• The Transactions of The Korean Institute of Electrical Engineers
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• v.58 no.11
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• pp.2089-2094
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• 2009

The fault current has increased due to growth of distributed generations for the large power demand in power distribution system. To solve some problem such as excess of the circuit breaker's cut-off ratings, the superconducting fault current limiter(SFCL) has been progressed. However, the operational characteristics of the relay is changed by SFCL. Therefore, the proper impedance for the SFCL should be selected to keep protective coordination with the SFCL when SFCL is introduced on the neutral line of main transformer in distribution system. In this paper, the proper normal conducting resistance was suggested to solve the problem in case of the protection coordination with SFCL.

• Progress in Superconductivity
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• v.3 no.2
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• pp.241-246
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• 2002

We have performed the current and voltage loading tests of resistive superconducting fault current limiters (SFCLS) based on $YBa_2$$Cu_3$$O_{7}$(YBCO) films with the diameter of 2 inch. The SFCL consists of meander-type YBCO stripes covered with 200 nm Au layer grown in situ for current shunt and heat dispersion at hot spots. The minimum quench current of an SFCL unit was about 25 Apeak. Seven SFCL units were connected in parallel fur the current load ing tests at power source of 100 $V_{rms}$ $/2,000A_{rms}$. This SFCL units had maximum limiting current of 170 Apeak during the fault instant and then successfully controlled the fault current below 100 Apeak within 1~2 msec after short circuit. Increased short current also reduced the quench completion time with little change of current limiting characterization. We connected six SFCL units in series fur the voltage loading tests at power source of $1,200 V_{rms}$/170 $A_{rms}$ at this time. The shunt resistors were inserted into each SFCL unit to eliminate power imbalance originated from serial connection of SFCL units. Each SFCL unit was quenched simultaneously during the fault condition. The current increased up to 40 $A_{peak}$ and decreased to 14 $A_{peak}$ after 3 cycles. Quench was completed within 1 msec after the fault. We confirmed operating characteristics of 140 kVA($120 A_{rms}$ $\times$ 1,200 $V_{rms}$) SFCL and presented the manufacturing possibility of 3.3 kV SFCL using 4 inch YBCO films.BCO films.lms.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.28 no.12
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• pp.30-37
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• 2014

Recently, Concerns of imbalance for power supply has been raised by the increase of electric power consumption, but the interest of electric safety is still lacking due to the incompleteness of regulations. Particularly, Arcing fault, direct cause of electric fire accidents, is difficult to detect, interrupt due to unformal signal behaviour in previous research and apply to real system. In this paper, Arcing fault simulator device was fabricated to investigate the characteristics of series arcing fault and simulated the faults in various real load. Also, this study are analysed arcing fault signal by using the harmonic analysis of the acquired data from the current of the power supply and proposed the methods to prevent the series arcing fault accidents in advance.

• 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.

• Transactions on Electrical and Electronic Materials
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• v.8 no.5
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• pp.222-225
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• 2007

In this paper, we compared the current limiting characteristics of both the hybrid type and the flux-lock type superconducting fault current limiters(SFCLs), which have a magnetic coupling structure between a primary winding and several secondary windings. The limiting impedances of two SFCLs were derived from each equivalent circuit considering the design parameters of SFCL such as the self-inductance of secondary winding and the resistance of $high-T_C$ superconducting(HTSC) element. Through the comparison for the limiting impedances of two SFCLs considering the dependence of the HTSC element's resistance on the applying voltage into the SFCL, the hybrid type SFCL was confirmed to have larger limiting impedance with smaller resistance of HTSC element than the flux-lock type SFCL. It was expected from the analysis that the hybrid type SFCL was more advantageous than the flux-lock type SFCL from the viewpoint of the fault current limiting level.

• Journal of Electrical Engineering and Technology
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• v.12 no.2
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• pp.522-532
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• 2017

In this study, we propose a fault analysis method for a power distribution grid with PCS-based DERs. We first explain the characteristics of a PCS-based DER. According to the characteristics, the DER is considered as a current-controlled voltage source, which produces varying voltages within a certain limit so that currents equal to given references flowing from the DER to the grid (currents controlled). So, we introduce the symmetrical equivalent models in the form of varying voltage source for fault analysis and then, construct a convex optimization problem to solve the fault problem associated with the equivalent models and grid conditions. Thus, the proposed method enables to perform a proper fault analysis considering the characteristics of the DER, which are currents controlled, voltage limited, and unity power factor achievement. To verify the validity of the proposed method, we perform computer simulations with the proposed method and with MATLAB Simulink, and the results are compared.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.67 no.10
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• pp.1286-1291
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• 2018

In recent years, the proliferation of DER (distributed energy resources) is progressing rapidly. In particular, research on LVDC distribution grid with various advantages has begun. In order to commercialize this LVDC grid, direct current protection method should be established by analysis of DC faults. Recently, the development of HSCB (high-speed circuit breaker) for new ${\pm}750[V]$ LVDC grid has been researched. This paper deals with the calculation of the maximum short-circuit fault current of the HSCB as a part of the development of HSCB for the LVDC distribution grid. First, modeling using PSCAD was carried out for PV array with BESS on the Gochang Power Test Center system. Next, to calculate the rated capacity of HSCB, fault currents were calculated and the characteristics were analyzed through fault simulations. Thus, this study results can help to establish short-circuit capacity calculation of HSCB and protection plan for DC protection relay system.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.18 no.5
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• pp.140-145
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• 2004

In this paper, we analyzed the operational characteristics of the modified DC reactor type SFCL and derived the design condition of superconducting coil to be operated properly as power source as well as fault current limiter. It was confirmed through the simulation for the operation of this SFCL that the modified DC reactor type SFCL could be operated as both the uninterruptible power supply and the fault current limiter by controlling the duty ratio of GTO thyristor bridge.

• Proceedings of the Korea Institute of Applied Superconductivity and Cryogenics Conference
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• 2002.02a
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• pp.219-220
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• 2002

In this paper, we propose non-soldered current lead was introduced which has low contact resistivity for fault current limiters of YBCO film. Carbon/Cu has good thermal conductivity, electrical conductivity and chemically stable, and so forth. Therefore it seems to be suitable material of current lead for current limiters of YBCO film. We have investigated electric field-current in field of 0-130 mT and quench characteristics of a YBCO film. Experimental results show that characteristics of transport is all right using Carbon/Cu-current lead.

• Proceedings of the Korean Institute of IIIuminating and Electrical Installation Engineers Conference
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• 2008.05a
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• pp.332-334
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• 2008

The matrix-type superconducting fault current limiter (SFCL) using YBCO thin film consists of the trigger and current-limiting parts. We fabricated the matrix-type SFCL with the integrated current limiting modules. we carried out the experiment of matrix-type SFCL with the integrated current limiting modules connected in series or parallel. We saw current characteristics due to ratio of change the shunt resistance and turns. We confirmed that the difference of critical current between superconducting units was decreased by increment of current flowing into the reactor which applied the magnetic field into the superconducting units..