• Proceedings of the KIEE Conference
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• 2009.07a
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• pp.323_324
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• 2009

345kV Incheon Thermal Power Plant Transmission Line Collapse Analysis and Countermeasures. The Typhoon Galmaegi which had been formed in July 15, 2008 diminished into a tropical cyclone and cooled the air above the West Sea. The cooled air colliding with the warm inland air caused a strong whirlwind at some places in the west seaside; the whirlwind battered the 345kV Incheon Thermal Power Plant Transmission Line to be collapsed. The resistance against wind pressure, one of the key elements in transmission line engineering, is designed to endure the pressure corresponding to the maximum instantaneous wind speed. Before the above accident happened, no transmission line has ever been collapsed by a whirlwind. So this paper is aimed to analyze causes that collapsed 345kV Incheon Thermal Power Plant transmission line and to introduce countermeasures.

• Journal of Korean Society for Atmospheric Environment
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• v.14 no.4
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• pp.321-332
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• 1998

Various meleorologlcal dada obtained by SODAR system in shoreline area surrounding Boryung power plant have been analysed to investigate atmospheric diffusibility. Important conclusion may be summarized as follows; (i) Stability classification scheme based on co (standard deviation of wind direction in degree for averaging time of 1 hour) appears to evaluate certain atmospheric velocity and : indicate horizontal mean wind speed. Thus different scheme for stability classification seems to be preferable in order to appropriately estimate lateral and vertical dispersion coefficients cy and cz, respectively. (ii) As a result of comparisons between 3 available schemes for estimating of mixing height, best one turned out to be the double height scheme where height corresponds to maximum cw.

• Korean Journal of Agricultural and Forest Meteorology
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• v.4 no.4
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• pp.197-202
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• 2002

A new method is used to estimate the amount of water evaporation from Class A Pan with higher precision and accuracy. The principle of method is to detect the weight change of a buoyant sinker resulting from a change in water level of Class A Pan. A strain-gauge load cell is used to measure the weight change. Field observation of evaporation was done at Pohang Meteorological Station from June 24 to August 4, 2002. By using this new method, it is possible to measure hourly evaporation accurately even under a strong solar radiation and wind disturbance, enabling a direct comparison of evaporation with other meteorological elements. At night, under low humidity and high wind speed conditions, more evaporation was recorded than during daytime. Maximum evaporation rates observed during this period exceed 1.0 mm/hour under the sunny and windy conditions with low humidity. To understand relationships between meteorological elements and latent heat flux at ground level, we suggest intensive held experiments using high accuracy evaporation recording instruments with hourly time interval.

• Wind and Structures
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• v.12 no.3
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• pp.281-283
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• 2009

Marquardt method is used to estimate the aerodynamic parameters in urban area of Beijing City, China, including displacement length (d), roughness length ($z_0$) and friction velocity (u*) and drag coefficient. The surface drag coefficient defined as the ratio between friction velocity and mean wind speed is 0.125 in our research, which is close to typical urban area value. The averaged d and $z_0$ are 1.2 m and 7.6 m. d and $z_0$ change with direction because of the surface heterogeneity over urban surface and reach their maximum values at S-SW sector, this tendency agrees with the surface rough element distribution around the observation tower.

• Proceedings of the KSME Conference
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• 2008.11a
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• pp.757-761
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• 2008

The aerostat dynamic equation of motion has been built including the tether cable dynamic effects. A numerical program to solve the derived equation of motion has been developed. The dynamic motion of the 32m aerostat has been analyzed under discrete gust and continuous turbulence. The aerostat behaviors under discrete gust which represents a deterministic approach for determining design loads for manned aircraft are solved to verify the effect of aerostat mechanical properties on the aerostat dynamic behavior. Continuous turbulences are simulated for each given altitude, translational mean wind velocity and gust intensity. Dynamic behaviors of the 32m aerostat are simulated for each continuous turbulence conditions. Translational and vertical velocity and pitching behavior and tether reaction force are monitored for each simulation.

