scholarly journals Theoretical Analysis and Experimental Validation on Galloping of Iced Transmission Lines in a Moderating Airflow

2021 ◽  
Vol 2021 ◽  
pp. 1-12
Author(s):  
Bing Huo ◽  
Xuliang Li ◽  
Fujiang Cui ◽  
Shuo Yang
Keyword(s):  
Wind Tunnel ◽  
Transmission Line ◽  
Wind Velocity ◽  
Transmission Lines ◽  
Damage Mechanism ◽  
Continuous Model ◽  
Vibrational Amplitude ◽  
Sudden Increase ◽  
Wind Field Model ◽  
Wind Velocities

Galloping of an iced transmission line subjected to a moderating airflow has been analysed in this study, and a new form of galloping is discovered both theoretically and experimentally. The partial differential equations of the iced transmission line are established based on the Hamilton theory. The Galerkin method is then applied on the continuous model, and a discrete model is derived along with its first two in-plane and torsional modes. A trapezoidal wind field model is built through the superposition of simple harmonic waves. The vibrational amplitude is generally observed to be more violent when the wind velocity decreases, except in the 2nd in-plane mode. Furthermore, the influence of the declining wind velocity rates on galloping is analysed using different postdecline wind velocities and the duration of the decline in wind velocities. Subsequently, an experiment has been carried out on a continuous model of an iced conductor in the wind tunnel dedicated for galloping. The first two in-plane modal profiles are observed, along with their response to the moderating airflow. Different declining rates of the wind velocity are also verified in the wind tunnel, which show good agreement with the results simulated by the mathematical model. The sudden increase in the galloping amplitude poses a significant threat to the transmission system, which also improves the damage mechanism associated with the galloping of a slender, a long structure with a noncircular cross-section.

A Wind Tunnel Simulation of Windproof Effectiveness of Simulated Shrubs with Different Spatial Configurations

2021 ◽  
Author(s):  
Xia Pan ◽  
Zhenyi Wang ◽  
Yong Gao ◽  
Xiaohong Dang
Keyword(s):  
Wind Tunnel ◽  
Wind Velocity ◽  
Optimized Design ◽  
Near Surface ◽  
Wind Tunnel Simulation ◽  
Spatial Configurations ◽  
Wind Velocities ◽  
Airflow Field ◽  
Row Space ◽  
Better Than

<p>A better understanding of the distribution of the airflow field and wind velocity around the simulated shrubs is essential to provide optimized design and maximize the efficiency of the windbreak forests. In this study, a profiling set of Pitot Tube was used to measure the airflow field and wind velocity of simulated shrubs by wind tunnel simulation. The effects of form configurations and row spaces of simulated shrubs on windproof effectiveness were in-depth studied. We come to the following results: The weakening strength to wind velocities of hemisphere-shaped and broom-shaped shrubs at 26.25 cm was mainly concentrated below 2 cm near the root and 6-14 cm in the middle-upper part, while the spindle-shaped shrubs were at 0.2-14 cm above the canopy, which meant the windproof effect of spindle-shaped shrubs was was better than that of hemisphere-shaped and broom-shaped. With the improvement of row spaces, the weakening height to wind velocities of the hemisphere-shaped shrubs at 35 cm was only concentrated below 2 cm near the root exclude for the 6-14 cm at 26.25 cm, which presented the hemisphere-shaped shrubs were not suitable for the layout of wide row space. Further, the form configurations of simulated shrubs had a stronger influence on wind velocity than row spaces. Moreover, the designed windbreaks with <em>Nitraria tangutorum</em>, which more effectively reduced the wind velocity among the windbreaks compared to behind the windbreaks. In the wind control system, the hemisphere-shaped windbreaks should be applied as near-surface barriers, and the windbreaks of broom-shaped and spindle-shaped can be used as shelterbelts above the near-surface. These analytical findings offer theoretical guidelines on how to arrange the windbreak forests for preventing wind erosion in the most convenient and efficient ways.</p>

scholarly journals Characteristics of Wind Velocity and Temperature Change Near an Escarpment-Shaped Road Embankment

2014 ◽  
Vol 2014 ◽  
pp. 1-13 ◽  
Author(s):  
Young-Moon Kim ◽  
Ki-Pyo You ◽  
Jang-Youl You
Keyword(s):  
Wind Tunnel ◽  
Temperature Change ◽  
Wind Velocity ◽  
Field Measurement ◽  
Wind Tunnel Test ◽  
Level Difference ◽  
Before And After ◽  
Wind Velocities ◽  
Large Level ◽  
Velocity Changes

