• Proceedings of the KIEE Conference
• /
• 1995.11a
• /
• pp.406-410
• /
• 1995

A superconducting cable is one of the promising methods of undground transmission of high electric power in the future. It is very important that composite insulation system of $LN_2$ and polymer films takes into consideration for application high $T_c$ superconductor. This study is about both the partial discharge and properties V-t in $LN_2$. As result, applied voltage doesn't depend on the radius of non-eroded area but eroded area. And eroded area is observed the formation such as the ring of a tree.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
• /
• v.29 no.2
• /
• pp.106-109
• /
• 2016

The YBaCuO superconducting bulks were prepared by the thermal diffusion process involving the peritectic reaction to investigate the effect on microstructure and superconductivity. All the diffused YBaCuO could be successively separated from superconducting 123 phase by applying the thermal diffusion process. Electromagnetic properties of treated and untreated YBaCuO superconductor were evaluated to investigate the pinning effect. It was confirmed experimentally that a large amount of magnetic flux was trapped in the thermal treated superconducting bulk than that in the untreated one, indicating that the pinning centers of magnetic flux are related closely to the occurrence mechanism of the magnetic effect.

• Progress in Superconductivity and Cryogenics
• /
• v.10 no.3
• /
• pp.19-22
• /
• 2008

The power systems should be improved to reduce the number of black-out events occurring throughout the world. Quantitative evaluation of composite power system reliability is very important in a competitive electricity environment. The reason is that the successful operation of electric power systems under a deregulated electricity market depends on transmission system reliability management. This paper presents sensitivity analysis of probabilistic reliability indices of Korea power systems with checking application of HTS-FCL.

• Journal of the Korean Ceramic Society
• /
• v.40 no.6
• /
• pp.530-538
• /
• 2003

Samples with the nominal composition, B $i_{1.84}$P $b_{0.34}$S $r_{1.91}$C $a_{2.03}$C $u_{3.06}$ $O_{10+}$$\delta$/ (110 K phase) high $T_{C}$ superconductors containing MgO as an additive were fabricated by a solid-state reaction method. Samples with 5~50 wt％ MgO were sintered at 820~86$0^{\circ}C$ for 24 h. The structural characteristics, critical temperature and grain size of the samples with different MgO contents were analyzed by XRD and SEM. As the MgO content increased, the intensity of MgO peaks and ratio of Bi-2212 phase in superconductors were intensified and the proportion of the phase transition from Bi-2223 to Bi-2212 was increased.d.creased.d.

• The Transactions of the Korean Institute of Electrical Engineers C
• /
• v.52 no.6
• /
• pp.241-248
• /
• 2003

$Bi_{1.84}Pb_{0.34}Sr_{1.91}Ca_{2.03}Cu_{3.06}O_{10+\delta}$ high $T_{c}$ superconductors containing Ag as an additive were fabricated by a solid-state reaction method. The superconducting properties, such as the structural characteristics, the critical temperatures, the grain size and the image of mapping on the surface were investigated. Samples with Ag and Au of 50 wt% each were sintered at various temperature(820~$850^{\circ}C$). The structural characteristics, the microstructure of surface and the critical temperature with respect to the each samples were analyzed by XRD and SEM, EDS and four-prove methode respectively. The critical temperature showed the result which the Ag additive samples are higher than Au additive samples. The microstructure of the surface showed the tendency which the Ag additive samples become more minuteness than Au additive samples.

• The Transactions of the Korean Institute of Electrical Engineers C
• /
• v.50 no.10
• /
• pp.494-499
• /
• 2001

The effects of accelerated Ultraviolet (UV) radiation on High temperature vulcanized (HTV), Room temperature vulcanized (RTV) silicone rubber and two types of ethylene propylene diene terpolymer (EPDM) used for composite insulator were investigated by hydrophobicity class (HC), surface voltage decay after corona charging, SEM-ES, FTIR and XPS. The contact angle in two kinds of silicone rubber was scarcely change, but EPDM occurred to the loss of hydrophobicity followed by surface cracking and chalking. The surface voltage decay on UV-treated silicone rubber and EPDM showed a different decay trend with UV treatment. EDS and XPS analysis indicated that the oxygen content increased with UV treatment time in all samples. For silicone rubber, the oxidized groups of inorganic silica-like structure increased with UV treatment time. The oxidized carbon of C=O, O=C-O in EPDM increased. These oxidized surface for each material had different electrostatic characteristics, so deposited charges were expected to have different impacts on their surface hydrophobicity. The degradation mechanism based on our results was discussed.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
• /
• v.16 no.6
• /
• pp.522-531
• /
• 2003