• Journal of the Korean Society of Fisheries and Ocean Technology
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• v.33 no.4
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• pp.360-369
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• 1997

We calculated the residual current forced by buoyancy, wind stress, and tidal stress in the Chinhae Bay using a three-dimensional diagnostic model. The calculated current was also compared with the observation. The flow directs outward from the central area of the Bay in the upper layer, and also forms eddy-shape stucture in the upper and middle layers. The flow of bottom layer shows an opposite pattern compared to those of top and middle layers. The maximum speed was 6.05 em/see (September) and 3.49 cm/sec (November) in the upper layer, and 4.39 cm/sec on both month in the middle layer. The Kinetic energy of November (8.39xlO' W) was larger than that of September (1.24xlO 'W), mainly resulting from larger buoyancy effect in September. In spite of the roughness of the grid size(1 km) and wind date, the calculated flow shows eorrelation(r=0.71) with the observation. We expect that the correlation be increased by increased by adopting the fine grid and the variable coefficients of diffusion and viscosity.

• Advances in aircraft and spacecraft science
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• v.4 no.2
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• pp.125-144
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• 2017

This paper summarises the design of a gust generator and the comparison between high fidelity numerical results and experimental results. The gust generator has been designed for a low subsonic wind tunnel in order to perform gust response experiments on wings and assess load alleviation. Special attention has been given to the different design parameters that influence the shape of the gust velocity profile by means of CFD simulations. Design parameters include frequency of actuation, flow speed, maximum deflection, chord length and gust vane spacing. The numerical results are compared to experimental results obtained using a hot-wire anemometer and flow visualisation by means of a tuft and smoke. The first assessment of the performance of the gust generator showed proper operation of the gust generator across the entire range of interest.

• Journal of Korean Society of Steel Construction
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• v.24 no.1
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• pp.47-58
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• 2012

Dynamic behaviors of a corrugated steel plate tunnel lining system are examined under wind loads due to passing vehicles. Applied wind loads are simulated by applying the time functions as a vehicle moves through the tunnel. Wind loads are described by the pressure and suction as a vehicle arrives and leaves target positions in the tunnel. The tunnel lining is modeled using the simplified shell elements that retain the characteristics of the corrugated shapes. The displacements of the tunnel lining are evaluated under various conditions regarding wind velocity and the passing vehicles. The responses are found to increase as the vehicle velocity and wind velocity increase. A maximum displacement of 25mm occurs when two vehicles are crossing at the speed of 120km/h. A row of vehicles running consecutively minimally affects the dynamic responses with less than 2.5% of the dynamic responses enlarged and attributed to one running vehicle. It should be noted that the dynamic responses of the tunnel lining should be considered when there is no shotcrete applied.

• Journal of Power Electronics
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• v.14 no.2
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• pp.271-281
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• 2014

Fluctuating wind conditions necessitate the use of a variable speed wind turbine (VSWT) with a AC/DC/AC converter scheme in order to harvest the maximum power from the wind and to decouple the synchronous generator voltage and frequency from the grid voltage and frequency. In this paper, a combination of a three phase diode bridge rectifier (DBR) and a modified topology of the diode clamped multilevel inverter (DCMLI) has been considered as an AC/DC/AC converter. A control strategy has been proposed for the DCMLI to achieve the objective of grid interface of a wind power system together with local load compensation. A novel fixed frequency current control method is proposed for the DCMLI based on the level shifted multi carrier PWM for achieving the required control objectives with equal and uniform switching frequency operation for better control and thermal management with the modified DCMLI. The condition of the controller gain is derived to ensure the operation of the DCMLI at the fixed frequency of the carrier. The converter current injected into the distribution grid is controlled in accordance with the wind power availability. In addition, load compensation is performed as an added facility in order to free the source currents being fed from the grid of harmonic distortion, unbalance and a low power factor even though the load may be unbalanced, non-linear and of a poor power factor. The results are validated using PSCAD/EMTDC simulation studies.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.19 no.1
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• pp.109-116
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• 2005

Wind power and photovoltaic(PV) systems are getting into the spotlight as substitute energy. But problem is happened stability by speed change of wind and the power output of the sun's ray. The power output amount according to velocity of wind power system. System breakdown can happen at change of sudden velocity, typhoon and night. This paper shows a automatic tail safety brake controller based on feedback control using wind velocity. The operation of automatic tail safety controller verified by manual test. PV system is a energy change system by temperature of sun's ray and cell. Maximum power point tracking(MPPT) is used in PV systems to maximize the photovoltaic array output power. In existed PV system is low output and changeable DC voltage for boost and filtering the buck-boost converter use. But, this paper established deformed DC-DC converter. Changed Buck-boost converter's unlined output current to line output current using DC-DC converter. This is effect that reduce ripple of output current. Proved through an output waveform comparison experiment. Finally, tail safety brake controller is established to wind turbine system for stability elevation and DC-DC converter is established on PV system for stability output.