Kideok Sim

Korea Electrotechnology Research Institute-KERI, Tsau-liang-hai, Busan, South Korea

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Publications (33)34.15 Total impact

  • [Show abstract] [Hide abstract]
    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.
    Physica C Superconductivity 01/2014; · 0.72 Impact Factor
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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%.
    IEEE Transactions on Applied Superconductivity 01/2014; 24(3):1-4. · 1.20 Impact Factor
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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.
    Journal of Superconductivity and Novel Magnetism 01/2013; 26(4). · 0.70 Impact Factor
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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.
    IEEE Transactions on Applied Superconductivity 01/2013; 23(3):5400804-5400804. · 1.20 Impact Factor
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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.
    IEEE Transactions on Applied Superconductivity 01/2013; 23(3):5400104-5400104. · 1.20 Impact Factor
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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.
    IEEE Transactions on Applied Superconductivity 01/2013; 23(3):5401804-5401804. · 1.20 Impact Factor
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    ABSTRACT: In case of long pieces of HTS conductor, their critical current measurement is an important process for the conductor manufacturer and the customer, however, it is very time consuming process. Conventional critical current measurement is carried out by ‘four probe method’, which increase the transport current and measure the voltage between the fixed voltage taps. Therefore, it consists of conductor moving and measuring process. To speed up the measuring process, longer distance between voltage taps is required. In this case, the measured critical current is averaged and small defects, which can be very crucial for thermal stability, cannot be found. Therefore, the limitation of the voltage tap length should be carefully decided considering the cooling environment. Another non-contact or indirect method is to measure the screening effect of magnetic field and converting the field signal to the critical current, which is called as hall probe method. This process is known as a very efficient way to find local defects and estimate the distribution of the critical current, however, it contains inevitable error and noise because it should measure the small magnetic field signals.This paper describes a new critical current measurement system, which have similar hardware structure of conventional ‘four probe method’. However, it is much faster than other systems using fast feedback control of the transport current while the conductor is continuously moving with high speed. The measured results are compared with the conventional method and hall probe method.
    Physica C Superconductivity 01/2013; 484:142–147. · 0.72 Impact Factor
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    ABSTRACT: The tri-axial high temperature superconducting (HTS) power cable design has several advantages when compared with other HTS power cables. However, this design has an imbalance in the three phase currents, as the phase conductors of the tri-axial HTS power cable have different radii. The radii of the phase conductors impact the value of inductance and capacitance for the cable, and the values are determined by the winding pitch length and the winding direction. Thus, the current imbalance can be minimized through the adjustment of the winding pitch length, the radius of each layer, and the winding direction. It takes a lot of time to manually calculate an impedance and to find a matched impedance. So the impedance of the tri-axial HTS power cable, according to its shape, was analyzed and the impedance matching program (IMP) was developed using LabVIEW (Laboratory Virtual Instrument Engineering Workbench) to solve this problem. IMP finds the matching impedance automatically by calculating the impedance according to the tri-axial HTS cable dimension. Consequently, this could save a lot of time, and so this program will be applied to the design of the tri-axial HTS power cable effectively.
    Journal of Superconductivity and Novel Magnetism 01/2013; 26(4). · 0.70 Impact Factor
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    ABSTRACT: According to the continuous development of coated conductors and compact cryocoolers, research and development efforts for High Temperature Superconducting (HTS) magnets are increasing using conduction cooling method. To increase the cooling efficiency and thermal stability of the HTS magnet, the coated conductor is wound by wet-winding or epoxy impregnating in vacuum after dry-winding. Due to the large Lorentz force and thermal contraction, stress analysis of the composite material, which is composed of HTS conductor, insulation layer and epoxy layer, is necessary to assure the mechanical stability of the HTS magnets.
    IEEE Transactions on Applied Superconductivity 01/2012; 22(3):7700804-7700804. · 1.20 Impact Factor
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    ABSTRACT: This paper describes new kind of HTS (High Temperature Superconducting) element for current leads, which can transfer large electric current in the nuclear fusion system. Since the HTS tapes have no resistance and the generated Joule heat is also very small compared to the conventional current leads, cooling costs of the current leads can be reduced. For this reason, the various feasibility researches for HTS current leads have been promisingly progressed in the superconducting power applications. However, there is a limitation on the capability of current carrying for single HTS tape. In addition, the cross-sectional area of the current leads should be small enough to minimize the heat conducted through the HTS current leads. In order to improve the current carrying capacity of the current leads, multiple HTS tapes are required. In this paper, we proposed several structures of compact HTS current leads and compare them other 2 kA class current leads. We report on the calculated characteristics of stabilized HTS current leads and on the performance measured during critical current measurement tests.