Samples with the nominal composition, B $i_{1.84}$P $b_{0.34}$S $r_{1.91}$C $a_{2.03}$C $u_{3.06}$ $O_{10+{\delta}}$ high- $T_{c}$ superconductors containing MgO as an additive were fabricated by a solid-state reaction method. Samples with MgO of 5~30 wt% each were sintered at 820~86$0^{\circ}C$ for 24 hours. The structural characteristics, critical temperature, grain size and image of mapping with respect to MgO contents were analyzed by XRD(X-Ray Diffraction), SEM(Scanning Electron Microscope) and EDS(Energy dispersive X-ray spectrometer) respectively. As MgO contents increased, intensity of MgO Peaks and ratio of Bi-2212 phase in superconductors intensified and the proportion of the phase transition from Bi-2223 to Bi-2212 was increased.

• Progress in Superconductivity and Cryogenics
• /
• v.10 no.1
• /
• pp.24-27
• /
• 2008

For the development of superconducting fault current limiters(SFCLs) having large current capacity, we fabricated an SFCL element that consists of Bi-2212 superconductor and Cu-Ni alloy tubes. First, Ag was plated on the surface of the Bi-2212 for the enhancement of soldering process. On the Ag-plated Bi-2212 tube, a Cu-Ni alloy tube was soldered using optimized solders and soldering conditions. The BSCCO/Cu-Ni composite was processed mechanically to have a helical shape for the improvement of the SFCL characteristics. The total current path of the SFCL element was 1330 mm long with 12 turns, and had critical current of 340 A at 77 K. Finally, we carried out the fault test using the fabricated SFCL element. It showed successful current limiting performance under the fault condition of 50 $V_{rms}$ and 5.5 kA. From the results, the rated voltage of the SFCL element was decided to be 0.4 V/cm, and the power capacity was 12 kVA at 77 K. The fabrication process of the SFCL and the fault test results will be presented.

• Korean Journal of Materials Research
• /
• v.4 no.1
• /
• pp.37-43
• /
• 1994

Y-Ra-Cu-0 oxide superconductors were fabricated by the sinter-forging method to make the critical current density improve through controlling of microstructure and crystal texture. The grain alignment of oxide superconductor was formed by the sinter-forging process and it's c-axis orientation was parallel to the press direction.The orientation factor of texture increased with sinking temperature and pressure, and also grain alignment was improved by the addition of Ag. As for the sinterforged Y-Ba-Cu-O/Ag sample, the $T_c$(on-set) was not almost varied with the sinter-forging temperature, but $T_c\;^{zero}$ decreased more or less at high sinter-forging temperatures. In addition, it was observed that added-Ag was mainly distributed along the grain boundar~es in the (123) matrix, resulting in the densification of microstructure. From these results, i t was thought that the improvement of $J_c$ over 2000A/$\textrm{cm}^2$ was attributed to the texture, densification of microstructure, and (123) grain growth due to the Ag addition.

• Progress in Superconductivity
• /
• v.10 no.1
• /
• pp.45-49
• /
• 2008

For the development of superconducting fault current limiters (SFCLs), fault current limiting elements were fabricated out of Bi-2212 bulk tubes and tested. The SFCL elements consisted of tube shaped Bi-2212 bulks and metal shunts for the stabilizers. Firstly, the Bi-2212 bulk tubes were processed based on a design of monofilar coils in order to acquire large resistance and high voltage rating. 300 mm-long Bi-2212 tubes were designed to have the current path of 410 cm in length with 24 turns and 41 mm in diameter. The processed monofilar coil, as designed, had 300 A $I_c$ at 77 K. The fabricated superconducting monofilar coils were affixed to Cu-Ni alloy as that of stabilizers. The Cu-Ni alloys were processed to have the same shape of the superconducting monofilar coils. The Cu-Ni coil had resistivity of 32 ${\mu}{\Omega}$-cm at 77 K and 37 ${\mu}{\Omega}$-cm at 300 K. The metal shunts were attached to the outside of the Bi-2212 monofilar coil by a soldering technique. After the terminals made of copper were attached to both ends of the superconductor-metal shunt composite, the gap between the turns and the surface of the elements was filled with an epoxy and a dense mesh made of FRP in order to enhance the mechanical strength. The completed SFCL elements went through fault tests, and we confirmed that the voltage rating of 143 $V_{rms}$ (E =0.35 $V_{rms}$/cm) could be accomplished.