• The Transactions of the Korean Institute of Electrical Engineers A
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• v.48 no.11
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• pp.1410-1416
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• 1999

This paper aims at investigating the operating-mode characteristics of two-module Thyristor Controlled Series Compensator (TCSC) as an equivalent of the multi-module TCSC in a simple three-phase power transmission system. The load flow program is developed to analyze the steady-state characteristics of two-module TCSC system and to find the thyristor firing angles for the required real power flow. The stability calculation program is developed with Poincare mapping theory. Simulation studies of the TCSC power transmission system using EMTP are performed to evaluate the transient characteristics of two-module TCSC as a real power flow controller and to rpove the results of the load flow calculation and the stability analysis. In the process of the study, the operating-mode characteristics of two-module TCSC are evaluated and compared to those of single-module TCSC.

• Journal of the Korean Society for Precision Engineering
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• v.11 no.2
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• pp.65-74
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• 1994

Backcap is an electric remote control system for the operation of directional flow control valves. This paper presents a new type of basckcap system which is characterized by its simple construction. The backcap is essentially a hydraulic cylinder of which the piston is connected to a spool of hydraulic valve and controlled by input current. An inherent feedback is imposed on its mechanism so that no artificial noe is needed. Characteristics of the backcap is verified by stability analysis, transient motion and steady state positioning for step inputs. Design parameter analyses have been executer by some analytical approaches and computer simulations, which lead to their optimal valves. These results contributed to an effective new backcap system and its design strategy.

• Journal of the Korean Society of Safety
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• v.36 no.3
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• pp.74-80
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• 2021

Korea Atomic Energy Research Institute (KAERI) has been operating an integral effects test facility, the Advanced Thermal-Hydraulic Test Loop for Accident Simulation (ATLAS), according to APR1400 for transient experimental and design basis accident simulation. Moreover, based on the experimental data, the domestic standard problem (DSP) program has been conducted in Korea to validate system codes. Recently, through DSP-05, the performance of the passive auxiliary feedwater system (PAFS) in the event of multiple steam generator tube rupture (MSGTR) has been analyzed. However, some errors exist in the reference input model distributed for DSP-05. Furthermore, the calculation results of the heat loss correlation for the secondary system presented in the technical report of the reference indicate that a large difference is present in heat loss from the target value. Thus, in this study, the reference model is corrected using the geometric information from the design report and drawings of ATLAS. Additionally, a new heat loss correlation is suggested by fitting the results of the heat loss tests. Herein, MSGTR-PAFS accident analysis is performed using MARS-KS 1.5 with the improved model. The steady-state calculation results do not significantly differ from the experimental values, and the overall physical behavior of the transient state is properly predicted. Particularly, the predicted operating time of PAFS is similar to the experimental results obtained by the modified model. Furthermore, the operating time of PAFS varies according to the heat loss of the secondary system, and the sensitivity analysis results for the heat loss of the secondary system are presented.

• 한국신재생에너지학회:학술대회논문집
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• 2007.06a
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• pp.5-8
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• 2007

In this paper, numerical investigation has been carried out to study performance of methane autothermal reformer and dynamic behavior for light-off under various operating conditions. In order to simulate the given problems, numerical methods are incorporated using finite-volume method. In addition, porous medium approach is accepted because the catalytic phenomena occur in porous media. Also, start-up issue is significant in autothermal reformer although the reaction is marginally exothermic. Thus, in this study transient behavior has been also investigated to find out optimal operating conditions for start-up.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.10 no.3
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• pp.260-270
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• 1998

The viscous plane stagnation-flow solidification problem is theoretically investigated. An analytic solution at the beginning of solidification is obtained by expanding the temperature and thickness of solidified layer in powers of time. An exact expression for the steady-state thickness of solidified layer is also obtained. The .fluid flow toward the cold substrate inhibits the solidification process. As Stefan number becomes larger, or Prandtl number becomes smaller, the solidification is more strongly inhibited by the fluid flow. The transient heat flux at the liquid side of solid-liquid interface is increased, as Stefan number or Prandtl number is increased.