Artificial structures such as embankments built during the construction of highways influence the surrounding airflow. Various types of damage can occur due to changes in the wind velocity and temperature around highway embankments. However, no study has accurately measured micrometeorological changes (wind velocity and temperature) due to embankments. This study conducted a wind tunnel test and field measurement to identify changes in wind velocity and temperature before and after the construction of embankments around roads. Changes in wind velocity around an embankment after its construction were found to be influenced by the surrounding wind velocity, wind angle, and the level difference and distance from the embankment. When the level difference from the embankment was large and the distance was up to 3H, the degree of wind velocity declines was found to be large. In changes in reference wind velocities around the embankment, wind velocity increases were not proportional to the rate at which wind velocities declined. The construction of the embankment influenced surrounding temperatures. The degree of temperature change was large in locations with large level differences from the embankment at daybreak and during evening hours when wind velocity changes were small.

scholarly journals SOME EFFECTS OF WIND ON THE GROWTH OF WHITE CLOVER (TRIFOLIUM REPENS L.) SEEDLINGS

1975 ◽  
pp. 253-253
Author(s):  
J.S. Bircham
Keyword(s):  
Wind Tunnel ◽  
Wind Velocity ◽  
White Clover ◽  
Trifolium Repens ◽  
Stages Of Growth ◽  
Wind Velocities ◽  
Total Plant ◽  
Trifolium Repens L

THE EFFECTS of wind velocity on Trifolium repens L. cv. 'Grasslands Huia' white clover seedlings were examined in a wind tunnel. Three experiments were conducted, each at a different wind velocity, in which wind was applied to seedlings at three distinct stages of growth (cotyledons, unifoliate leaf and trifoliate Icaf) for three periods of time (two, four and six days). The wind velocities were 5.0, 7.5 and 10.0 m/s. In all experiments total plant, shoot and root dry weights and shoot/root ratios were determined after 28 days.

scholarly journals Effect of wind on Svalbard reindeer fur insulation

Rangifer ◽  
2002 ◽  
Vol 22 (1) ◽  
pp. 93 ◽  
Author(s):  
Christine Cuyler ◽  
Nils A. Øritsland
Keyword(s):  
Heat Transfer ◽  
Wind Tunnel ◽  
Heat Loss ◽  
Wind Velocity ◽  
Rangifer Tarandus ◽  
Svalbard Reindeer ◽  
Significant Difference ◽  
Wind Velocities ◽  
Autumn And Winter

The heat transfer through Svalbard reindeer (Rangifer tarandus platyrhynchus) fur samples was studied with respect to wind velocity, season and animal age. A total of 33 dorsal fur sections were investigated using a wind tunnel. Insulation varied with season (calving, summer, autumn and winter). At zero wind velocity, fur insulation was significantly different between seasons for both calf and adult fur samples. At the same time, there was no significant difference between calf and adult insulation for the summer, autumn and winter seasons. Calf fur insulated as well as adult fur. Winter insulation of Svalbard reindeer was approximately 3 times that of summer. Increasing wind veloci¬ty increased heat loss, however, the increase was not dramatic. When wind coefficients (slope) of the heat transfer regression lines were compared, between season and between calf and adult, no significant differences were reported. All fur samples showed similar increases in heat transfer for wind velocities between 0 and 10 m.s-1. The conductance of winter fur of Svalbard reindeer was almost half that of caribou fur. Also, conductance was not as greatly influenced by wind as caribou fur

Cable rime accretion measurements on a Laurentian mountain

1990 ◽  
Vol 17 (6) ◽  
pp. 1022-1032 ◽  
Author(s):  
Pierre McComber ◽  
Jacques Druez ◽  
Béatrice Félin
Keyword(s):  
Transmission Line ◽  
Wind Velocity ◽  
Transmission Lines ◽  
Power Transmission ◽  
Winter Season ◽  
Similar Data ◽  
Power Transmission Lines ◽  
Mountain Ranges ◽  
Ice Shedding ◽  
Set Up

