• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.22 no.1
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• pp.113-117
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• 2008

We investigated the current limiting and the recovery characteristics of a flux-lock type superconducting fault current limiter(SFCL) according to the winding directions. The flux-lock type SFCL consists of two coils. The primary coil was wound in parallel to the secondary coil through an Iron core, and the secondary coil was connected with the superconducting element in series. We have changed the winding direction of coils to compare the resistive type SFCL with the flux-lock type SFCL. The current limiting and the recovery characteristics were dependent on the winding direction. The quenching time in the additive polarity winding was faster than that of the subtractive polarity winding or the resistivity type. A consumed energy in a superconducting element was represented as $W= VIt=I^2Rt$. We found that there was a difference in the consumed energies in accordance with winding types because of differences in voltages imposed on a superconducting element in accordance with a winding direction.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2003.05a
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• pp.65-68
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• 2003

Interconnected power system operation has given rise to the problem of increased fault levels and leads to over stressing of all the components. Use have been made of recently developed high Tc superconductor in devising a superconducting fault current limiter (SFCL) that promises optimum performance in terms of capital cost, size, auto sensing, operational losses, response time and reliability. Recently, research about the application of the SFCL is actively progressing in Korea. To be applied for SFCL practically, the electrical insulation design of SFCL must be developed. Therefore, this paper presents the result of an investigation of the dielectric characteristics of turn-to-turn insulation for SFCL in liquid nitrogen. The dielectric characteristics of turn-to-turn insulation models of SFCL were investigated. We obtained following results. The breakdown voltages increased as the spacer thickness and length increased. And the breakdown voltages of turn-to-turn model without spacer were higher than the breakdown voltages of turn-to-turn model with spacer under impulse as well as AC voltages. The information gathered in this test series should be helpful in the design of liquid nitrogen filled SFCL.

• Journal of Mechanical Science and Technology
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• v.20 no.8
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• pp.1256-1265
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• 2006

The supersonic flows around tandem cavities were investigated by two-dimensional and three-dimensional numerical simulations using the Reynolds-Averaged Navier-Stokes (RANS) equation with the k- ω turbulence model. The flow around a cavity is characterized as unsteady flow because of the formation and dissipation of vortices due to the interaction between the freestream shear layer and cavity internal flow, the generation of shock and expansion waves, and the acoustic effect transmitted from wake flow to upstream. The upwind TVD scheme based on the flux vector split with van Leer's limiter was used as the numerical method. Numerical calculations were performed by the parallel processing with time discretizations carried out by the 4th-order Runge- Kutta method. The aspect ratios of cavities are 3 for the first cavity and 1 for the second cavity. The ratio of cavity interval to depth is 1. The ratio of cavity width to depth is 1 in the case of three dimensional flow. The Mach number and the Reynolds number were 1.5 and $4.5{\times}10^5$, respectively. The characteristics of the dominant frequency between two- dimensional and three-dimensional flows were compared, and the characteristics of the second cavity flow due to the first cavity flow was analyzed. Both two dimensional and three dimensional flow oscillations were in the 'shear layer mode', which is based on the feedback mechanism of Rossiter's formula. However, three dimensional flow was much less turbulent than two dimensional flow, depending on whether it could inflow and outflow laterally. The dominant frequencies of the two dimensional flow and three dimensional flows coincided with Rossiter's 2nd mode frequency. The another dominant frequency of the three dimensional flow corresponded to Rossiter's 1st mode frequency.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.62 no.1
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• pp.143-148
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• 2013

When the fault occurs in power system, the fault-current exceeds breaking capacity of the circuit breaker. So, reliablity of the power system is decreased sharply. Superconducting fault-current limiter (SFCL) is operated without impedance in normal state. The fault-current is limited by its impedance during the fault condition. However, the SFCL has several weak points such as huge size, high-price, liquid-nitrogen operation for the real power system. In this paper, We suggested the high-speed interrupter to limit the fault-current in case of the single line-to-ground fault. In addition, we compared the high-speed interrupter with the SFCL to ensure the operation reliability. The proposed interrupter detected the fault-current through the CT, and the power was supplied by operation of the SCR control system. In this experiment, the power of high-speed interrupter was applied after the 4.8[msec] from fault instant. The on-off operation of the interrupter was started after half-cycle from the fault. The fault-current was flowed into the impedance element by the switching operation of the high-speed interrupter. So, the fault current was limited within one cycle, and then it didnt exceed the capacity of a circuit breaker. We confirmed that there was slight difference between the SFCL with high-speed interrupter in terms of limiting-time of the fault-current and switching speed of the SCR. The high-speed interrupter was considered to be more efficient than the SFCL in size, cost or reliability.

• Proceedings of the Korean Institute of IIIuminating and Electrical Installation Engineers Conference
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• 2006.05a
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• pp.432-434
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• 2006

We investigated the quench characteristics of a flux-lock type superconducting fault current limiter (SFCL) according to the number of the superconducting elements at the subtractive polarity winding of a transformer. The flux-lock type SFCL consists of the transformer with a primary winding and two secondary windings connected in parallel, and the superconducting element was connected with secondary winding in series, respectively. The applied voltage at that tin was 200V. when two superconducting elements of the secondary winding was connected in parallel, the peak lie current increased up to 99A, while that flowing in a superconducting element in conventional flux-lock type SFCL showed 50A under the same conditions, the impedance of secondary winding under the same situation showed the opposite behavior. This enabled the parallel structure to be easy to increase the capacity of power system, in the meantime, The quench between two superconducting elements in the SFCL with two secondary windings connected in parallel was achieved simultaneously. While the quench-starting point was slightly different in the SFCL with two superconducting elements connected in series. We found that the parallel connection between the secondary windings increased the power capacity and let quench characteristics improve through their mutual linkage.