• The Journal of Engineering Geology
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• v.3 no.2
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• pp.149-165
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• 1993

Nowadays, the field hydraulic test is still an only method to evaluate groundwater characteristics in subsurface. The results of hydraulic test are very important for the concept model of fracture hydrogeology as well as the geometric pattern of fractures. The hydraulic tests performed in Korea are generally analysed under such assumption as steady radial flow in homogeneous aquifer or along simple geometry of fractures. Also the transmissivity measured in a fixed interval length is equivalent to a sum of individual fracture transmissivities in test legth. The boundary effects of weH hydraulics and the geometry of flow paths are hardly obtained from the test results analysed by a steady flow method. To circumvent this problem, the flow dimensional analysis was attempted from the results of constant pressure injection test carried out in a fractured granite area. A comparison of the hydraulic conductivity values from the transient and steady analysis shows that the latter is about a factor of 2~3 higher than the former. However, it was possible to analyse a flow dimension of each test interval from flow rate variation with time. The upper part of the bedrock(<10m deep) indicates an open boundary and the flow dimension shows nearly steady states, while the lower part of the bedrock(>25m deep) is characterized as sublinear flow dimension with a dosed boundary. In one of the test sections(15m deep), the flow dimension was changed from linear flow to spherical flow. From the experience of this study, one of the immediate problems to be solved is to enhance the field testing equipments, i.e., an accurate flowmeter with autorecording and a pressure detecting device to be able to install in the test section.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2001.11b
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• pp.205-208
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• 2001

Steady state and transient thermal analysis has been done by a finite element method in a diode of 12kV blocking voltage for microwave oven. The diode was fabricated by soldering ten pieces of 1200V diodes in series, capping a dummy wafer at the far end of diode series, and finally copper wire bonded for building anode and cathode terminal. In order to achieve high voltage and reliability, the edge of each diode was beveled and passivated by resin and epoxy with a thickness of $25{\mu}m$ and $3700{\mu}m$, respectively. The chip size, thickness and material properties were very important factor for high voltage diode package. And also, thermal stress value was highest in the edge of diode and solder. So, design of edge in silicon was very important to thermal stress.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2001.11a
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• pp.205-208
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• 2001

Steady state and transient thermal analysis has been done by a finite element method in a diode of 12kV blocking voltage for microwave oven. The diode was fabricated by soldering ten pieces of 1200V diodes in series, capping a dummy wafer at the far end of diode series, and finally copper wire bonded for building anode and cathode terminal. In order to achieve high voltage and reliability, the edge of each diode was beveled and passivated by resin and epoxy with a thickness of 25$\mu\textrm{m}$ and 3,700$\mu\textrm{m}$, respectively. The chip size, thickness and material properties were very important factor for high voltage diode package. And also, thermal stress value was highest in the edge of diode and solder. So, design of edge in silicon was very important to thermal stress.

• Journal of the Korean Society of Propulsion Engineers
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• v.8 no.3
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• pp.27-36
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• 2004

This paper has been conducted to design for pressure regulation system. to simulate for performance of turbo pump unit using AMESim(Advanced Modeling Environment for Simulation of Engineering Systems). With optimized of system, pressure regulation system has been confirmed dynamic characteristics of transient and steady states range based on static modeling of open type turbo pump fed engine system. These results can be utilized to verify for performance test facility of propulsion control system for analysis on control valves, review of the fundamental principle on the control logic and certificating engine feeding system.

• Proceedings of the KIEE Conference
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• 2011.07a
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• pp.523-524
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• 2011

This paper covers induced voltage in parallel telecommunication cable with underground power cable to be linked between substations. The simulation was carried out the induced voltage in telecommunication cable according to the transposition of power cables and fault location for various conditions. This study based on the EMTP/ATPDraw with actual underground cable systems while the power cables are in steady state and transient state.