Kideok Sim

Korea Electrotechnology Research Institute-KERI, Busan, Busan, South Korea

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Publications (43)43.05 Total impact


  • No preview · Article · Jan 2016 · IEEE Transactions on Applied Superconductivity

  • No preview · Article · Jan 2016 · IEEE Transactions on Applied Superconductivity
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    ABSTRACT: The HTS power cable is cooled by the circulation of liquid nitrogen. The cooling capacity of refrigerator increases with cable length. As the length of power cable increases, a joint box should be installed to reduce the cooling capacity and pressure drop for unit cooling system. The type of joint box can be divided into two groups. There are NJB(Normal Joint Box) and SJB(Stop Joint Box). Generally, SJB can separate each cooling system. In case of long distance DC cable, it is necessary to separate the cooling line in the regular distance of cooling system so SJB should be used. However, SJB, which has a difference from the insulation method of existing joint box, uses solid electrical insulation method. At the primary cooling time, thermal stress is generated by the temperature difference between the internal and external epoxy. So to prevent the damage stress analysis is required for the electrical insulation structure of SJB. In this paper, using the FEM analysis we study the cooling method and optimal shape of SJB to reduce the thermal stress result from temperature difference during the cooling time.
    Preview · Article · Dec 2015
  • Kyubong Lee · Kideok Sim · Changyoung Lee · Seokho Kim
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    ABSTRACT: The high temperature superconducting (HTS) magnet has been developed for the high magnetic field applications such as NMR, MRI and other industrial machinery. In designing process of these HTS magnets, the accurate estimation on the critical current (Ic) is essential to predict and secure the electromagnetic performance. The critical current of 2G HTS tape has anisotropic Ic degradation characteristics with the application of magnetic field – angular dependency of critical current. It is known that the perpendicular magnetic field to the face of HTS tape makes dominant degradation on the critical current for conventional 2G HTS tape. However, recently developed 2G HTS tape has more complex characteristics due to the artificial pinning center. Therefore, the method for Ic estimation reflecting such characteristics of 2G HTS tape needs to be devised. The method considering the angular dependency is introduced in this paper. And the result of newly devised method is compared with that of previous method. © 2015 Korea Institute of Applied Superconductivity and Cryogenics. All rights reserved.
    No preview · Article · Sep 2015 · Progress in Superconductivity and Cryogenics (PSAC)/Journal of the Korea Institute of Applied Superconductivity and Cryogenics
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    ABSTRACT: The transient characteristics of the tri-axial High Temperature Superconducting (HTS) power cable are different from those of a conventional power cable depending on whether the cable is under a steady or transient state due to the quench. Verification using simulation tools is required to confirm both the characteristics of the cable and the effect of the cable when it is applied to a real utility. However, a component for the cable has not been provided in simulation tools; thus the RTDSbased model component of the tri-axial HTS power cable was developed, and a simulation was performed under the transient state. The considered properties of model component include resistance, reactance and temperature. Simulation results indicate the variation of HTS power cable condition. The results are used for the transient characteristic analysis and stability verification of the tri-axial HTS power cable. In the future, the RTDS-based model component of the cable will be used to implement the hardware-in-the-loop simulation with a protection device.
    No preview · Article · Sep 2015 · Journal of Electrical Engineering and Technology
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    ABSTRACT: In this note, the effectiveness of voltage tap clipping technique was assessed in evaluating the electromechanical properties of high temperature superconductor (HTS) tapes in the aspect of practical device applications. In the four-probe transport I c measurement, instead of directly soldering the voltage lead wires onto the HTS samples, they were tapped to the sample by either just clipping or soldering them to the clips. This technique facilitated the simultaneous and repeated retained I c measurement test for multiple samples. Finally, the critical double bending diameter of HTS tapes and the electrical properties of jointed and striated coated conductor tapes could be easily determined.
    Full-text · Article · Aug 2015 · The Review of scientific instruments
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    ABSTRACT: We had developed four years ago a superconducting property measurement system (SPMS) that can be used to acquire electrical and thermal properties of high-temperature superconductor (HTS) tape samples. The SPMS was composed of the sample holder for mounting an HTS tape and 3 T HTS magnet, both cooled individually by conduction using a cryocooler. The maximum dimension of the HTS tape sample that could be loaded on the sample holder was 15 mm in width and 250 mm in length. The conduction-cooled sample holder was again fabricated to increase the maximum test current up to 800 A. Maximum transport current was 763 A in magnetic field intensity 3 T. The measuring temperature range was 15-50 K.
