• 제목/요약/키워드: wind variation

검색결과 855건 처리시간 0.035초

Capacity of a transmission tower under downburst wind loading

  • Mara, T.G.;Hong, H.P.;Lee, C.S.;Ho, T.C.E.
    • Wind and Structures
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    • 제22권1호
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    • pp.65-87
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    • 2016
  • The wind velocity profile over the height of a structure in high intensity wind (HIW) events, such as downbursts, differs from that associated with atmospheric boundary layer (ABL) winds. Current design codes for lattice transmission structures contain only limited advice on the treatment of HIW effects, and structural design is carried out using wind load profiles and response factors derived for ABL winds. The present study assesses the load-deformation curve (capacity curve) of a transmission tower under modeled downburst wind loading, and compares it with that obtained for an ABL wind loading profile. The analysis considers nonlinear inelastic response under simulated downburst wind fields. The capacity curve is represented using the relationship between the base shear and the maximum tip displacement. The results indicate that the capacity curve remains relatively consistent between different downburst scenarios and an ABL loading profile. The use of the capacity curve avoids the difficulty associated with defining a reference wind speed and corresponding wind profile that are adequate and applicable for downburst and ABL winds, thereby allowing a direct comparison of response under synoptic and downburst events. Uncertainty propagation analysis is carried out to evaluate the tower capacity by considering the uncertainty in material properties and geometric variables. The results indicated the coefficient of variation of the tower capacity is small compared to those associated with extreme wind speeds.

Vertical Profiles of Meteorological Parameters over Taegu City

  • Ahn, Byung-Ho;Kwak, Young-Sil
    • International Union of Geodesy and Geophysics Korean Journal of Geophysical Research
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    • 제22권1호
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    • pp.24-32
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    • 1994
  • A special upper-air observation including airsonde and pibal observations was performed to investigate the characteristics features of the vertical distribution of the meteorological elements over Taegu on a selected clear day of each season from October 1991 to August 1992. The diurnal and seasonal variations of the vertical profiles of air temperature and mixing ratio were obtained from airsonde observations and wind speed and direction from pibal observations. The results of these special upper-air observations are as follow : The diurnal variation of the vertical distribution of air temperature reveals the characteristic features associated with the atmospheric boundary layer. All case days, except for the summer season, show upper-level inversion layer which influenced by surface high, and surface inversion layer produced by radiative cooling. The diurnal variation of mixing ratio shows the maximum vale at 1500 LST in both the upper and low levels, and is larger on the lower level than the upper level. The mixing ratio of the lower level is larger than that of the upper level. On the average the mixing ratio decrease with the height, and is the wettest on the summer case day and the driest on the winter case day. The diurnal variation of the wind velocity and direction are variable in the lower level with time and height, while they are steady in the upper level. On the average, the wind direction is southerly or southeasterly for the summer case day, westerly or northwesterly for the spring and fall case days, and northerly or northwesterly for the winter case day.

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Wireless structural health monitoring of stay cables under two consecutive typhoons

  • Kim, Jeong-Tae;Huynh, Thanh-Canh;Lee, So-Young
    • Structural Monitoring and Maintenance
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    • 제1권1호
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    • pp.47-67
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    • 2014
  • This study has been motivated to examine the performance of a wireless sensor system under the typhoons as well as to analyze the effect of the typhoons on the bridge's vibration responses and the variation of cable forces. During the long-term field experiment on a real cable-stayed bridge in years 2011-2012, the bridge had experienced two consecutive typhoons, Bolaven and Tembin, and the wireless sensor system had recorded data of wind speeds and vibration responses from a few survived sensor nodes. In this paper, the wireless structural health monitoring of stay cables under the two consecutive typhoons is presented. Firstly, the wireless monitoring system for cable-stayed bridge is described. Multi-scale vibration sensor nodes are utilized to measure both acceleration and PZT dynamic strain from stay cables. Also, cable forces are estimated by a tension force monitoring software based on vibration properties. Secondly, the cable-stayed bridge with the wireless monitoring system is described and its wireless monitoring capacities for deck and cables are evaluated. Finally, the structural health monitoring of stay cables under the attack of the two typhoons is described. Wind-induced deck vibration, cable vibration and cable force variation are examined based on the field measurements in the cable-stayed bridge under the two consecutive typhoons.

기상조건에 따른 부산지역 대기오염물질 농도변화와 예측에 관한 연구 (On the Prediction and Variation of Air Pollutants Concentration in Relation to the Meteorological Condition in Pusan Area)

  • 정영진;이동인
    • 한국대기환경학회지
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    • 제14권3호
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    • pp.177-190
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    • 1998
  • The concentrations of air pollutants In large cities such as Pusan area have been increased every year due to the increasing of fuels consumption at factories and by vehicles as well as the gravitation of the population. In addition to the pollution sources, time and spatial variation of air pollutants concentration and meteorological factors have a great influence on the air pollution problem. Especially , its concentration is governed by wind direction, wind speed, precipitation, solar radiation, temperature, humidity and cloud amounts, etc. In this study, we have analyzed various data of meteorological factors using typical patterns of the air pressure to investigate how the concentration of air pollutants is varied with meteorological condition. Using the relationship between meteorological factors (air temperature, relative humidity, wind speed and solar radiation) and the concentration of air pollutants (SO2, O3) , experimental prediction formulas for their concentration were obtained. Therefore, these prediction formulas at each meteorological factor in a pressure pattern may be roughly used to predict the air pollutants concentration and contributed to estimate the variation of its value according to the weather condition in Pusan city.

