• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2006.06a
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• pp.204-205
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• 2006

In the response to the demand for electrical energy, much effort aimed to develop and commercialize high temperature superconducting (HTS) power equipments has been made around the world. In Korea, companies and universities are developing a power distribution and transmission class HTS transformer that is one of the 21st century superconducting frontier projects. The composite winding of transmission class HTS transformer is concentrically arranged H1-L-H2 from center. H1 is continuous disk type, L is layer type and H3 is continuous disk type. For the development of transmission HTS transformer with composite winding, the cryogenic insulation technology should be established. We have been analyzed insulation composition and investigated electrical characteristics such as breakdown of $LN_2$, barrier, kapton films, surface flashover on FRP in $LN_2$. We are going to compare with measured each value and apply the value to most suitable insulating design of the HTS transformer.

• Proceedings of the KIEE Conference
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• 1996.07a
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• pp.160-162
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• 1996

The estimation of AC losses is demanded for higher efficiency and stability in AC use of superconducting coils. Hysteresis loss occurred by a.c. transport current is called of self field loss, and it is major part of losses generated in a.c. superconducting wire in case of located in low external magnetic field as superconducting transformer with iron core, or in short twist pitch wire, multiply stacking cable. In this paper, we calculate self field loss of superconducting wire.

• 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.

• Journal of Electrical Engineering and Technology
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• v.7 no.5
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• pp.659-663
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• 2012

The application of large power transformer into a power distribution system was inevitable due to the increase of power demand and distributed generation. However, the decrease of the power transformer's impedance caused the short-circuit current of the power distribution system to be increase thus, the higher short-circuit current exceeded the cut-off ratings of the protective devices such as circuit breaker. To solve these problems, several countermeasures have been proposed to protect the power system effectively from higher fault current and the superconducting fault current limiter (SFCL) has been expected to be the promising countermeasure. In spite of excellent current limiting performances of the SFCL, on the other hand, the efforts to apply the SFCL into power system has been delayed due to both the limited spaces for the SFCL's installation and its long recovery time after the fault removal. In order to solve these problems, a hybrid SFCL, which can perform either first half cycle limiting of first half cycle non-limiting operation, has been developed by corporation of LSIS (LS Industrial System) and KEPCO (Korea Electric Power Corporation). In this paper, we tried to requirements hybrid SFCL by PSCAD/EMTDC. Simulation results of our analysis of the hybrid SFCL is that its accompanied the characteristics both the limit the fault current and quick recovery caused by the less impact from superconductor.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2009.11a
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• pp.215-215
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• 2009

Improved flux-lock type superconducting fault current limiter(SFCL) is composed of a series transformer and superconducting unit of the YBCO coated conductor. The primary and secondary coils in the transformer were wound in series each other through an iron core and the YBCO coated conductor was connected with secondary coil in parallel. In this paper, we investigated the current limiting characteristics through initial line current after fault initiation. through the analysis, it was shown that the smaller initial line current is superior to current limiting characteristics and a point of view of power burden of the YBCO coated conductor.

• Proceedings of the KIEE Conference
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• 2008.11a
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• pp.37-39
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• 2008

This paper suggests a decision scheme for optimal insertion resistance in an Superconducting Fault Current Limiter (SFCL) application to reduce the transformer inrush current. This scheme and the SFCL model are implemented using Electromagnetic Transient Program (EMTP). We determine the optimal SFCL resistance by EMTP simulation, and this value is applied to model the SFCL by EMTP. The simulation results show the validity and effectiveness of the suggested scheme and the ability of a SFCL to reduce the inrush current.

• The Transactions of the Korean Institute of Electrical Engineers A
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• v.54 no.5
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• pp.212-216
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• 2005

This paper describes the application scheme of resistive HTS-FCL(High Temperature Superconducting-Fault Current Limiter) on future new distribution system. Future new distribution system means the power system to which applies the 22.9kV HTS cable with low-voltage and mass-capacity characteristics replacing the 154kv conventional cable in addition to HTS transformer and HTS-FCL. The fault current of future new distribution system will increase greatly because of the inherent characteristics of HTS transformer/cable and applications of distributed generations and spot networks and so on. This means that the HTS-FCL is necessary to reduce the fault current below the breaking capacity. This paper studies the appropriate location, parameters and the influences of HTS-FCL on future new distribution system. Finally, this paper suggests the reasonable basic parameters of resistive HTS-FCL for future KEPCO new distribution system.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.56 no.2
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• pp.295-300
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• 2007

High temperature superconducting (HTS) windings for an HTS transformer which have been developed have two kinds of type, one is the layer winding and the other is disk winding. The layer winding has adopted for an HTS power transformer so far because of the small AC losses of the HTS windings. The disk windings have surface of the HTS wire. We propose a new winding method for a high voltage HTS transformer which has advantages of both type of HTS windings, and we call it continuous disk winding. This new HTS winding consists of pile of HTS disk windings. The continuous disk winding was fabricated with multi-stacked HTS wires for dover HTS transformer. We can check the potential possibility from the characteristic test of the fabricated winding. The new type HTS windings can be applied to HTS power transformers, especially to the high voltage ones.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.63 no.3
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• pp.414-417
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• 2014

At present, the demand for electric power increases, the electric power system is complicated. The size of the line-to-ground fault and the line-to-line fault occurred with complication of electric power system continue to increase, therefore several issues are raised. To address these issues effectively, the superconducting fault current limiter (SFCL) has been proposed, this study is ongoing. In this paper, we applied the SFCL in three-phase transformer and comparative analysis of the electric power burden to the SFCL. The superconductor is combined to the third winding of transformers in connection structure. In case of a third line-to-line fault, we did comparative analysis of the electric power burden to the SFCL based on the turn ratio of transformer third winding. In this case, we could confirm as the third turn ratio increased, electric power impressed to the superconducting element increased.