• Journal of Power Electronics
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• v.17 no.3
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• pp.821-834
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• 2017

This paper reports on a single-inductor multiple-output step-up converter with digital control. A systematic analog-to-digital-controller design is explained. The number of digital blocks in the feedback path of the proposed converter has been decreased. The simpler digital pulse-width modulation (DPWM) architecture is then utilized to reduce the power consumption. This architecture has several advantages because counters and a complex digital design are not required. An initially designed unit-delay cell is adopted recursively for the construction of coarse, intermediate, and fine delay blocks. A digital limiter is then designed to allow only useful code for the DPWM. The input voltage is 1.8 V, whereas output voltages are 2 V and 2.2 V. A co-simulation was also conducted utilizing PowerSim and Matlab/Simulink, whereby the 55 nm process was employed in the experimental results to evaluate the performance of the architecture.

• Proceedings of the KIEE Conference
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• 2005.07b
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• pp.960-962
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• 2005

In this paper, we investigated the quench characteristics of high-Tc superconducting(HTSC) elements in the integrated three-phase flux-lock type superconducting fault current limiter(SFCL) according to fault types such as the single-line-to-ground fault, the double-line-to-ground fault, the line-to-line fault and the triple-line-to-ground fault. The integrated three-phase flux-lock type SFCL is an upgrade version of single-phase flux-lock type SFCL. The structure of the integrated three-phase flux-lock type SFCL consisted of a three-phase flux-lock reactor wound on an iron core with the ratio of the same turn between coil 1 and coil 2 in each phase. When the SFCL is under the normal condition, the flux generated in the iron core is zero because the flux generated between two coils of each single phase is canceled out. Therefore, the SFCL's impedance is zero, and the SFCL has negligible influence on the power system. However, if a fault occurs in any single one of three phases, the flux generated in the iron core is not zero any more. The flux makes HTSC elements of all phases to quench irrespective of the fault type, which reduces the current in fault phase as well as the current of sound phase. It was obtained that the fault current limiting characteristics of the suggested SFCL were dependent on the quench characteristics of HTSC elements in all three phases.

• Proceedings of the KIEE Conference
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• 2005.07b
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• pp.1228-1230
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• 2005

This paper deals with design of heater trigger switching in a persistent current system(PCS) by finite element method(FEM) analysis of YBCO coated conductor(CC) tape. Most promising superconducting wire is YBCO coated conductor tape in these days for its high n value and critical current independency from external magnetic field. It is expected to be used many superconducting application such as fault current limiter and cable etc. The superconducting magnet which is operated in persistent current mode in SMES, NMR, MRI and MAGLEV has many advantages such as a high uniformity of a magnetic field and reducing a thermal loss. A PCS system consists of magnet power supply (MPS) which energized current to a magnet, heater, a coated conductor tape for switching, and superconducting magnet. In this paper, the characteristic of thermal quench of the YBCO CC tape and BSCCO tape by heater trigger analyzed by FEM. And optimal length of heater is calculated by temperature and time analysis. This heater trigger analysis is expected to be a basic concept of PCS application design.

• Journal of Radiation Protection and Research
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• v.2 no.1
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• pp.24-30
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• 1977

Les eaux de $g\'{e}n\'{e}rateur$ de vapeur d'un $r\'{e}acteur$ P. W. R peuvent $\^{e}tre$ $contamin\'{e}es$ par des $radio-\'{e}lements$. Ces eaux sont habituellement $condition\'{e}es$ 'phosphate' pour limiter leur $agressivit\'{e}$ et la tendence actuelle est de remplacer les phosphate par un conditionment 'Amoniaques'. La $pr\'{e}sente$ $\'{e}tude$ a pour but de definir la $possibilit\'{e}$ $d'{\'{e}}purer$ des eaux $condition\'{e}es$ $\'{a}$ l'ammoniaque $\'{a}$ l'aide $d'{\'{e}}changeurs$ d'ion organiques. Des Facteurs de $D\'{e}contamination$ (F. D) en Cesium 137 et Strontium 90 et la $dur\'{e}e$ du cycle $d'{\'{e}}puration$ ont $d\^{u}$ $\^{e}tre$ bien meilleurs avec une colonne de 10 ml de $r\'{e}sine$ Carborylique Duolite $CC_4$ mise sous forme acide, suivie d'une colonne de 10 ml de $r\'{e}sine$ cationique Amberlite IR 120 mise sous forme acide et suivie d'une colonne de 10 ml de $r\'{e}sine$ anionique Amberlite IRA 400 mise sous forme hydroxyde.

• The Journal of Korean Institute of Information Technology
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• v.16 no.12
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• pp.101-107
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• 2018

In wireless sensor network technology, which has been applied to various fields, the power supply and the power management of sensors are the most important issues. For this reason, a new concept of power supply and power management device is required. In this paper, we developed an autonomous independent power supply system that supplies the stable power to a sensor node without an additional external input by applying the energy harvesting technology using the electromagnetic induction principle by utilizing the current flowing in the transmission line. The proposed autonomous independent power supply system consists of a power supply using Power CT and a power management system including a charging circuit. The power management device uses a voltage limiter circuit and a monitoring circuit of charging voltage and current to ensure the safety of charging of the battery. In order to verify the performance of the proposed system, we applied it to the SVL diagnostic system and confirmed that it operates stably.