• The Transactions of The Korean Institute of Electrical Engineers
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• v.62 no.9
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• pp.1313-1317
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• 2013

With increasing demand of power, the equipment of power system is enlarging and the absolute capacity is going up. As a result, when a fault occurs, the fault current is consistently increasing. Therefore, I suggested some solution for limiting the fault current more efficiently. This study shows the characteristics of superconducting limiting elements and normal conducting elements combined with a transformer. We performed a short-circuit test about the fault current by using SCR switching control system operated from a CT. When short circuit accidents happened in the secondary side of a transformer, fault currents flowed and a SCR switching control system was operated. It resulted in a decrease of the fault current in the limited elements of third winding connected in parallel. For this test, we used YBCO thin films and normal conducting elements as the limited elements. Within a cycle, a superconducting fault current limiter with YBCO thin films reduced more than 90% of fault current because the resistance of superconducting elements sustainedly grew. On the other hand, the limiter with normal conductors limited as much as a set value because its resistance characteristic was linear. Consequently, in case of the limiter with superconductor, limiting range of the circuit was wide but the range of protective detection was undefined. In contrast, as for the limiter with normal conductors, limiting range and protection duty were appropriate.

• Progress in Superconductivity
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• v.5 no.2
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• pp.128-131
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• 2004

The resistive superconducting fault current limiters (SFCLs) are very attractive devices for the electric power network. But they have some serious problems when the YBCO thin films were used for the current limiting materials due to the in homogeneities caused by manufacturing process. When the YBCO films have some inhomogeneities, simultaneous quenches are difficult to achieve when the fault current limiting units are connected in series for increasing operating voltage ratings. Magnetic field application is one of the prospective way of inducing simultaneous quenches far the series-connected resistive FCL components. Magnetic field was typically generated by the fault current thorough a coil, which is connected to components of the fault current limiter in series, leaving the problem, which provides significant inductance to the power line and suppresses critical current density of the superconducting components. In this article we investigated the possible application of the protective current transformer (p-CT), which is available current source to the magnetic coil. This system inductively coupled to the circuit, therefore, remarkably reducing impedance to the circuit. The current by the protective current transformer was directly fed to the coil, generating magnetic field large enough to reduce critical current density of the components. This successfully induced simultaneous quenches of the series-connected resistive FCL components.

• Proceedings of the Korea Institute of Applied Superconductivity and Cryogenics Conference
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• 2002.02a
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• pp.229-232
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• 2002

In this paper, we investigated the cost comparison between a 30 MVA high temperature superconducting(HTS) transformer and a conventional large power transformer, and estimated a break even point in time of the HTS transformer comparing to the conventional large power transformer. A value between 5, 000 and 8, 500 kA-m is chosen to calculate the price of HTS tape in a 30 MVA HTS transformer. And the number of cryocooler is decided by estimating the generated energy loss in HTS transformer.

• Transactions on Electrical and Electronic Materials
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• v.18 no.1
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• pp.42-45
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• 2017

In this paper, a transformer type SFCL (superconducting fault current limiter) using an additional magnetically coupled circuit was suggested. Its transient fault current limiting characteristics, due to the winding direction of additional coupled circuit, were analyzed through fault current limiting tests. The suggested transformer type SFCL was composed of the primary winding, and one secondary winding wound on the same iron core together with an additional magnetically coupled circuit. That circuit consists of the other secondary winding together with the other SC (superconducting) element connected in parallel with its other secondary winding. As one of the effective design parameters to affect the transient fault current of the SFCL, the fault current limiting tests of the suggested SFCL were carried out considering the winding direction of its additional coupled circuit. It was confirmed that, through the analysis on the fault current tests of the SFCL, the quench sequence of two SC elements comprising the suggested SFCL could be adjusted by the winding direction of the additional coupled circuit.

• Proceedings of the KIEE Conference
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• 1999.07a
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• pp.247-249
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• 1999

This paper presents the design of a small scale High Tc superconducting power transformer. In the design of the transformer, BSCCO-2223 tape was considered as the conductor. Double pan cake winding was adopted in order to easy the construction of the winding and to lessen the leakage reactance of the transformer. Numerical calculation was used to decide the arrangement of the double pan cake winding. Estimation of the AC loss, magnetizing loss and self field loss, in the superconducting winding and the iron loss in the core were given.

• Proceedings of the KIEE Conference
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• 2000.07b
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• pp.934-936
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• 2000

This paper presents the design of a double pancake winding type high $T_c$ superconducting power transformer In the design of the transformer. BSCCO-2223 tape was considered as the conductor. Double pan cake winding was adopted in order to easy the construction of the winding and to lessen the leakage reactance of the transformer. Numerical calculation was used to decide the arrangement of the double pan cake winding. Room temperature bore type cryostat has been constructed and its heat loss was estimation.

• 한국초전도학회:학술대회논문집
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• 2009.07a
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• pp.114-114
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• 2009

• Proceedings of the KIEE Conference
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• 2005.07b
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• pp.1216-1218
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• 2005

A high temperature superconducting power transformer gets its advantages over the conventional ones when the rated capacity of the HTS transformer becomes 30 MVA or more. The standard capacity of the recent 154 kV/ 22.9 kV power transformer is 3 phase 60 MVA in Korea which means that the rated current of the secondary becomes more than 1,500 amps. Considering the current capacities of the HTS wires being developed recently, it is inevitable to use the HTS wires in parallel in order to be applied to the power transformer. But nonuniform distribution of currents and large AC losses are major problems in parallel HTS windings setting aside the difficulties of making parallel windings. To solve these problems, several kinds of multiply laminated HTS wires were fabricated and tested for the application of these multiple wire to an HTS power transformer. Test results were compared with that of each other and the best were selected for the application to an HTS power transformer.

• Proceedings of the KIEE Conference
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• 2004.11b
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• pp.176-178
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• 2004

HTS (High Temperature Superconducting) Transformer has the several useful characteristics in the viewpoints of technical and economical. Especially, an HTS transformer replaces the copper wire coils in a conventional transformer with lower loss HTS wire In addition, inexpensive, environmentally benign liquid nitrogen replaces the conventional oil as the electrical insulation (dielectric) and provides the necessary cooling for the HTS transformer Therefore, the Life-cycle cost of an HTS transformer is much more attractive than conventional because it is more energy efficient, lighter in weight, smaller in size, and environmentally compliant. HTS transformer can be the best way to replace with conventional transformer in the future. In this paper, we investigate the expected price of HTS transformer to have a merit in viewpoint of economic aspect. First, life-cycle cost of conventional transformer is calculated and based on this, the expected price of HTS transformer is evaluated, which HTS transformer is competitive against conventional transformer.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.67 no.4
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• pp.595-599
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• 2018

Interruption system with the transformer type superconducting fault current limiter(TSFCL) is proposed in this paper. The interruption system with a TSFCL is a technology that it maximizes the interruption function of a mechanical DC circuit breaker using a transformer and a superconducting fault current limiter. By a TSFCL, the system limits the fault current till the breakable current range in the fault state. Therefore, the fault current could be cut off by a mechanical DC circuit breaker. The Interruption system with a TSFCL were designed using PSCAD/EMTDC. In addition, the Interruption system with a TSFCL was applied to the DC test circuit to analyze characteristics of a current-limiting and a interruption operation. The simulation results showed that the Interruption system with a TSFCL interrupted the fault current in a stable when a fault occurred. Also, The current-limiting rate of the Interruption system with a TSFCL was approximately 69.55%, and the interruption time was less than 8 ms.