    IEEE Transactions on Applied Superconductivity 01/2012; 22(3):4801204-4801204. · 1.20 Impact Factor
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    ABSTRACT: Output power of the wind power generation system (WPGS) fluctuates due to wind speed variation and affects the frequency and voltage fluctuations of the utility. Superconducting Magnetic Energy Storage (SMES) can overcome these fluctuations because of fast response time for energy charging and discharging. To stabilize the frequency fluctuation, HTS SMES should be connected to the terminal of the WPGS. Ulleung island power network in Korea was modeled to demonstrate the effectiveness of SMES for frequency stabilization. Based on the simulation results using EMTDC, a toroidal-type HTS SMES cooled by conduction cooling method and a DC/DC chopper for current charging and discharging were fabricated for experiment. Power network including WPGS was implemented through a Real Time Digital Simulator (RTDS). The simulation and experimental results for frequency stabilization using real HTS SMES and RTDS are discussed in detail. KeywordsFrequency stabilization–HTS SMES–RTDS–Wind power generation system
    Journal of Superconductivity and Novel Magnetism 01/2011; 24(1):1007-1014. · 0.70 Impact Factor
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    ABSTRACT: Shimming is very important for nuclear magnetic resonance (NMR) magnets because image resolution is highly dependent on the homogeneity of the magnetic field. There are two types of shimming: active and passive. Active shimming is done using coils with adjustable current. Passive shimming involves pieces of steel with good magnetic qualities. The steel pieces are placed near a superconducting magnet. They are magnetized and produce their own magnetic field. Additional magnetic fields (produced by coils or steel) add to the original magnetic field of the superconducting magnet in such a way that the total field becomes more homogeneous. In this paper, we developed a passive shimming method adopting consecutive optimization techniques, i.e., linear programming (LP) and evolution strategy (ES). The LP is relatively fast and mostly guarantees a global minimum for a linear problem, whereas the ES is easy to formulate and can digitize design variables. So we suggested an optimization method combining both the LP and the ES consecutively for passive shimming of NMR magnets. KeywordsNMR/MRI magnet–Ferromagnetic shimming–Passive shimming–Linear programming–Evolution strategy
    Journal of Superconductivity and Novel Magnetism 01/2011; 24(1):1037-1043. · 0.70 Impact Factor
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    ABSTRACT: The Superconducting Magnetic Energy Storage (SMES) system is a key technology for overcoming the voltage sag, swell, interruption, and frequency fluctuation with the fast response speed of current charge and discharge. A toroidal-type SMES is designed using a 3D CAD program, and the inductance and AC loss characteristic during operation are analysed using Finite Element Method (FEM) program. The toroidal-type magnet consists of 30 double pancake coils (DPC). The single pancake coils (SPC), constituting the double pancake coils, are arranged at an angle of 6?? from each other, based on the central axis of the toroidal-type magnet. The conduction cooling method is used for the toroidal-type SMES cooling. To evaluate the characteristics of the over-mega-joule class grid-connected HTS SMES system, the authors implemented a simulation by which the SMES coil could be connected to the Real Time Digital Simulator (RTDS). Using the simulation, users can perform voltage sag and frequency stabilization simulations with a real SMES coil in real time and easily change the capacity of the SMES system as much as they need. The effectiveness of the toroidal-type HTS SMES system is demonstrated through the RTDS-based simulation and the results are briefly discussed.
    IEEE Transactions on Applied Superconductivity 07/2010; · 1.20 Impact Factor
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    ABSTRACT: Studies on (YBCO) coated conductor (CC) are actively underway for the practical application of high temperature superconducting (HTS) devices such as magnets, cables and fault current limiting devices because the CC has higher critical current characteristics under high temperature and magnetic field. However, it is hard to make a long-length of YBCO CC tape with uniform critical current density using the present processing techniques. The hot spot will emerge in a local region if the critical current is non-uniform along the HTS tape, and eventually, the hot spots may cause serious damage to the HTS tape. Therefore, it is important to examine the thermal stability characteristic of the YBCO CC tape from the quench protection point of view. In this paper, the segmental critical current of a YBCO CC sample tape is measured in liquid nitrogen, and a heater is installed at the center of the sample tape in order to examine the normal zone propagation characteristics in the longitudinal direction under the adiabatic condition with a Gifford-McMahon cryocooler. Measurements are performed as a function of heat input and transport current for the operating temperatures of 77 K, 65 K and 40 K, respectively, and the results are discussed in detail.
    IEEE Transactions on Applied Superconductivity 07/2010; · 1.20 Impact Factor
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    ABSTRACT: Numerical analysis of AC loss for a HTS power cable is investigated using commercial FEM software package. AC loss of the HTS power cable, which is made by 2 G conductor, is hard to experimentally measure due to very small signal compared to that made by 1G conductor. The FEM model describes current distribution and AC loss inside the HTS conductor for the AC transport current through nonlinear E-J correlation. For the verification of the AC loss analysis model, the results were compared with the well known analytic solution of a single strip HTS conductor and experiments. Unlike IBAD substrate, magnetization of the RABiTS has influence on the precise estimation of the AC loss and it is also considered in the FEM model. Moreover, several conductors should be stacked to meet the large transport current because of the small critical current at present and the effect of stacking configuration is also investigated. In this paper, AC loss analysis results are presented for various HTS power cable configurations such as stacking directions. The results are compared with the experimental results of a model HTS power cable and the best configuration to minimize AC loss is suggested.
