• Journal of Electrical Engineering and Technology
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• 제11권3호
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• pp.543-550
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• 2016

The Active Superconducting Current Controller (ASCC) is a new type of Superconducting Fault Current Limiters (SFCL) which can limit the fault current in different modes. It also has the particular abilities of compensating active and reactive powers for electrical networks. In this paper, it is confirmed that the performance of ASCC in different operating modes introduces a limiting impedance in series with the network which can even degrade the transient stability and the operation of the Over-Current Relays (OCR) employed in a power system. In addition, the model of a three-phase ASCC is simulated, and the effect of descriptive modes on the current limiting level is investigated. For the transient stability analysis, a single machine-infinite bus system is tested, and the effect of operation modes is studied based on an equal area criterion obtaining the critical time and the critical angle. Modifying the setting parameters of OCR such as time dial and pick-up current, the protective coordination is also studied in different operating modes.

• 한국초전도ㆍ저온공학회논문지
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• 제10권2호
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• pp.30-33
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• 2008

Several kinds of superconducting fault current limiters (SFCLs), which reduces huge fault current, have been developing by many research groups. The SFCL has no impedance during normal operation, so it dose not give any influence to electric power system. The resistive type SFCL reduces the fault current with the impedance generated in the superconducting part of the SFCL when the fault current exceeds the critical current of SFCL. In this paper, a new type resistive SFCL made of bifilar coil wound with two different high-Tc superconducting (HTS) wires in parallel. Although a bifilar coil has theoretically no inductance, the bifilar coil made in this paper could generate inductance at fault. The specifications of the used two wires were considerably different, thus current distribution between the two HTS wire was different at fault. When the fault current exceeded the critical current of one wire in the bifilar coil, the momentary sharp increase of impedance was detected. Base on the results, a new resistive type SFCL can generate not only resistance but also inductance, which can be used to control a fault current in the future.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2005년도 추계학술대회 논문집 전력기술부문
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• pp.344-346
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• 2005

The recovery time of developing SFCL(Superconducting Fault Current Limiter) has an uncertainty. In general, the recovery time is estimated at 1 sec and more, even though the progress of SFCL technology is considered. However, auto reclosing time of circuit breaker is 0.5 sec in Korean distribution power system. It is impossible to apply only one SFCL to power system because the recovery time is over the reclosing time of protection system. This study proposes a new SFCL system for distribution power system application. The proposed systems consider auto reclosing action for the protection in practical power system and consist of tow parallel SFCLs.

• 한국초전도학회:학술대회논문집
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• 한국초전도학회 1999년도 High Temperature Superconductivity Vol.IX
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• pp.384-387
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• 1999

A new multi-seeding process for the growth of YBa$_2Cu_3O_x$ single crystals was developed. This process introduces an additional heating step to peritectic temperature and a subsequent slow cooling step to the growth temperature following the point when the crystals contacted. The crystal growth was resumed thereafter. The results obtained with this new process were compared with those of the conventional growth process, in which materials were only kept at the growth temperature. There was significant improvement in trapped magnetic field over the conventional multi-seeding process, which is believed to be due to complete elimination of liquid phase between crystals.

• 대한전기학회논문지:전력기술부문A
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• 제50권6호
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• pp.293-299
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• 2001

This paper proposes a new power conditioning system for the SMES composed of a thyristor PWM converter with a resonant commutation circuit. The operation of the proposed system and the dynamic interaction between SMES and the power system is analyzed by a theoretical approach with equivalent circuits and verified by computer simulations with EMTP, considering a typical 154kV power system. The proposed system can provide a solution for the power factor regulation and harmonic level reduction in the ac terminal with low-cost system configuration.

• 대한전기학회논문지:전력기술부문A
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• 제54권12호
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• pp.580-585
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• 2005

The recovery time of developing SFCL(Superconducting Fault Current Limiter) has an uncertainty. In general, the recovery time is estimated at 1 sec and more, even though the progress of SFCL technology is considered. However, auto reclosing time of circuit breaker is 0.3 or 0.5 sec in Korean power system. It is impossible to apply only one SFCL to power system because the recovery time is over the reclosing time of protection system. This study proposes two new SFCL systems for power system application. The proposed systems consider auto reclosing action for the protection in practical power system and consist of tow parallel SFCLs.

• 한국초전도ㆍ저온공학회논문지
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• 제7권1호
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• pp.51-56
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• 2005

The recovery time of developing SFCL(Superconducting Fault Current Limiter) has an uncertainty. In general, the recovery time is estimated at 1 sec and more, even though the Process of SFCL technology is considered. However, auto reclosing time of circuit breaker is 0.3 sec in Korean power system. It is impossible to apply only one SFCL to power system because the recovery time is over the reclosing time of protection system. This study proposes two new SFCL systems for power system application. The proposed systems consider auto reclosing action for the protection in practical power system and consist of tow parallel SFCLS.

• 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.

• 한국초전도ㆍ저온공학회논문지
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• 제5권2호
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• pp.20-29
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• 2003

As power systems grow more complex and power demands increase, the need of underground transmission system is increasing gradually. But it is very difficult and high in cost to construct new ducts and/or tunnels for power cables in metropolitan areas. HTS (High Temperature Superconducting) cable can carry very high current densities with strongly reduced conductor loss and allow high power transmission at reduced voltage. Therefore HTS cable can transfer more power to be moved in existing ducts, which means very large economical and environmental benefits. A development project for a 22kV class HTS cable is ongoing at a research centers, and the cable manufacturer in Korea. In this paper, we carried out investigation for application of 22kV class HTS cable in Korean utility networks. The results show that the HTS cable is applicable to replace IPB in pumping-up power plant, withdrawal line in distributed generation, withdrawal line in complex power plant, and conventional under ground cable. Finally, as the cost of HTS wire and refrigeration drops, the technical and economical potential of HTS cable is evaluated positively.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2005년도 제36회 하계학술대회 논문집 A
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• pp.66-68
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• 2005

In Korea power system, the transfer capability of transmission line is limited by the voltage stability and it is difficult to construct new iron tower due to incremental interest for environmental problem and construction costs. Recently, HTS cable could be one of the countermeasures to solve the transfer limit because of it is transported to large power with compact size However, the characteristic of HTS cable have a various problem. This paper presents the effects of congestion cost reduction by the application of HTS (High-Temperature Superconducting) cable. In this paper, the transmission ability before and after application of HTS cable are examined in a viewpoint for voltage stability. therefore, the effects of congestion cost reduction by HTS cable.