    No preview · Article · Jun 2015 · IEEE Transactions on Applied Superconductivity
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    ABSTRACT: In general, conventional induction heating system is designed only for a specific metal billet or object, because the heating system should be specialized to guarantee the best performance regarding heating quality and efficiency. It has been applied to large heating systems in metallic processing industries. A DC induction heating method using HTS magnets can be one of the better counterplans for higher efficiency and multi-purpose heating system. In this paper, we evaluated a performance of a 10 kW-class multi-purpose HTS DC induction heating machine without additional function or equipment, and performed efficiency analysis on various metals, including aluminum, copper, and iron billets. In addition, heating characteristics of other materials were simulated and analyzed through finite elements method (F.E.M.) models. The results demonstrate that the 2G HTS DC induction heating machine is applicable for all the ferrous and nonferrous metals and useful for large scale industrial applications.
    Full-text · Article · Jun 2015 · IEEE Transactions on Applied Superconductivity
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    ABSTRACT: Tri-axial high-temperature superconducting (HTS) power cables are very efficient compared with other HTS power cables due to their reduced use of HTS wires and cryogenic surface area, resulting from the mutually layered structure of the three phases. However, the operating characteristics of tri-axial HTS power cables differ from other cables in a transient-state condition. In order to install HTS power cables in a real grid, feasibility verification through simulation or experimentation is required in advance. Thus, the authors design a tri-axial HTS power cable and implement a power hardware-in-the-loop simulation that consists of a real time digital simulator-based simulation model and hardware devices including a power supply and a 1 m-long tri-axial HTS model cable. Simulation results show the stability verification under steady-state and transient-state conditions.
    Full-text · Article · Dec 2014 · Physics Procedia
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    ABSTRACT: Conventional induction heaters have been in operation in metal and related industries with poor energy efficiencies of only 50∼60%. Also, the efficiency of atmosphere furnace, one of the various heating facilities for metal billets, is about 20%. Hence, a high temperature superconducting (HTS) DC induction heating machine to heat a rotating metal billet under uniform magnetic field generated by the 2G HTS magnet with about 80∼90% of the system energy efficiency has been researched in this paper. We presented practical design specification, operational characteristics, and temperature distribution on a 10 kW class HTS DC induction heating machine which had been built and tested. The saturated temperature of an HTS no-insulated(NI) coil in the cryostat fabricated with 100 A of the operating current reached 45.9 K and the magnetic field at the centre point between two iron cores measured 0.2 T. The rotating machine for 4.1 kg of the aluminium billet was tested on 1,760 rpm of the rated rotating speed. The final temperature of the aluminium billet has risen up to 500 °C for 480 seconds. The research outcomes are expected to be useful for the design of a large scale HTS DC induction heating machine in industries.
    Full-text · Article · Sep 2014 · Physica C Superconductivity
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    ABSTRACT: HTS power cable bypass the fault current through the former to protect superconducting tapes. On the other hand, the fault current limiting (FCL) power cable can be considered to mitigate the fault current using its increased inductance and resistance. Using the increased resistance of the cable is similar to the conventional resistive fault current limiter. In case of HTS power cable, the magnetic field of HTS power cable is mostly shielded by the induced current on the shield layer during normal operation. However, quench occurs at the shield layer and its current is kept below its critical current at the fault condition. Consequently, the magnetic field starts to spread out and it generates additional inductive impedance of the cable. The inductive impedance can be enhanced more by installing materials of high magnetic susceptibility around the HTS power cable. It is a concept of SFCL power cable. In this paper, a sample SFCL power cable is suggested and experimental results are presented to investigate the effect of iron cover on the impedance generation. The tests results are analyzed to verify the generation of the inductive and resistive impedance. The analysis results suggest the possible applications of the SFCL power cable to reduce the fault current in a real grid.
    Full-text · Article · Jun 2014 · Progress in Superconductivity and Cryogenics (PSAC)/Journal of the Korea Institute of Applied Superconductivity and Cryogenics
