• 한국초전도ㆍ저온공학회논문지
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• 제7권1호
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• pp.37-41
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• 2005

This paper describes the construction scheme of new distribution system using HTS(High Temperature Superconducting) power equipments such as cable, transformer and FCL(fault current limiter). At present, one of the most serious problems in distribution power system, especially for metropolitan complex city, is to obtain the ROW for cable line routes, space for downtown substations and satisfy the environmental protection caused by NIMBY phenomena. Unfortunately, it is expected that this situation will get more and more worse. As the HTS technology to apply in power system Is developed, HTS cable utilizing mass-capacity characteristic can be a useful countermeasure to overcome this problem. This paper describes the application methodology of 22.9kV HTS cable with low-voltage, mass-capacity characteristics replacing the 154kV conventional cable. By applying 22.9kV HTS cable, the HTS transformer with higher capacity for the reduction of space and transformer numbers of downtown substation is necessary. Also, if the leakage Impedance of HTS transformer is same as or lower than that of conventional transformer, the fault current of 22.9kV bus will increase because the HTS transformer capacity is larger than that of the conventional transformer. This means the parallel application of HTS-FCL to reduce the fault current in addition to the HTS cable and transformer can be necessary. With the basic construction scheme of new distribution system, this paper describes the future study points to realize this new distribution system using HTS equipments.

• 전기학회논문지
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• 제56권2호
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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.

• 조명전기설비학회논문지
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• 제23권12호
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• pp.90-95
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• 2009

배전계통에서 전력수요의 증가와 분산전원의 증가로 대용량 변압기의 적용이 불가피하게 되었다. 하지만, 대용량 변압기로 교체할 경우 배전계통에 고장발생시 고장전류의 크기가 증가되어 기존에 설치된 차단기 및 보호기기의 차단용량 초과로 인해 교체에 따른 경제적 비용 상승이 우려된다. 따라서, 대용량 변압기의 교체시 고장전류 증가 문제를 해결하기 위한 방안 중 하나로 초전도한류기를 설치하는 방안을 검토하고 있다. 하지만, 초전도한류기는 도입위치에 따라 ��치 발생 시 초전도한류기의 저항 크기가 다르게 되며, 이로 인해 고장전류 제한효과가 다르게 되며 기존의 보호 장치들의 동작에 영향을 주게 된다. 본 논문에서는 모의 배전계통에 초전도한류기를 적용하였을 경우 도입위치에 따라 전류제한효과를 포함하여, 모선 전압강하, 고장제거에 따른 초전도한류기의 회복특성을 실험을 통해 비교 분석하였다.

• 대한전기학회논문지:전력기술부문A
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• 제55권8호
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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.

• 한국초전도ㆍ저온공학회논문지
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• 제10권2호
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• pp.34-37
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• 2008

According to the recent design of an HTS (High Temperature Superconducting) power transformer whose capacity is hundreds MVA, the rated current values of the low voltage side are generally over thousands amps. Considering the performance of the recent HTS wires, it is inevitable to use several HTS wires in parallel for large rated current. Lots of stacked HTS wires were fabricated and tested so far, and the results have showed that we have to transpose each wire in order to reduce the AC losses as well as to increase the current capacity. But many development programs about HTS transformers reveal that the transposition of the several wires during the winding process is quite difficult not only in case of the layer windings but also in case of the pancake type ones. So, we need transposed multiple HTS wire which we can handle like single wire or cable for the HTS windings of large capacity power transformer. We fabricated several kinds of samples of multiple HTS wire with transposition to apply it to the HTS windings of power transformer. The electrical characteristics such as critical currents or AC losses are analyzed by experiments in case by case. Finally we present the best design of a multiple HTS wire for power transformer.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2005년도 제36회 하계학술대회 논문집 B
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• pp.1234-1236
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• 2005

High temperature superconducting(HTS) windings for an HTS transformer which have been developed have two kinds of type, one is the layer type and the other is disk type. The disk type windings have advantages over the layer type ones for a power transformer such as good insulation and limit of voltage stress. But this kind of HTS winding generates excessive AC losses caused by strong magnetic field component perpendicular to the surface of the HTS wire. Nevertheless, the layer type windings have adopted for an HTS power transformer so far because of the small AC losses of the HTS windings. 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 type HTS winding. This new type of HTS winding consists of pile of lots of HTS disk windings which have no resistive joint between them. A prototype of an HTS winding was fabricated by the new winding method we proposed and characteristic test was carried out. The test result shows that the new type HTS windings can be applied to HTS power transformers, especially to the high voltage ones.

• KIEE International Transaction on Electrical Machinery and Energy Conversion Systems
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• 제4B권2호
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• pp.54-58
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• 2004

This paper presents the iron core design method of a high temperature superconducting (HTS) transformer considering voltages per turn (V/T). In this research, solenoid type HTS coils were selected for low voltage (LV) winding and double pancake coils for high voltage (HV) winding, just as in conventional large power transformers. V/T is one of the most fundamental elements used in designing transformers, as it decides the core cross sectional area and the number of primary and secondary winding turns. By controlling the V/T, the core dimension and core loss can be changed diversely. The leakage flux is another serious consideration in core design. The magnetic field perpendicular to the HTS wire causes its critical current to fall rapidly as the magnitude of the field increases slowly. Therefore in the design of iron core as well as superconducting windings, contemplation of leakage flux should be preceded. In this paper, the relationship between the V/T and core loss was observed and also, through computational calculations, the leakage magnetic fields perpendicular to the windings were found and their critical current decrement effects were considered in relation to the core design. The ％ impedance was calculated by way of the numerical method. Finally, various models were suggested.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2006년도 하계학술대회 논문집 Vol.7
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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.

• 한국초전도ㆍ저온공학회논문지
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• 제5권3호
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• pp.30-33
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• 2003

1MVA high temperature superconducting (HTS) transformer with double pancake windings made of BSCCO-2223 HTS tapes was designed and manufactured. And prototype transformer with the same capacity was manufactured also. The each rated voltage of the HTS transformer is 22.9 kV and 6.6 kV. Four parallel BSCCO-2223 HTS tapes were wound in the double pancake windings of low voltage side. In order to distribute the currents equally in each HTS tapes, the three times transposition was performed between the double pancake windings. The windings of prototype transformer were wound using copper tape with the same size as BSCCO-2223 HTS tape. The core of the transformer was designed and manufactured as a shell type core made of laminated silicon steel plate. The several characteristics tests for the prototype transformer were performed in liquid nitrogen and insulation tests were accomplished also.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2001년도 추계학술대회 논문집 전기기기 및 에너지변환시스템부문
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• pp.24-26
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• 2001

The high temperature super-conductor transformer gains interests from the industries. This paper described construction and test results of a 10kVA HTS transformer. Three phase transformer with double pancake windings were constructed. BSCCO-2223 wire, silicon sheet steel core and FRP cryostats were used in that transformer After the test of basic properties of the 3 phase HTS transformer using no load test, short ciucuit test and full load test, continuous operation of 100 hours with pure resistive load has been carried out. Test proved over-load capability and reliability of the HTS transformer.