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REFERENCE LINKING PLATFORM OF KOREA S&T JOURNALS
> Journal Vol & Issue
Progress in Superconductivity and Cryogenics
Journal Basic Information
Journal DOI :
The Korea Institute of Applied Superconductivity and Cryogenics
Editor in Chief :
Volume & Issues
Volume 15, Issue 4 - Dec 2013
Volume 15, Issue 3 - Sep 2013
Volume 15, Issue 2 - Jun 2013
Volume 15, Issue 1 - Mar 2013
Selecting the target year
Progress in research and development for REBCO coated conductors by reactive co-evaporation
Oh, S.S. ; Kim, H.S. ; Ha, H.S. ; Ko, R.K. ; Ha, D.W. ; Lee, H. ; Moon, S.H. ; Yoo, S.I. ;
Progress in Superconductivity and Cryogenics, volume 15, issue 4, 2013, Pages 1~5
DOI : 10.9714/psac.2013.15.4.001
This paper reviews recent progress in research and development (R&D) of reactive co-evaporation for high performance REBCO coated conductors in Korea. Two types of reactive co-evaporation methods were developed for the deposition of SmBCO and GdBCO superconducting layers respectively on the IBAD (Ion Beam Assisted Deposition)-MgO template in the Korean coated conductor project. Batch type reactive co-evaporation equipment and its processing were developed for SmBCO coated conductors at Korea Electrotechnology Research Institute (KERI) in conjunction with the Korea Advanced Institute of Science and Technology (KAIST), and a very high critical current exceeding 1,000 A/cm at 77 K in the self field was achieved through the optimization of deposition parameters. Reel-to-reel type reactive co-evaporation processing with a high conversion rate was also developed, while long length GdBCO coated conductors have been routinely produced by SuNAM Co. The minimum critical current of 422 A/cm-w at 77 K in self field was confirmed for 1 km-long GdBCO tape.
The maintenance record of the KSTAR helium refrigeration system
Moon, K.M. ; Joo, J.J. ; Kim, N.W. ; Chang, Y.B. ; Park, D.S. ; Kwag, S.W. ; Song, N.H. ; Lee, H.J. ; Lee, Y.J. ; Park, Y.M. ; Yang, H.L. ; Oh, Y.K. ;
Progress in Superconductivity and Cryogenics, volume 15, issue 4, 2013, Pages 6~9
DOI : 10.9714/psac.2013.15.4.006
Korea Superconducting Tokamak Advanced Research (KSTAR) has a helium refrigeration system (HRS) with the cooling capacity of 9 kW at 4.5 K. Main cold components are composed of 300 tons of superconducting (SC) magnets, main cryostat thermal shields, and SC current feeder system. The HRS comprises six gas storage tanks, a liquid nitrogen tank, the room temperature compression sector, the cold box (C/B), the 1st stage helium distribution box (DB#1), the PLC base local control system interconnected to central control tower and so on. Between HRS and cold components, there`s another distribution box (DB#2) nearby the KSTAR device. The entire KSTAR device was constructed in 2007 and has been operated since 2008. This paper will present the maintenance result of the KSTAR HRS during the campaign and discuss the operation record and maintenance history of the KSTAR HRS.
Survival of the Insulator under the electrical stress condition at cryogenic temperature
Baek, Seung-Myeong ; Kim, Sang-Hyun ;
Progress in Superconductivity and Cryogenics, volume 15, issue 4, 2013, Pages 10~14
DOI : 10.9714/psac.2013.15.4.010
We have clearly investigated with respect to the survival of the insulator at cryogenic temperature under the electrical stress. The breakdown and voltage-time characteristics of turn-to-turn models for point contact geometry and surface contact geometry using copper multi wrapped with polyimide film for an HTS transformer were investigated under AC and impulse voltage at 77 K. Polyimide film (Kapton) 0.025 mm thick is used for multi wrapping of the electrode. As expected, the breakdown voltages for the surface contact geometry are lower than that of the point contact geometry, because the contact area of the surface contact geometry is lager than that of the point contact geometry. The time to breakdown t50 decreases as the applied voltage is increased, and the lifetime indices increase slightly as the number of layers is increased. The electric field amplitude at the position where breakdown occurs is about 80 % of the maximum electric field value. The relationship between survival probability and the electrical stress at cryogenic temperature was evident.
