• Journal of Mechanical Science and Technology
• /
• v.18 no.9
• /
• pp.1614-1622
• /
• 2004

When a High Speed Train (HST) passes through a station with no stop, effects of wind pressure transients caused by this passing train have to be considered for the safety of passengers on the platform and for the possible structural safety problems as well. In Gwangmyeong and Daejeon stations of the Korean high speed railroad, tunnels inside stations for the passing train are proposed to reduce the noise and wind pressure transients to the passengers on the platform. In the present study, transient 3-D full Navier-Stokes solutions with moving mesh to implement train movement are obtained and compared with the results obtained by the towing tank experiment. Investigations on flow phenomena for various train speeds and design modifications are also performed.

• The Transactions of the Korean Institute of Power Electronics
• /
• v.6 no.3
• /
• pp.291-298
• /
• 2001

This paper deals with a full functional simulation of UPFC (Unified Power Flow Controller) which is a next generation FACTS (Flexible AC Transmission Systems) technology. Through analysis and modeling of he UPFC, power flow control is simulated. Active and reactive power controls, and input side bus voltage control are performed by EMTDC (Electro-Magnetic Transients in DC systems) which is a general purpose time domain simulation program for simulating power systems transients and its controls. Dynamic performances of the UPFC are verified by simulation results.

• 제어로봇시스템학회:학술대회논문집
• /
• 2005.06a
• /
• pp.800-804
• /
• 2005

Load flow and short circuit fault transients of a power distribution system with wind turbines as dispersed generation units is presented. Usage of renewable energies such as wind is already a small part of total installed power system in medium and low voltage networks. In this paper, a radial power distribution system with wind turbines is simulated using DIgSILENT PowerFactory software for their influence on load flow and short circuit fault transients. Short fault occurring in dispersed generation systems causes some problems for the system and costumers such as fault level increase or the problems of sudden fluctuations in the current, voltage, power and torque of the double fed induction machine utilized in the wind turbines which have been studied and investigated.

• International Journal of Fluid Machinery and Systems
• /
• v.8 no.2
• /
• pp.63-72
• /
• 2015

Water hammer phenomena are important issues for the design and the operation of hydro power plants. Especially, if several reversible pump-turbines are coupled hydraulically there may be strong unit interactions. The precise prediction of all relevant transients is challenging. Regarding a recent pump-storage project, dynamic measurements motivate an improved turbine modeling approach making use of a Thoma number dependency. The proposed method is validated for several transient scenarios and turns out to improve correlation between measurement and simulation results significantly. Starting from simple scenarios, this allows better prediction of more complex transients. By applying a fully automated simulation procedure broad operating ranges of the highly nonlinear system can be covered providing a consistent insight into the plant dynamics. This finally allows the optimization of the closing strategy and hence the overall power plant performance.

• Proceedings of the IEEK Conference
• /
• 1999.11a
• /
• pp.216-219
• /
• 1999

A simple two-terminal cyclic current-voltage(I-V) technique is used to measure the current-transients in MOS capacitors. Distinct charging/discharging currents were measured and analyzed as a function of (1) the hold time. (2) the gate polarity during the FNT electron injection, (3) the injection fluence and (4) the annealing time after the injection had stopped. Discharging and charging current-transients were strongly dependent upon the conditions for forming the inversion layer and the density of interface traps caused during the FNT electron injection, respectively. Several tentative mechanisms were suggested in the current work.

• Fire Science and Engineering
• /
• v.11 no.4
• /
• pp.25-31
• /
• 1997

In this study, EMTP(Electromagnetic Transients Program) which is one of the most well-known computer simulation methods is used to collect the data for a power plant fault. EMTP is the program for an interpretation of the phenomena of electric transients, and is designed to manifest the data of the electric current and voltage etc. at the time of a power plant fault. By EMTP, I analyze the properties of the heat energy which are transferred from the electrics when a power plant fault brings out. In terms of the results of this study, it is able to measure the heat energy at a power plant fault (power transformer) and to be acquired of the related data. And moreover, these data are expected to be used as a standard for the protection of the fire owing to a high voltage power transformer fault.

• The Bulletin of The Korean Astronomical Society
• /
• v.42 no.1
• /
• pp.44.3-44.3
• /
• 2017

We introduce sample light curves of optical transients discovered by the KMTNet Supernoa Program, focusing on their early discoveries and rapid evolutions decoded in the high-cadence observations of the program. For some sources, we also show their spectra obtained either from rapid Target-of-Opportunity follow-up observations immediately after their discoveries or from regularly-scheduled observations. We expect the program to bring unprecedented insights into what is happening during early phases of various types of optical transients, centered on supernovae.

• The Transactions of the Korean Institute of Electrical Engineers P
• /
• v.65 no.2
• /
• pp.122-129
• /
• 2016

Current differential protection relaying with second harmonic restraint is the main protection for large capacity power transformer. PSCAD simulation program is widely used for modeling of dynamic varying transients phenomena. This paper deals with a power transformer model and transients analysis using PSCAD software to develop IED for power transformer. Simulation was carried out using a three phase 40MVA, 154/22.9kV, 60Hz, two-winding transformer with Y-Y connection used in actual fields. The paper analyzed transformer magnetizing inrush, external fault, and internal fault conditions with this model in the time domain. In addition, we performed an analysis in the frequency domain using FFT during several conditions.

• Proceedings of the KIEE Conference
• /
• 1990.07a
• /
• pp.297-300
• /
• 1990

The measurement of very fast transients generated by disconnecting switches in gas-insulated switchgear(GIS) have to deal with the problems such as reliability, interference pich-up, optimal design of high voitage equipments. This paper presents a new developed voltage sensor to measure the very fast transients, the basic theory of the measuring method, the design, structure of planar capacitive voltage probe are described. Finally the examples of modelling tests on an actual site GIS are discussed.

• Proceedings of the Korea Society of Environmental Biology Conference
• /
• 2002.11a
• /
• pp.127-131
• /
• 2002

The OJIP transients were investigated from leaves of Crinum asiaticum var. japonicum, Osmanthus insularis, Chloranthus glaber and Asplenium antiquum, in order to screen the indicators for quantification of environmental stresses and to apply them to the plant vitality test. The obvious diurnal changes or OJIP transients were found in Crinum asiaticum var. japonicum, Osmanthus insularis growing in sunny habitats, showing lower Fp and higher Fo in day time. The values of SF $I_{no}$ and P $I_{NO}$ increased dramatically in day time in leaves of Crinum asiaticum var. japonicum, Osmanthus insularis, and Asplenium antiquum. Although the value of RC/CS decreased slightly in day time in leaves of 4 tropica $l_tropical plants, the obvious diurnal changes or OJIP transients were not seen in winter, suggesting that tropica $l_tropical paints used in this research seemed to be irreversibly damaged in winter. However, the values of ETo/RC and Ψo/(1-Ψo) increased significantly in leaves of Crinum asiaticum var. japonicum, indicating that ETO/RC and Ψo/(1-Ψo) were useful as indicator parameters for scensing of low temperature.ature.