• The Journal of the Korea institute of electronic communication sciences
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• v.17 no.2
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• pp.279-290
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• 2022

A superconducting fault current limiter(SFCL) is a power device that exploits superconducting transition to control currents and enhances the flexibility, stability and reliability of the power system within a few milliseconds. With a high phase transition speed, high critical current densities and little AC loss, high-temperature superconducting (HTS) wires are suitable for a resistive-type SFCL. However, HTS wires due to the lack of optimization research are rather inefficient to directly apply to a fault current limiter in terms of the design and capacity, for the existing method relied the characteristics. Therefore, in order to develop a suitable wire for an SFCL, it is necessary to enhance critical current uniformity, select optimal stabilizer materials and conducted research on the development of uniform stabilizer layering technology. The high temperature superconducting wires manufactured by this study get an average critical current of 804 A/12mm-width at the length of 710m; therefore, conducted research was able to secure economic performance by improving efficiency, reducing costs, and reducing size.

• Progress in Superconductivity and Cryogenics
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• v.18 no.1
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• pp.37-40
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• 2016

We have investigated the addition effect of NiO magnetic nanoparticles on crystal structure, microstructure as well as superconducting properties of $MgB_2$. NiO-added $MgB_2$ samples were prepared by the solid-state reaction method. The superconducting transition temperature ($T_c$) of 37.91 K was obtained for pure $MgB_2$, and $T_c$ was found to decrease systematically on increasing the addition level of NiO. X-ray diffraction (XRD) analysis revealed that no substitution of Ni for Mg in the lattice of $MgB_2$ was occurred. The microstructural analysis shows that the pure $MgB_2$ sample consists of plate shape $MgB_2$ grains, and the grains get refined to smaller size with the addition of NiO nanoparticles. At 5 K, high values of critical current density ($J_c$) were obtained for small amount NiO-added $MgB_2$ samples as compared to pure sample. The enhancement in $J_c$ could be attributed to the refinement of $MgB_2$ grains which leads to high density of grain boundaries in NiO-added $MgB_2$ samples.

• Journal of the Korean institute of surface engineering
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• v.29 no.5
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• pp.430-436
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• 1996

We have grown superconducting thin films on various substrates using a pulsed laser deposition (PLD) method. $YBa_2Cu_3O_7-\delta$ (YBCO) superconducting thin films with the superconducting transition temperature ($T_{c. offset}$) of 87K were grown on Si substrates using yittria-stabilized zirconia (YSZ) and $CeO_2$ double buffer layers. We have developed a large area pulsed laser deposition system. The system was designed to deposit up to 6 different materials on a large area substrate up to 7.5cm in diameter without breaking a vacuum. The preliminary runs of the deposition of YBCO superconducting thin films on $SrTiO_3$ substrate using this system showed a very uniform thickness profile over the entire substrate holder area. $T_{c}$ of the deposited YBCO thin film, however, was scattered depending on the position and the highest value was 85K.

• 한국초전도학회:학술대회논문집
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• v.10
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• pp.22-22
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• 2000

The discoveries of high temperature superconductors received great attention due to their high critical temperatures. These materials also exhibit extremely high critical magnetic fields and high critical current density at low temperature, high magnetic field. Thus, they are the most promising materials for superconducting magnets above 20 T. In this talk, progress in the development of HTS materials and insert coils at the National High Magnetic Field Laboratory will be reviewed. In 1999, a Bi-2212 stack of double pancakes generated 3 T in a 19 T background field. These results will be reviewed in terms of implications for future systems. Individual double pancakes of Bi-2223 have also been tested and their performance will also be discused. The present goal of a 57 system will be presented and the key technical requirements for larger, higher field systems will be addressed. It will be shown that in addition to increased critical current density, improved mechanical performance (stain resistanced) is necessary for high field systems. Furthemore, improvements in the conductor n-value will improve prospects for operational systems.