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    ABSTRACT: The critical current, Ic of HTS superconducting tapes can be measured by transport or contactless method. Practically, the transport method using the four-probe method is the most common. In this study, a simple test procedure by clipping the voltage lead taps have been introduced instead of soldering which reduces time and effort and thereby achieving a much faster measurement of Ic. When using a pair of iron clips, Ic value decreased as compared with the measured one by standard method using soldered voltage taps and varies with the width of the clipped specimen part. However, when using a pure Cu clip, both by clipping and by soldering voltage taps give a comparable result and Ic measured are equal and close to the samples specification. As a result, material to be used as voltage clip should be considered and should not influence the potential voltage between the leads during Ic measurement. Furthermore, the simulation result of magnetic flux during Ic measurement test showed that the decrease of Ic observed in the experiment is due to the magnetic flux density, By produced at the clipped part of the sample by the operating current with iron clips attached to the sample.
    No preview · Article · Jun 2014 · Progress in Superconductivity and Cryogenics (PSAC)/Journal of the Korea Institute of Applied Superconductivity and Cryogenics
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    ABSTRACT: Nonuniformity of critical current, Ic is one of the most important factors to be considered for the practical applications of high-temperature superconducting (HTS) REBCO coated conductors. To investigate the variation of Ic due to mechanical strain, local critical currents were measured at various tensile strain values from 0 to 1.2% for brass-laminated GdBCO tapes at 77 K, and analyzed using the Weibull distribution function. Measured local critical currents vary and decrease significantly at strain levels above about 0.8%. The Weibull function with three parameters turned out to be applicable for describing the Ic distribution of REBCO HTS wire for the entire strain range. The statistical minimum Ic calculated from the Weibull distribution function decreased with increased tensile strain. The degree of Ic variation was observed to drastically increase when the applied tensile strain exceeded the irreversible strain of about 0.8%.
    Full-text · Article · Jun 2014 · IEEE Transactions on Applied Superconductivity
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    ABSTRACT: The authors presented practical fabricated specifications of a prototype 10kW class high-temperature superconductor (HTS) direct current (DC) induction heating machine and analyzed its operational characteristics including the system’s efficiency and the temperature distribution of the aluminum billet in detail In this paper, we discussed the fabrication process and focused particularly on the practical operating results of the HTS DC induction heating machine. The major operating characteristics of the HTS magnet under each stage were analyzed in detail. Detailed efficiency was investigated through the measuring of the realtime motor input and the billet temperature. Through a monitoring system, critical parameters were measured in real-time operation. The total heating time to 500 ∘C of the billet’s temperature was 400 s at 0.25 T at the center of the billet. These research outcomes are expected to be useful for the commercial design of a large-scale 2G HTS DC induction furnace for industrial fields.
    Full-text · Article · Feb 2014 · Journal of Superconductivity and Novel Magnetism
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    ABSTRACT: Tri-axial high temperature superconducting (HTS) power cables are being developed to maximize their advantages, which include reducing amount of HTS wires, having a low-leakage magnetic field, and being compact compared to different types of HTS power cables. However, a drawback of HTS power cables is their inherent imbalance impedance, which is due to an asymmetrical structure on each phase. To solve this problem, the phases must be transposed. The authors designed a distribution class tri-axial HTS power cable, as well as a transposition-based connection scheme for the cable. The phases of the cable were connected to each other via transposition through their cross-connections. This was achieved with an insulated support structure with three walled-off areas for insulation between three the phases, as well as transposition conductors, including copper base and HTS wires. In this paper, a distribution class tri-axial HTS power cable and a connection scheme for it are designed. The results, including the transposition-based joint box design, are described in detail. The connection scheme will be applied to the joint box of the cable for high-capacity and long-distance transmission.
    Full-text · Article · Jan 2014 · IEEE Transactions on Applied Superconductivity
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    ABSTRACT: Fault current limiting (FCL) cable is a kind of superconducting cable which has a function of limiting the fault current at the fault of power grid. The superconducting cable detours the fault current through its stabilizer to keep the temperature as low as possible. On the other hands, the FCL cable permits the temperature rise within some acceptable limit and the fault current is limited by the consequent increase of the resistance of superconducting cable. This kind of FCL cable is called 'resistive FCL cable' because it uses resistive impedance to limit the fault current. In this paper, we suggest a novel concept of FCL cable, which is named as 'inductive FCL cable'. The inductive FCL cable is similar as the magnetic shielding fault current limiter in its operating mechanism. The magnetic field of superconducting cable is almost perfectly shielded by the induced current at the shielding layer during its normal operation. However, at the fault condition, quench occurs at the shielding layer by the induced current higher than its critical current and the magnetic field is spread out of the shielding layer. It will induce additional inductive impedance to the superconducting cable and the inductive impedance can be increased more by installing some material with high magnetic susceptibility around the superconducting cable. We examined the feasibility of inductive FCL cable with simple elemental experiments. The current limiting performance of inductive FCL cable was estimated considering an arbitrary power grid and its fault condition.