    IEEE Transactions on Applied Superconductivity 07/2010; · 1.20 Impact Factor
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    ABSTRACT: 2nd generation high temperature superconducting (2G-HTS) tape consists of multi-layers such substrate, buffer layer, superconducting layer and reinforced lamination tapes. 2G HTS tape is a candidate of good materials for current lead of superconducting magnet system owing to its low thermal conductivity. However, joint resistance between 2G HTS tapes and terminal block can be a major problem because of high electrical resistivity of substrate, buffer layer and reinforced lamination tapes of 2G HTS. So specially considering joint resistance between 2G tapes and terminal block, 2G HTS current lead for 400 A was designed and fabricated. This current lead was consisting of two terminal blocks, a support bar or tube, protection tube and six 2G HTS tapes. Its total length was 300 mm and body diameter 18.3 mm. At liquid nitrogen temperature (77 K) critical current (Ic) of this HTS current lead was 600 A, about 1.5 times the operating current 400 A. Conductive heat loss of 2G HTS current lead between 60 K and 7 K was 50 mW.
    IEEE Transactions on Applied Superconductivity 07/2010; · 1.20 Impact Factor
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    ABSTRACT: This paper analyses operating characteristic of high temperature superconducting magnetic energy storage (HTS SMES) for frequency stabilization of dispersed power generation system. The wind power generation system (WPGS) fluctuates due to wind speed variation and affects the frequency and voltage fluctuations of the utility. SMES is probably a key technology to overcome these fluctuations. To stabilize power system frequency, a large-scale HTS SMES is connected to the terminal of the WPGS. The authors analysed the load side frequencies using two different configurations of SMES, one consisting of a single magnet and the other of a dual magnet. From the simulation results, it can be concluded that the SMES is a useful device for stabilizing the power system frequency fluctuations, and a dual magnet type SMES is more effective for frequency stabilizing but exhibits more AC loss due to the increased operating current than a single magnet type.
    IEEE Transactions on Applied Superconductivity 07/2010; · 1.20 Impact Factor
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    ABSTRACT: A method for estimating the current distribution on the HTS strands which is composed of the HTS power cable was developed. A group of hall sensors which are well-arranged around the HTS cable were used in measuring the circumferential magnetic field. The current distribution can be calculated by solving a matrix equation which contains the measured magnetic field values as its elements. The contribution of the magnetic field generated by each strand in each hall sensor should be known to solve the matrix equation. The contribution can be calculated by FEM analysis simulating the HTS cable or can be measured using a duplicated short HTS cable of which current terminals are modified to apply the current to each strand independently. A simple computer simulation was performed to investigate the feasibility of the method and the performance characteristics of the method was examined for the HTS cable which is composed of several HTS strands. In this paper, a simple mathematics for estimating the current distribution and the results of experiment using the designed and manufactured measuring apparatus will be introduced.
    IEEE Transactions on Applied Superconductivity 01/2010; 20(3):1981-1984. · 1.20 Impact Factor
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    ABSTRACT: This paper analyzed the heat characteristics of a conduction cooling toroidal-type SMES magnet. The authors designed and manufactured a conduction cooling toroidal-type SMES magnet which consists of 30 double pancake coils. One (a single pancake coil) of a double pancake coil is arranged at an angle of 6° from each other. The shape of the toroidal-type SMES magnet was designed by a 3D CAD program. The heat invasion was investigated under no-load condition and the thermal characteristic of the toroidal-type SMES magnet was analyzed using the Finite Elements Method program. Both the analyzed and the experiment results are compared and discussed in detail.
    Physica C Superconductivity 01/2010; 470(20):1711-1716. · 0.72 Impact Factor
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    ABSTRACT: In Korea, the superconducting power cable has been developed since 2001, with the basic specifications of 22.9 kV/50 MVA. The superconducting power cable can carry more than 2 to 5 times higher electric power compared with conventional ones. It is important to test the DC critical current related with its power capacity before applying to the real power grid. In 1995, several international standards organizations including IEC, decided to unify the use of statistical terms related with "accuracy" or "precision" in their standards. It was decided to use the word "uncertainty" for all quantitative (associated with a number) statistical expressions. In this paper, we measured DC critical current of 22.9 kV/50 MVA superconducting power cable with several voltage tap and analyzed the uncertainty with these results. These analyzed results can be applied the standardization of the superconducting power cable.
    IEEE Transactions on Applied Superconductivity 01/2010; 20(3):1272-1275. · 1.20 Impact Factor

Publication Stats

82 Citations
34.15 Total Impact Points

Institutions

  • 2006–2014
    • Korea Electrotechnology Research Institute-KERI
      Tsau-liang-hai, Busan, South Korea
  • 2009–2010
    • Changwon National University
      • Department of Electrical Engineering
      Changnyeong, South Gyeongsang, South Korea
  • 2006–2008
    • Yonsei University
      • Department of Electrical and Electronic Engineering
      Seoul, Seoul, South Korea