Rime is an important cause of damage to structures in northern Quebec, Canada, and a major concern about the reliability of power transmission lines. An atmospheric icing test line was set up at Mt. Valin (altitude 902 m), near Chicoutimi, to measure icing rates on stranded cables. Two cables, the first one 96.5 m (316.5 ft) in span and the second one 32.6 m (106.9 ft), were used to investigate transmission line icing by comparing icing, for a complete winter, on two stranded cables, 35 mm (1.38 in.) in diameter for the first cable and 8 mm (0.315 in.) for the second. Measurements taken during the 1986–1987 winter season are analyzed. Ice accretion and shedding are correlated with ice detector alarms and wind velocity respectively. The icing intensity, considered to be proportional to the number of icing alarms per unit time, is strongly correlated with the cable icing rate. A significant correlation is also verified between the wind velocity and the ice shedding. Results of this investigation indicate that wind velocity and icing detector alarm rate are important variables to predict total ice mass on cables exposed to winter in-cloud icing. With more similar data, the implementation of an empirical icing model to estimate cable icing in mountain ranges will become possible. Key words: transmission line icing, rime accretion, ice shedding.

Composite right/left-handed transmission line with array of thermocouples for generating terahertz radiation

2020 ◽  
Vol 92 (2) ◽  
pp. 20502
Author(s):  
Behrokh Beiranvand ◽  
Alexander S. Sobolev ◽  
Anton V. Kudryashov
Keyword(s):  
Transmission Line ◽  
Terahertz Radiation ◽  
Transmission Lines ◽  
Software Package ◽  
Optical Pulses ◽  
Capacitively Coupled ◽  
Voltage Difference ◽  
Left Handed ◽  
Microwave Transmission ◽  
Commercial Software Package

We present a new concept of the thermoelectric structure that generates microwave and terahertz signals when illuminated by femtosecond optical pulses. The structure consists of a series array of capacitively coupled thermocouples. The array acts as a hybrid type microwave transmission line with anomalous dispersion and phase velocity higher than the velocity of light. This allows for adding up the responces from all the thermocouples in phase. The array is easily integrable with microstrip transmission lines. Dispersion curves obtained from both the lumped network scheme and numerical simulations are presented. The connection of the thermocouples is a composite right/left-handed transmission line, which can receive terahertz radiation from the transmission line ports. The radiation of the photon to the surface of the thermocouple structure causes a voltage difference with the bandwidth of terahertz. We examined a lossy composite right/left-handed transmission line to extract the circuit elements. The calculated properties of the design are extracted by employing commercial software package CST STUDIO SUITE.

scholarly journals Time-Multiplexed Self-Powered Wireless Current Sensor for Power Transmission Lines

Energies ◽  
2021 ◽  
Vol 14 (6) ◽  
pp. 1561
Author(s):  
Hao Chen ◽  
Zhongnan Qian ◽  
Chengyin Liu ◽  
Jiande Wu ◽  
Wuhua Li ◽  
...  
Keyword(s):  
Energy Harvesting ◽  
Transmission Line ◽  
Transmission Lines ◽  
Power Transmission ◽  
Current Measurement ◽  
Current Sensor ◽  
Power Transmission Line ◽  
Power Transmission Lines ◽  
Current Sensing ◽  
Self Powered

Current measurement is a key part of the monitoring system for power transmission lines. Compared with the conventional current sensor, the distributed, self-powered and contactless current sensor has great advantages of safety and reliability. By integrating the current sensing function and the energy harvesting function of current transformer (CT), a time-multiplexed self-powered wireless sensor that can measure the power transmission line current is presented in this paper. Two operating modes of CT, including current sensing mode and energy harvesting mode, are analyzed in detail. Through the design of mode-switching circuit, harvesting circuit and measurement circuit are isolated using only one CT secondary coil, which eliminates the interference between energy harvesting and current measurement. Thus, the accurate measurement in the current sensing mode and the maximum energy collection in the energy harvesting mode are both realized, all of which simplify the online power transmission line monitoring. The designed time-multiplexed working mode allows the sensor to work at a lower transmission line current, at the expense of a lower working frequency. Finally, the proposed sensor is verified by experiments.

