• Proceedings of the KIEE Conference
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• 2006.11a
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• pp.151-153
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• 2006

This paper describes the transient phenomena considering transformer model in combined distribution systems with power cables. To evaluate the overvoltage, the change of transformer model and system structure are considered. Transformer parameters calculated by BCTRAN of EMTP are considered to evaluate surge generation in underground distribution systems when underground distribution system has various parameters. It is evaluated that overvoltage value increases and decreases according to the structure of system. However it is confirmed that there is not much effect to overvoltage as transformer is operated in distribution line.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2010.06a
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• pp.203-203
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• 2010

The proton exchange membrane fuel cell (PEMFC) is different from the normal power supply, and it is a nonlinear, multi-input, strong coupling, the complex dynamic system with large time delay. At present, many studies on the content of the fuel cell fuel cells focus on a static process, this paper analyzed in subsequent sections of the process of fuel cell dynamic response time of transition, and then it found the method to reduce the response time during the process of load change to ensure that the stability of output power.

• Proceedings of the KIEE Conference
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• 1999.07e
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• pp.2069-2072
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• 1999

The extended 765 kV system may have severe electrical transients according to the interconnection of transmission lines and have long transmission line over 250 km. So we need to analyze the transient phenomena to confirm the insulation coordination which is designed for 765 kV project step I. In particular, this paper shows the analysis results of secondary arc extinction by HSGS (high speed ground switch) application. The EMTP/MODELS were used to simulation study of secondary arc phenomena. We had confirmed the TRV(transient recovery voltage) and rated current of HSGS which will be used in the KEPCO 765 kV system.

• Journal of the Korean Institute of Telematics and Electronics
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• v.7 no.4
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• pp.14-19
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• 1970

Transient phenomena in the p-n junction due to the selfheating effect of microplasma current have been investigated for the cases of small current and of large current. For the small current case, the temperature rise of the microplasma site is proportional to the current decrease and a unique time constant could be defined. However, the situation was complicated for the case of large current, and the time constant was not uniquely defined.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.59 no.7
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• pp.1276-1281
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• 2010

To analyze the gas discharge phenomena in parallel-plane electrodes, the fully coupled finite element method (FEM) considering secondary electron emission effects in discharge column was adopted in this paper. Two coupled equations of the hydrodynamic diffusion-drift equations for three carriers and the Poisson's equation for electric scalar potential should be solved as a system equation. The proposed method including two secondary electron processes of the photoemission and background ionization has been successfully applied to evaluating the breakdown voltage in parallel-plane electrodes and is verified by comparing its numerical results with the experimental ones. From the obtained results, it is inferred that the proposed numerical scheme will be useful for predicting and understanding streamer transient phenomena.

• Proceedings of the KIEE Conference
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• 2000.07b
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• pp.644-646
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• 2000

An induction motor can be controlled like a separately excited do motor by field oriented control(or vector control). In vector control, Because the transformation of the stator's 3-phase current into two orthogonal current is required. the control scheme is complicated. But, Yamamura proposed a field acceleration method(FAM) without the phase transformation. FAM simplify an implementation control scheme for induction motors. In this paper, the analysis of transient phenomena of a squirrel-cage induction motor was achieved by the spiral vector method and the phase segregation method. It simplified control schemes more than those of vector control.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 1997.11a
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• pp.480-483
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• 1997

This paper describes dielectric characteristics and discharge development mechanisms of SF$_{6}$ gas stressed by very fast transient overvoltages in inhomogeneous electric field. Predischarge phenomena of SF$_{6}$ gas in non-uniform fields are statistically investigated with positive and negative very fast trannsient overvoltages. It was confirmed that all of the predischarges of the positive and negative polarities develop in a regime of stepwise leader extension. i.e, the predischarge developments leading to breakdown against very fast transient overvoltages are similar to the non-oscillating impulse voltages.ges.

• Journal of the Institute of Electronics Engineers of Korea SD
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• v.38 no.1
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• pp.1-12
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• 2001

Based on mixed-mode transient analyses utilizing a 2-dimensional device simulator, we have suggested the methodology to analyze the HBM ESD phenomena in CMOS chips utilizing NMOS transistors for ESD protection, and have analyzes the HBM discharge mechanisms in detail. Also the second breakdown characteristics in the protection device have been successfully simulated based on mixed-mode simulations, to explain the discharge mechanisms leading to device failure. To analyze the effects of the device structure changes on the discharge characteristics, we have compared the results of DC analyses and mixed-mode transient analyses, and have discussed about more robust designs of NMOS transistor structures against HBM ESD based on the analyses.

• Nuclear Engineering and Technology
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• v.49 no.3
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• pp.466-475
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• 2017

Coolant mixing under natural circulation flow regime constitutes a key parameter that may play a role in the course of an accidental transient in a nuclear pressurized water reactor. This issue has motivated some experimental investigations carried out within the OECD/NEA PKL projects. The aim was to assess the coolant mixing phenomenon in the reactor pressure vessel downcomer and the core lower plenum under several asymmetric steady and unsteady flow conditions, and to provide experimental data for code validations. Former studies addressed the mixing phenomenon using, on the one hand, one-dimensional computational approaches with cross flows that are not fully validated under transient conditions and, on the other hand, expensive computational fluid dynamic tools that are not always justified for large-scale macroscopic phenomena. In the current framework, an unsteady coolant mixing experiment carried out in the Rossendorf coolant mixing test facility is simulated using the three-dimensional porous media capabilities of the thermal-hydraulic system CATHARE code. The current study allows highlighting the current capabilities of these codes and their suitability for reproducing the main phenomena occurring during asymmetric transient natural circulation mixing conditions.

• The Proceedings of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.11 no.3
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• pp.88-96
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• 1997

This paper analyzes the transients for parameters on electrical distribution system. We analyze the voltage sag and switching surge caused by reclosing and develope a distribution system model of multiground type using a practical data of 22.9(kV) distribution system. It is at customer that we analyze an affecting of reclosing through EMTP (Electromagnetic Transients Program) simulation, present transient phenomena on fault line and parallel line. Also. we analyze the various parameters affecting this phenomena in detail through parametric analysis. These factors include the fault location, load size, load power factor, capacitor bank size, and reclosing angle. And relation between these parameters and transient phenomena is presented.