A comparative study on the flux pinning properties of Zr-doped YBCO film with those of Sn-doped one prepared by metal-organic deposition
Choi, S.M. ; Shin, G.M. ; Joo, Y.S. ; Yoo, S.I. ;
Progress in Superconductivity and Cryogenics, volume 15, issue 4, 2013, Pages 15~20
DOI : 10.9714/psac.2013.15.4.015
We investigated the flux pinning properties of both 10 mol% Zr-and Sn-doped
(YBCO) films with the same thickness of ~350 nm for a comparative purpose. The films were prepared on the
(STO) single crystal substrate by the metal-organic deposition (MOD) process. Compared with Sn-doped YBCO film, Zr-doped one exhibited a significant enhancement in the critical current density (
) and pinning force density (
). The anisotropic
ratio in the field-angle dependence of
at 77 K for 1 T was also improved from 0.23 for Sn-doped YBCO to 0.39 for Zr-doped YBCO. Thus, the highest magnetic
values of 9.0 and
with the maximum
) values of 19 and
at 65 and 77 K for H // c, respectively, could be achieved from Zr-doped YBCO film. The stronger pinning effect in Zr-doped YBCO film is attributable to smaller
(BZO) nanoparticles (the average size
(YBSO) nanoparticles (the average size
nm) incorporated in Sn-doped YBCO film since smaller nanoparticles can generate more defects acting as effective flux pinning sites due to larger incoherent interfacial area for the same doping concentration.
Performance inspection of smart superconducting fault current controller in radial distribution substation through PSCAD/EMTDC simulation
MassoudiFarid, Mehrdad ; Shim, Jae Woong ; Lee, Jiho ; Ko, Tae Kuk ;
Progress in Superconductivity and Cryogenics, volume 15, issue 4, 2013, Pages 21~25
DOI : 10.9714/psac.2013.15.4.021
In power grid, in order to level out the generation with demand, up-gradation of the system is occasionally required. This will lead to more fault current levels. However, upgrading all the protection instruments of the system is both costly and extravagant. This issue could be dominated by using Smart Fault Current Controller (SFCC). While the impact of Fault current Limiters (FCL) in various locations has been studied in different situations for years, the performance of SFCC has not been investigated extensively. In this research, SFCC which has adopted the characteristics of a full bridge thyristor rectifier with a superconducting coil is applied to three main locations such as load feeder, Bus-tie position and main feeder location and its behavior is investigated through simulation in presence and absence of small Distributed Generation unit (DG). The results show a huge difference in limiting the fault current when using SFCC.
A numerical study on the feasibility evaluation of a hybrid type superconducting fault current limiter applying thyristors
Nam, Seokho ; Lee, Woo Seung ; Lee, Jiho ; Hwang, Young Jin ; Ko, Tae Kuk ;
Progress in Superconductivity and Cryogenics, volume 15, issue 4, 2013, Pages 26~29
DOI : 10.9714/psac.2013.15.4.026
Smart fault current controller (SFCC) proposed in our previous work consists of a power converter, a high temperature superconducting (HTS) DC reactor, thyristors, and a control unit . SFCC can limit and control the current by adjusting firing angles of thyristors when a fault occurs. SFCC has complex structure because the HTS DC reactor generates the loss under AC. To use the DC reactor under AC, rectifier that consists of four thyristors is needed and it increases internal resistance of SFCC. For this reason, authors propose a hybrid type superconducting fault current limiter (SFCL). The hybrid type SFCL proposed in this paper consists of a non-inductive superconducting coil and two thyristors. To verify the feasibility of the proposed hybrid type SFCL, simulations about the interaction of the superconducting coil and thyristors are conducted when fault current flows in the superconducting coil. Authors expect that the hybrid type SFCL can control the magnitude of the fault current by adjusting the firing angles of thyristors after the superconducting coil limits the fault current at first peak.
