively. In order to provide alternative application schemes of a resistive type SFCL, an effective modeling and simulation method of the SFCL is necessary. For that purpose, in this study, an actual experiment based component model is developed and applied for the simulation of the real resistive type SFCL using PSCAD/EMTDC. The proposed simulation scheme can be implemented to the grid system readily under various system conditions including sort of faults and the system capacity as well. The simulation results demonstrate the effectiveness of the proposed model and simulation scheme.

• 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.

• Proceedings of the KIEE Conference
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• 2001.07b
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• pp.865-867
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• 2001

Generally large synchronous rotating machines with 2 poles have more merits than the others with more than 2 poles Superconducting synchronous rotating machines also have the same tendency, but they have different structure from conventional ones because of no magnetic core inside of the rotor. As the result, design approaches of the superconducting field coils are also different, which would be classified into 2 types according to their coil shapes. The first one is race-track type and the other is saddle type Race-track type machines have almost the same structure with conventional salient pole generators which are being used as largely small scale machines with more than 2 poles. On the other hand saddle type machines correspond to conventional cylindrical generators with 2 poles used for large turbine system in power plants. In this paper several types of superconducting field coils are introduced for 2 pole superconducting machine design and then the feasibility of each type is considered. Moreover, based on the consideration. 1MVA superconducting generator(S.G.) with saddle type field coil is designed electromagnetically.

• Progress in Superconductivity and Cryogenics
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• v.12 no.1
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• pp.32-36
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• 2010

Superconducting current leads are indispensible for reducing power loss when subjecting current into superconducting magnets. HTS(High-Tc superconducting) current leads are divided into two types; one is bulk type and the other is tape type. In this paper, conceptual design on the HTS current leads which adopts tape type for nuclear fusion magnets is carried out using magnetic field analysis and thermal analysis. When large current flows through superconducting current leads, strong self magnetic field is generated and applied to the superconducting tapes. This phenomenon leads to the critical current decrease of the superconducting tape. Therefore, we analyzed magnetic field distribution of current leads and found the proper arrangement with respect to the various HTS tapes. In addition to the magnetic field analysis, heat leak through the current leads was also calculated to know which HTS tape is superior than others in thermal aspect. Magnetical field analysis and calculation of heat leak are performed to design 2 kA class HTS current leads.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.56 no.6
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• pp.993-999
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• 2007

This paper discusses the effects of CD type superconducting cable operation in 22.9kV multi neutral grounded distribution system during L-G fault and counterplans to power system protection. In case of using the 3-phase CD-type superconducting cable, the inductance of superconducting cable system would be decreased due to the current of shield part of superconducting cable, which is opposite direction and nearly equal value with respect to main superconductor. However, when the shield circuit system is operated in shorted state, shield current decreases faulted ground current and give effects to power system protection scheme. This study examines the phenomena of single line to ground fault case in above mentioned system using the EMTDC program and discusses the right operation method of superconducting shield.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.21 no.12
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• pp.1111-1117
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• 2008

A transformer type superconducting fault current limiter (SFCL) is one of the fault current limiters which have been proposed to reduce the fault current in the transmission lines. This paper proposes the new circuit configuration of a transformer type SFCL and also investigates the operating characteristics of the transformer type SFCL containig the resistor in the tertiary winding. The proposed SFCL contains the resistor in the tertiary winding. The newly inserted resistor can divert the power which the High-Tc superconducting has to bear. Because the resistor in the tertiary winding relieves the power of the High-Tc superconducting, it is possible that the proposed transformer type SFCL can decrease the more larger fault current than the conventional SFCL with the same High-Tc superconducting. And the cost of the proposed transformer type SFCL can be reduced.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.60 no.4
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• pp.880-884
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• 2011

The matrix-type superconducting fault current limiter (MSFCL) consists of the trigger and current-limiting parts. The trigger part with reactors connected in parallel improves the quenching characteristics by applying the external magnetic field into the superconducting units. The current-limiting part with superconducting units connected in parallel and shunt reactors connected in series limit the fault current when the fault occurs. We developed the integrated reactor with the trigger and the current-limiting parts to apply high external magnetic field into the superconducting units. This was composed of a superconducting unit for the trigger part and two superconducting units for the current-limiting parts. We confirmed that the external magnetic field generated in the MSFCL with an integrated reactor was larger than that of the MSFCL with the separated reactors. So the differences of voltages generated between superconducting units were decreased in the difference according to the increment of the applied voltage. The whole magnitude of the SFCL was reduced because the volume of an integrated reactor could be reduced by one-third than that of the separated reactors. We confirmed that the critical behavior between the superconducting units in the MSFCL with an integrated reactor was more improved than that of the MSFCL with the separated reactors.

• 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.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.19 no.4
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• pp.391-397
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• 2006

We present investigations of a hybrid type superconducting fault current limiter (SFCL), which consists of transformers and resistive superconducting elements. The secondary windings of the transformer were separated into several electrically isolated circuits and linked inductively with each other by mutual flux, each of which has a superconducting current limiting element of $YBa_2Cu_3O_7$ (YBCO) stripes as a current limiting element. Simple connection in series of the SFCL elements tends to produce ill-timed quenching because of power dissipation unbalance between SFCL elements. Both electrical isolation and mutual flux linkage of the elements provides a solution to power dissipation unbalance, inducing simultaneous quench and current redistribution of the YBCO films. This design enables to increase the voltage rating of SFCL with given YBCO stripes.