Study on the characteristics of secondary arc current of UHV high compensation degree TCSC line under the fine-tuning mode

2021 ◽  
Vol 0 (0) ◽  
Author(s):  
Baina He ◽  
Yadi Xie ◽  
Jingru Zhang ◽  
Nirmal-Kumar C. Nair ◽  
Xingmin He ◽  
...  
Keyword(s):  
Transmission Line ◽  
Transmission Lines ◽  
Stability Margin ◽  
Transmission Capacity ◽  
Fine Tuning ◽  
Series Compensation ◽  
Arc Current ◽  
Compensation Device ◽  
The Stability ◽  
Recovery Voltage

Abstract In the transmission line, the series compensation device is often used to improve the transmission capacity. However, when the fixed series capacitor (FSC) is used in high compensation series compensation device, the stability margin cannot meet the requirements. Therefore, thyristor controlled series compensator (TCSC) is often installed in transmission lines to improve the transmission capacity of the line and the stability of the system. For cost considerations, the hybrid compensation mode of FSC and TCSC is often adopted. However, when a single-phase grounding fault occurs in a transmission line with increased series compensation degree, the unreasonable distribution of FSC and TCSC will lead to the excessive amplitude of secondary arc current, which is not conducive to rapid arc extinguishing. To solve this problem, this paper is based on 1000 kV Changzhi-Nanyang-Jingmen UHV series compensation transmission system, using PSCAD simulation program to established UHV series compensation simulation model, The variation law of secondary arc current and recovery voltage during operation in fine tuning mode after adding TCSC to UHV transmission line is analyzed, and the effect of increasing series compensation degree on secondary arc current and recovery voltage characteristics is studied. And analyze the secondary arc current and recovery voltage when using different FSC and TCSC series compensation degree schemes, and get the most reasonable series compensation configuration scheme. The results show that TCSC compensation is more beneficial to arc extinguishing under the same series compensation. Compared with several series compensation schemes, it is found that with the increase of the proportion of TCSC, the amplitude of secondary arc current and recovery voltage vary greatly. Considering various factors, the scheme that is more conducive to accelerating arc extinguishing is chosen.

scholarly journals Galloping Stability and Wind Tunnel Test of Iced Quad Bundled Conductors considering Wake Effect

2020 ◽  
Vol 2020 ◽  
pp. 1-15
Author(s):  
Xiaohui Liu ◽  
Ming Zou ◽  
Chuan Wu ◽  
Mengqi Cai ◽  
Guangyun Min ◽  
...  
Keyword(s):  
Wind Tunnel ◽  
Transmission Lines ◽  
Degrees Of Freedom ◽  
Wind Tunnel Test ◽  
Aerodynamic Coefficients ◽  
Wake Effect ◽  
Aerodynamic Coefficient ◽  
Set Up ◽  
The Stability ◽  
Three Degrees Of Freedom

A new quad bundle conductor galloping model considering wake effect is proposed to solve the problem of different aerodynamic coefficients of each subconductor of iced quad bundle conductor. Based on the quasistatic theory, a new 3-DOF (three degrees of freedom) galloping model of iced quad bundle conductors is established, which can accurately reflect the energy transfer and galloping of quad bundle conductor in three directions. After a series of formula derivations, the conductor stability judgment formula is obtained. In the wind tunnel test, according to the actual engineering situation, different variables are set up to accurately simulate the galloping of iced quad bundle conductor under the wind, and the aerodynamic coefficient is obtained. Finally, according to the stability judgment formula of this paper, calculate the critical wind speed of conductor galloping through programming. The dates of wind tunnel test and calculation in this paper can be used in the antigalloping design of transmission lines.

Development on Environmental Geotechnology for Overhead Transmission Line Foundation Engineering in China

2012 ◽  
Vol 610-613 ◽  
pp. 2813-2818
Author(s):  
Xian Long Lu ◽  
Zeng Zhen Qian
Keyword(s):  
Transmission Line ◽  
Environmental Protection ◽  
Transmission Lines ◽  
Water Conservation ◽  
Design Method ◽  
Foundation Engineering ◽  
Foundation Construction ◽  
Overhead Transmission Line ◽  
Tower Foundation ◽  
Soil And Water

This paper presents the concept and the fundamental issues and the development on the environmental geotechnology in transmission lines foundation engineering. Namely, environmental geotechnology and theory is to study the restriction effects of environment on the transmission line routes, foundation selection and reliability, to predict the results of transmission line foundation construction on the environment, and to study on countermeasures of environmental protection in transmission foundation engineering. And then, from the above three aspects, the design method combined strength and displacement for tower foundation, the selection on foundation types and technical scheme for transmission line tower, and the countermeasures for soil and water conservation, the author introduces the development and practice of environmental geotechnology for transmission lines foundation engineering in China.

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