Operation characteristics of SFCLs combined with a transformer in three-phase power system
Jung, B.I. ; Choi, H.S. ;
Progress in Superconductivity and Cryogenics, volume 15, issue 4, 2013, Pages 30~33
DOI : 10.9714/psac.2013.15.4.030
The studies of superconducting fault current limiter (SFCL) for reduction of the fault current are actively underway in the worldwide. In this paper, we analyzed the characteristics of a new type SFCL using the conventional transformer and superconducting elements combined mutually. The secondary and third windings of this SFCL were connected the load and the superconducting element, respectively. The electric power was provided to load connected to secondary windings of the transformer in normal state of power system. On the other hand, when the fault occurred in power system, the fault current was limited by closing the line of third winding of the transformer. At this time, the ripple phenomenon of the fault was minimized by opening the fault line in secondary winding of a transformer in power system. The sensing of the fault state was performed by the CT(current transformer) and then turn-on and turn-off switching behavior of the SFCL was performed by the SCR(silicon-controlled rectifier). As a result, the proposed SFCL limited the fault current within a half-cycle efficiently. We confirmed that the fault current limitation rate was changed according to the winding ratio of a transformer.
Characteristics of the SFCL by turn-ratio of three-phase transformer
Jeong, I.S. ; Choi, H.S. ; Jung, B.I. ;
Progress in Superconductivity and Cryogenics, volume 15, issue 4, 2013, Pages 34~38
DOI : 10.9714/psac.2013.15.4.034
According to the increase of electric consumption nowadays, power system becomes complicated. Due to this, the size of single line-to-ground fault from power system also increases to have many problems. In order to resolve these problems effectively, an Superconducting Fault Current Limiter(SFCL) was proposed and continuous study has been done. In this paper, an SFCL was combined to the neutral line of a transformer. An superconductivity has the characteristics of zero resistance below critical temperature. because of this, SFCL has nearly zero resistance. so we connecting SFCL to neutral line will not only have any loss in the normal operation but also have the less burden of electric power because of only limiting the initial fault current. We analyzed the characteristics of current, voltage according to the changes of turn ratio of 3 phase system in case of combinations of an SFCL to the neutral line. It was confirmed that the limiting rate of initial fault current by the increase of turn ratio was reduced.
Influence of end-joint methods on magnetization loss in striated helical conductors
Kim, Woo-Seok ; Kim, Yungil ; Choi, Kyeongdal ; Lee, Ji-Kwang ;
Progress in Superconductivity and Cryogenics, volume 15, issue 4, 2013, Pages 39~43
DOI : 10.9714/psac.2013.15.4.039
To reduce the magnetization loss of a coated conductor, the striation and the transposition have to be accomplished for magnetic decoupling. The loss reduction effect in incomplete as well as complete striated YBCO CCs was reported in previous research. At the case of the incomplete striated sample, the end region of the sample is non-striated. So, it is not jointed with each other. In power applications, the joint is needed because current leads must be connected with HTS coils. In this research, the influence of end-joint methods with copper and superconducting joint on magnetization loss in striated YBCO CC and spiral winding samples are presented and compared with non-striated measured result.
Temperature dependency of magnetic field drifts of HTS pancake coils for NMR/MRI applications
Choi, Kyeongdal ; Lee, Seyeon ; Kim, Woo-Seok ; Lee, Sang Min ;
Progress in Superconductivity and Cryogenics, volume 15, issue 4, 2013, Pages 44~47
DOI : 10.9714/psac.2013.15.4.044
We had proposed a winding method so called "Wind-and-Flip", which enables a persistent current operation of an HTS pancake coil without any electrical joint. In order to improve the magnetic field drift characteristics, a prototype HTS coil with the technique was fabricated, and tested under various temperatures. Because the coil doesn`t have any electric terminals for current leads, an HTS background magnet was used to induce the persistent current in the coil by field cooling process. A conduction cooling system with a GM cryocooler was prepared to keep the operating temperatures of the prototype coil much below the 77 K. We investigated the magnetic field drift characteristics under the various operating temperatures by measuring the center magnetic field with a cryogenic Hall sensor. The persistent current mode operation at 20 ~ 50K showed a strong possibility of the winding technique for the application such as MRI or NMR.