• Transactions on Electrical and Electronic Materials
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• v.6 no.4
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• pp.186-189
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• 2005

We have fabricated superconducting HTSC ceramic thick films by chemical process. c-axis oriented HTSC thick films have been attempted bi-axially textured Ni tapes. The x-ray diffraction pattern of the HTSC thick films contained superconducting phase crystal. The critical temperature and critical current density was 110K.

• Transactions on Electrical and Electronic Materials
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• v.5 no.3
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• pp.120-121
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• 2004

YBaCuO thick films were fabricated by plasma enhanced chemical vapor deposition, and the crystallinity and the superconducting properties were investigated. The growth temperature to obtain the thick films was decreased by around 150$^{\circ}C$ due to plasma enhancement. The zero resistivity temperatures for films grown at 590$^{\circ}C$ and 620$^{\circ}C$ were 55 and 80 K, respectively.

• Progress in Superconductivity and Cryogenics
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• v.9 no.2
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• pp.27-30
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• 2007

The electrical insulation design and withstanding test of mini-model coils for 600 kJ class conduction cooled high temperature superconducting magnetic energy storage (HTS SMES) have been studied in this paper. The high voltage is generated to both ends of magnet of HTS SMES by quench or energy discharge. Therefore, the insulation design of the high voltage needs for commercialization, stability, reliability and so on. In this study, we analyzed the insulation composition of a HTS SMES, and investigated about the insulation characteristics of the materials such as Kapton, AIN and vacuum in cryogenic temperature. Base on these results, the insulation design for 600 kJ conduction cooled HTS SMES was performed. The mini-model was manufactured by the insulation design, and the insulation test was carried out using the mini-model.

• Progress in Superconductivity and Cryogenics
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• v.15 no.2
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• pp.44-47
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• 2013

Large AC loss from the second generation (2G) high temperature superconducting (HTS) wires has been one of the major bottlenecks in power applications with HTS materials. Moreover, the large power applications also require the large current capacity from the HTS wires, which makes them produce larger AC losses. In order to reduce the AC loss from the HTS conductors with large current capacity, an HTS compact cable with some striations on the superconducting layers has been proposed. In this paper, we prepared some sample HTS compact conductors with striations, and measured their magnetization loss from the external magnetic field. We also made some slits on the superconducting layer of the HTS wire by laser cutting to reduce the aspect ratio of the superconducting layers. It would make the low eddy current loss and magnetic decoupling. Finally, the magnetization losses of the sample HTS compact conductors were measured and analyzed.

• Proceedings of the Materials Research Society of Korea Conference
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• 1992.05a
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• pp.17-17
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• 1992

The ceramic high transition temperature superconducting materials present many interesting characteristics that will be analysed from two points of view: physical behavior, and chemical aspects. From the first point of view, these materials display an enormous variety of different physical properties. At low doping levels the normal state shows antiferromagnetism and insulating behavior. At intermediate doping levels, an anomalous metallic state appears and, the optimum Tc in the superconducting state is generated. With increasing doping a normal metallic state develops and superconductivity starts to disappear. Many of the physical phenomena that describe the overall behavior when doping levels are changed will be discussed. From the poing of view of the chemical aspects. we well discuss some of the problems involved in the methods of preparation with particular emphasis on defects, crystal structures, critical currrents, and applications in technology.

• Progress in Superconductivity and Cryogenics
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• v.7 no.1
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• pp.42-46
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• 2005

The resistive type high temperature superconducting fault current limiter (HTSFCL) limits the fault current using the resistance generated by fault current. The generated resistance by fault current makes large pulse power which makes the operation of HTSFCL unstable. So, the cryogenic cooling system of the resistive type HTSFCL must diffuse and eliminate the pulse energy very quickly. Although the best way is to make wide direct contact area between HTS winding and coolant as much as possible, HTS winding also needs the impregnation layer which fixes and protects it from electromagnetic force. This paper deals with the thermal conductivity and dielectric strength of some epoxy compounds for the impregnation of high temperature superconducting (HTS) winding in liquid nitrogen. The measured data can be used in the optimal design of impregnation for HTS winding. Aluminar filling increased the thermal conductivity of epoxy compounds. Hardener also affected the thermal and electric characteristic of epoxy compounds.