    Full-text · Article · Sep 2013 · Progress in Superconductivity and Cryogenics (PSAC)/Journal of the Korea Institute of Applied Superconductivity and Cryogenics
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    ABSTRACT: Tri-axial high-temperature superconducting (HTS) power cables are being developed to maximize their advantages such as reduced amount of HTS wires, a low-leakage magnetic field, and compactness compared with the different types of HTS power cables. The authors designed a 22.9 kV/50 MVA-class tri-axial HTS power cable core to apply to the distribution system in Korea. The inherent imbalance in the three-phase currents of the tri-axial HTS power cable core was calculated using the impedance matching program. A tri-axial HTS power cable core was fabricated using second-generation YBCO wires and the cable core was tested under 77 K liquid nitrogen to verify the performance of the cable core through obtaining its electrical characteristics data. This paper describes the results of the design, fabrication, and evaluation of the 22.9 kV/50 MVA-class tri-axial HTS power cable core. They will be used to develop a tri-axial HTS power cable for the distribution system.
    No preview · Article · Jun 2013 · IEEE Transactions on Applied Superconductivity
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    ABSTRACT: We are now developing a high-temperature superconducting (HTS) dc cable system with the purpose of installing and operating the system on a real power grid in Cheju-island in 2013. As part of the development process, the basic design of the 250 MW HTS cable core was performed. In this paper, the key technical issues focused on the design of dc HTS cable core will be addressed and some important design results to satisfy the requirements of the power network will be presented.
    No preview · Article · Jun 2013 · IEEE Transactions on Applied Superconductivity
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    ABSTRACT: The characteristics of the tri-axial high temperature superconducting (HTS) power cable are different from a general copper cable, depending on whether the cable is under steady state or transient state, which is caused by quench. Before applying the tri-axial HTS power cable to a real utility, the system should be analyzed using certain simulation tools in order to confirm the effects of the cable on the real utility. However, a component that has the same impedance characteristics as the real tri-axial HTS power cable is not provided in simulation tools. In this paper, a model component for the tri-axial HTS power cable was developed in PSCAD/EMTDC. The developed model component included characteristics of the HTS cable, such as resistance, reactance, and temperature variation. The model component for the tri-axial HTS power cable was applied to a model power system and a simulation was performed under transient state. The simulation results show the effect of the tri-axial HTS power cable on the power system, the variation of quench resistance, and the temperature of the cable under fault conditions according to superconducting characteristics. The results of this work will be used to analyze the transient characteristics of other types of HTS power cables.
    No preview · Article · Jun 2013 · IEEE Transactions on Applied Superconductivity
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    ABSTRACT: Recently, triaxial high temperature superconducting (HTS) power cables have become a mainstream design in the development of HTS cables because of several advantages, such as the reduced amount of HTS wire, low leakage fields, and compactness, when compared with other types of HTS cable. Unlike the AC loss from other types of HTS cable, the AC loss from the triaxial HTS cable is influenced by the magnetic fields of other phases, as the triaxial HTS cable does not have a shield layer between the phase conductors. The authors have designed a 22.9 kV/50 MVA class triaxial HTS power cable. The AC loss and the magnetic characteristics of the triaxial HTS power cable are analyzed using the Comsol program, a commercial finite element method. To confirm the characteristics of the triaxial HTS power cable by wire type, the characteristics of two wire types were applied to the FEM model.
    No preview · Article · Apr 2013 · Journal of Superconductivity and Novel Magnetism

Publication Stats

179 Citations
43.05 Total Impact Points

Institutions

  • 2006-2015
    • Korea Electrotechnology Research Institute-KERI
      Busan, Busan, South Korea
    • Yonsei University
      • Department of Electrical and Electronic Engineering
      Seoul, Seoul, South Korea
  • 2009
    • Changwon National University
      • Department of Electrical Engineering
      창녕읍, Gyeongsangnam-do, South Korea