Comparison of superconducting generator with 2G HTS and MgB
Park, S.I. ; Kim, J.H. ; Le, T.D. ; Kim, H.M. ;
Progress in Superconductivity and Cryogenics, volume 15, issue 4, 2013, Pages 48~52
DOI : 10.9714/psac.2013.15.4.048
This paper compares the features of second generation (2G) High Temperature Superconducting (HTS) field coil with those of magnesium diboride (
) field coil for a 10 MW class superconducting generator. Both coils can function effectively in their respective magnetic flux density range: 10-12 T for 2G HTS field coil, 2 T for
superconducting field coil. Even though some leading researchers have been developing 10 MW class superconducting generator with 2G HTS field coil, other research groups have begun to focus on
wire, which is more economical and suitable for mass production. However 2G HTS wire is still appealing in functions such as in-field property and critical temperature, it shows higher in-field property and critical temperature than
Commissioning result of the KSTAR in-vessel cryo-pump
Chang, Y.B. ; Lee, H.J. ; Park, Y.M. ; Lee, Y.J. ; Kwag, S.W. ; Song, N.H. ; Park, D.S. ; Joo, J.J. ; Moon, K.M. ; Kim, N.W. ; Yang, H.L. ; Oh, Y.K. ;
Progress in Superconductivity and Cryogenics, volume 15, issue 4, 2013, Pages 53~58
DOI : 10.9714/psac.2013.15.4.053
KSTAR in-vessel cryo-pump has been installed in the vacuum vessel top and bottom side with up-down symmetry for the better plasma density control in the D-shape H-mode. The cryogenic helium lines of the in-vessel cryo-pump are located at the vertical positions from the vacuum vessel torus center 2,000 mm. The inductive electrical potential has been optimized to reduce risk of electrical breakdown during plasma disruption. In-vessel cryo-pump consists of three parts of coaxial circular shape components; cryo-panel, thermal shield and particle shield. The cryo-panel is cooled down to below 4.5 K. The cryo-panel and thermal shields were made by Inconel 625 tube for higher mechanical strength. The thermal shields and their cooling tubes were annealed in air environment to improve the thermal radiation emissivity on the surface. Surface of cryo-panel was electro-polished to minimize the thermal radiation heat load. The in-vessel cryo-pump was pre-assembled on a test bed in 180 degree segment base. The leak test was carried out after the thermal shock between room temperature to
one before installing them into vacuum vessel. Two segments were welded together in the vacuum vessel and final leak test was performed after the thermal shock. Commissioning of the in-vessel cryo-pump was carried out using a temporary liquid helium supply system.
Conductive link between cryocooler and magnet in cryogen-free LTS magnet system
Choi, Yeon Suk ;
Progress in Superconductivity and Cryogenics, volume 15, issue 4, 2013, Pages 59~62
DOI : 10.9714/psac.2013.15.4.059
The conductive link is used as a cooling medium between a cryocooler and magnet in a cryogen-free superconducting magnet system. The low temperature superconducting (LTS) magnet has one solenoidal configuration with a metal former which has a 52 mm room temperature bore. The superconducting coil is installed in the cryostat maintaining high vacuum and cooled by a two-stage cryocooler. In order to maintain the operating temperature of magnet at the designed level, the cold head temperature of the cryocooler must be lower so that heat can be removed from the superconducting coil. Also, temperature difference is occurred between the magnet and cryocooler and its magnitude is dependent upon the contact resistance at the interfacial surface between metals in the conductive link. In the paper, the performance of the LTS magnet is investigated with respect to the conductive link between the magnet former and the cold head of the cryocooler. The effects of the contact pressure and interfacial materials on the temperature distribution along the conductive link are also presented.