• Proceedings of the KIEE Conference
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• 2001.04a
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• pp.44-46
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• 2001

This paper describes the use of the PHOENICS CFD package for the simulation of the high-current period of the arcing process in a hybrid rotating arc/auto expansion by interrupter. The operating principle of this device depends on rapid arc rotation due to the magnetic field created by the fault current through a coil which is mounted on contacts and also relies on the principle of thermal expansion created by arc energy in extinguishing chamber and finally causes pressure rise in expansion volume. This paper is divided into three main sections. The first gives a brief overview of the interrupter. The second section gives a full description of the methods used in the calculation. The final section presents some sample results for the hybrid interrupter.

• Proceedings of the KIEE Conference
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• 1994.07b
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• pp.1661-1664
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• 1994

In designing $SF_6$ puffer circuit breakers, analyzing are behavior during current zero region and thermal recovery characteristics after current interrupt ion is very important. In this paper, a mathematical are model based on the integral method has been based to analyze them. The pressure rise in the puffer chamber and the distributions of pressure, density, velocity and enthalpy inside nozzle are calculated and analyzed at current zero region. The influence of fault current magnitude and change of di/dt at current zero on the interruption capability of puffer circuit breakers is investigated. Finally, the calculated results are compared with the available results from experiment.

• Proceedings of the KIEE Conference
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• 2000.07b
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• pp.1374-1376
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• 2000

In this paper, sample coils for stator form-wound winding of traction motor were tested by the accelerative thermal degradation, which composed of heat, vibration, moisture and overvoltage applying. Reliability and expected life were evaluated on the insulation system for 200 class traction motor. After aging of 10 cycles, insulation resistance and PI properties were investigated as diagnosis tests in the range of $20{\sim}160^{\circ}C$. Analysis of polarization properties was performed on the base of do current-time change.

• Progress in Superconductivity and Cryogenics
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• v.21 no.4
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• pp.44-47
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• 2019

This paper is a study of recovery under load process of superconducting fault current limiter (SFCL). SFCL consists of five parallel-connected high-temperature superconductor (HTS) tapes additionally stabilized by stainless tape. Previously, HTS was heated by current pulse to simulate a short circuit in a power grid. During the cooling period, the current amplitude decreased to 23% or less of HTS critical current value, which is the simulation of network re-switching. When HTS with a polymer coating is cooled, temperature gradient on thermal insulation layer occurs, that prevents a boiling crisis and improves the heat sink into liquid nitrogen. Two samples are coated with a 30 ㎛ and 50 ㎛ polylactide (PLA) layers, reference sample has no polymer coating on it. Samples with a polymer coating show 3-5 times faster cooling than the reference one.

• Journal of the Korean Society for Railway
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• v.5 no.2
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• pp.125-132
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• 2002

As the public use part of the railway and the road, the railway crossing is important to work properly by two transportation means. Also, It is important to provide the good face of friction on the railway crossing in aspect of protecting the railway crossing accident. Lately, the material of railway crossing panel is the wood, the asphalt, and the steel. As they have a various fault, it was studied to analyze the structural action of the new material, rubber panel. This paper analyzed eigenvalue, stress and displacement by truck passing weight, thermal stress and train moving weight, using the Finite Element Method model

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.15 no.1
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• pp.93-101
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• 2002

In this study, the stator form-winding sample coils based on silicone resin and polyimide were made for fault prediction and reliability estimation on the C-Class(200$\^{C}$ ) insulation system of traction motors. The complex accelerative degradation was periodically performed during 10 cycles, which was composed of thermal stress, fast rising surge voltage, vibration, water immersion and overvoltage applying. After aging of 10 cycles, the condition diagnosis test such as insulation resistance '||'&'||' polarization index, capacitance '||'&'||' dielectric loss and partial discharge properties were investigated in the temperature range of 20 ∼ 160$\^{C}$. Relationship among condition diagnosis tests was analyzed to find a dominative degradation factor and an insulation state at end-life point.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.60 no.4
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• pp.700-704
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• 2011

This paper proposes a coordinative protection study results of 22.9kV HTS(High-Temperature Superconducting) cable implemented distribution system. HTS cable can provide about 5 times larger transfer capacability compare to conventional XLPE cable, however, it has different heat characteristic so called quench. This paper presents the simulation results on Ichun substation HTS cable which connects main transformer and 22.9kV bus. Various expected fault cases are considered and discussed to examine whether conventional protection scheme is effective to protect both of existing facilities and HTS cable. With the results of simulation, conventional protection scheme can be used if instantaneous element and time inverse elements could be adjusted with proper time coordination. Internal temperatures of HTS cable conductor in safe region with proper protection without quench. This results are to be demonstrated by the field test and will be implemented in Ichon substation HTS cable protection and control system.

• Proceedings of the KIEE Conference
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• 2001.07d
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• pp.2108-2110
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• 2001

Used analog control systems have been converted into digital control systems due to performance degradation and difficulty of maintenance. There are few domestic DCS (Distribued Control System)s that have been applied to power plant. To apply a domestic DCS to power plant, the reliability, redundacny, and fault tolerance of DCS is important. Besides those items, the control action of control function block is also important. In this paper, we describe the requirements that PID control function block has to have, and implement a PID control function block that satisfies those requirements. Finally, real control result using an implemented PID function block in thermal power plant shows the validity of an implemented PID control function block.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.32 no.4
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• pp.101-110
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• 2004

Flight and Qualification Models of Single Board Computer (SBC), called On-Board Computer (OBC), for HAUSAT-l picosatellite, which is scheduled to launch on September, 2004 by Russian "Dnepr" launch vehicle, have been developed. The OBC of HAUSAT-1 has been designed with some improved features compared to other picosatellites. A multifunctional controller and up-to-date SPI (Serial Peripheral Interface) and 1-Wire interface are implemented to simplify the harness routing and to minimize the mass and size of OBC. The improved fault-tolerant architecture design methodology is incorporated in the HAUSAT-1 OBC to protect against space radiation environment. The functions of the OBC were fully tested and verified by the Electrical Test Bed (ETB) model. This paper is also addressing the environmental test results, such as random vibration and thermal vacuum tests.

• Journal of the Korean Vacuum Society
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• v.7 no.1
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• pp.35-42
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• 1998

- The Si-$SiO_2$ interface of silicon on insulator (SOI) formed by 100 keV $O^+$ was ohserved using high resolution transmission electron microscopy (HRTEM), before and after annealing. The interface of as-implanted sample, ~$5\times 10^{17}\textrm{cm}^{-2}O^+$ implanted at $550^{\circ}C$ was very rough and it has many defectsoxide precipitate, stacking fault, coesite $SiO_2$ etc. However, the interface became flat by high temperature annealing at $1300^{\circ}C$ for 4 hour. It's roughness, observed by HRTEM, was comparable to the interface roughness of 3 keV $O_2^\;+$ ion beam oxide and -6 nm gate oxide formed by thermal oxidation.