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풍향에 따른 고효율 갠트리 크레인의 안정성에 관한 연구 (A Study on Stability of the Container Crain with respect to the Direction of wind Load)

  • 권순규;한근조;심재준;한동섭;이성욱
    • 한국정밀공학회:학술대회논문집
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    • 한국정밀공학회 2005년도 춘계학술대회 논문집
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    • pp.1984-1987
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    • 2005
  • This study evaluate the statical stability of the container crane with respect to the direction of wind load which is varied between $0^{\circ}$ and $180^{\circ}$ and its average velocity is 40m/s. Using wind experimental data and a formula of wind pressure, we figured out the wind load needed to perform a finite element analysis. And we can obtain the variation of reaction forces at each supporting point according to the direction of wind load.

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PSCAD를 이용한 DFIG풍력발전 최대출력 풍력발전 제어방법에 관한 연구 (Simulation Study on Capturing Maximum Wind Power Control Method of DFIG based on PSCAD/EMTDC)

  • 손계도;최준호;박성준;남순열
    • 대한전기학회:학술대회논문집
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    • 대한전기학회 2009년도 제40회 하계학술대회
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    • pp.1122_1123
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    • 2009
  • Doubly Fed Induction Generator (DFIG) used in variable speed constant frequency wind energy generation system can capture wind energy with the highest efficiency by using the stator flux oriented vector control method. This paper sets up a DFIG modeling of wind generation system in PSCAD/EMTDC to simulate the operational performance with wind speed variation. In order to achieve the characteristics of the maximum utilization of wind power, this paper uses the vector control technology to track largest wind power and the independent control of generator active and reactive power.

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Reliability of microwave towers against extreme winds

  • Deoliya, Rajesh;Datta, T.K.
    • Structural Engineering and Mechanics
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    • 제6권5호
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    • pp.555-569
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    • 1998
  • The reliability of antenna tower designed for a n-year design wind speed is determined by considering the variability of the strength of the component members and of the mean wind speed. For obtaining the n-year design wind speed, maximum annual wind speed is assumed to follow Gumbel Type-1 distribution. Following this distribution of the wind speed, the mean and standard deviation of stresses in each component member are worked out. The variability of the strength of members is defined by means of the nominal strength and a coefficient of variation. The probability of failure of the critical members of tower is determined by the first order second moment method (FOSM) of reliability analysis. Using the above method, the reliability against allowable stress failure of the critical members as well as the system reliabilities for a 75 m tall antenna tower, designed for n-year design wind speed, are presented.

풍속 변화에 따른 발전기 온도 및 전력변환장치 효율에 관한 연구 (A Study on Generator Temperature and Power Converter Efficiency according to change of Wind Velocity)

  • 송영상;한운기;정진수;임현성;조성구;전태현
    • 조명전기설비학회논문지
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    • 제29권7호
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    • pp.8-13
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    • 2015
  • Recently, because a renewable power source must operate as a constant rate in accordance with RPS(Renewable Portfolio Standard), the study of the renewable power sources has been ongoing. Especially because of noise of wind turbine, troubleshooting, and urban greening business, research related with small wind turbine are underway. The economics and reliability are important parts for the activation of small wind turbine, such as solar energy. In this paper, by analyzing the temperature variations for each location and efficiency of power conversion devices in accordance with short period wind speed changes in simulation test, we reviewed the safety about temperature variations of wind generator and the method of selection of power converter.

간략화한 다개상태 모델을 갖는 풍력발전계통을 고려한 전력계통의 신뢰도평가에 관한 기초연구 (A Study on the Probabilistic Reliability Evaluation of Power System Considering Wind Turbine Generators with A simplified Multi-state Model)

  • 오량;박정제;최재석
    • 대한전기학회:학술대회논문집
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    • 대한전기학회 2008년도 제39회 하계학술대회
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    • pp.271-272
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    • 2008
  • Renewable energy resources such as wind, wave, solar, micro hydro, tidal and biomass etc are becoming important stage by stage, considering the effect of environment. Wind energy is one of the most successful sources of renewable energy for the production of electrical energy. What's more, due to wind speed random variation the wind turbine generators can not make two-state model as conventional generators. The method of obtaining reliability evaluation indices of wind turbine generators is different from the conventional generators. This paper presents a study on the reliability evaluation of power system considering wind turbine generators with a simplified multi-state model.

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An Airborne Cycloidal Wind Turbine Mounted Using a Tethered Balloon

  • Hwang, In-Seong;Kang, Wang-Gu;Kim, Seung-Jo
    • International Journal of Aeronautical and Space Sciences
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    • 제12권4호
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    • pp.354-359
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    • 2011
  • This study proposes a design for an airborne wind turbine generator. The proposed system comprises a cycloidal wind turbine adopting a cycloidal rotor blade system that is used at a high altitude. The turbine is mounted on a tethered balloon. The proposed system is relatively easier to be realized and stable. Moreover, the rotor efficiency is high, which can be adjusted using the blade pitch angle variation. In addition, the rotor is well adapted to the wind-flow direction change. This article proves the feasibility of the proposed system through a sample design for a wind turbine that produces a power of 30 kW. The generated wind power at 500 m height is nearly 3 times of that on the ground.