• Wind and Structures
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• 제28권3호
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• pp.155-170
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• 2019

This paper presents a novel test method for the galloping of iced conductor using wind generated by a moving vehicle which can produce relative wind field. The theoretical formula of transiting test is developed based on theoretical derivation and field test. The test devices of transiting test method for aerodynamic coefficient and galloping of an iced conductor are designed and assembled, respectively. The test method is then used to measure the aerodynamic coefficient and galloping of iced conductor which has been performed in the relevant literatures. Experimental results reveal that the theoretical formula of transiting test method for aerodynamic coefficient of iced conductor is accurate. Moreover, the driving wind speed measured by Pitot tube pressure sensors, as well as the lift and drag forces measured by dynamometer in the transiting test are stable and accurate. Vehicle vibration slightly influences the aerodynamic coefficients of the transiting test during driving in ideal conditions. Results of transiting test show that the tendencies of the aerodynamic coefficient curve are generally consistent with those of the wind tunnel tests in related studies. Meanwhile, the galloping is fairly consistent with that obtained through the wind tunnel test in the related literature. These studies validate the feasibility and effectiveness of the transiting test method. The present study on the transiting test method provides a novel testing method for research on the wind-resistance of iced conductor.

• Structural Engineering and Mechanics
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• 제75권4호
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• pp.465-475
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• 2020

The analytical approach for stability and response of iced conductor under uniform wind or turbulent wind is presented in this study. A nonlinear dynamic model is established to describe the motion of iced conductor galloping. In the case of uniform wind, the stability condition is derived by analyzing the eigenvalue associated with linearized matrix; The first order and second order approximation of galloping amplitude are obtained using multi-scale method. However, real wind has random characteristics essentially. To accurately evaluate the performance of the galloping iced conductor, turbulence wind should be described by random processes. In the case of turbulence wind, the Lyapunov exponent is conducted to judge the stability condition; The probability density of displacement is obtained by using the path integral method to predict galloping amplitude. An example is proposed to verify the effectiveness of the previous methods. It is shown that the fluctuating component of wind has little influence on the stability of iced conductor, but it can increase galloping amplitude. The analytical results on stability and response are also verified by numerical time stepping method.

• 제어로봇시스템학회:학술대회논문집
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• 제어로봇시스템학회 2003년도 ICCAS
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• pp.128-133
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• 2003

In this paper, we have proposed a method by using virtual simulation to calculate the behaviors of spacers to avoid conductor galloping with the hanging composite polymer spacer between conductors on different phases. We have considered with three types of modeling considerations for the analysis of galloping in power transmission lines, such as iced-single conductors without spacer, iced-single conductors with spacers, and iced-two bundle conductors with spacers. In simulation, the finite element method is used to calculate the structural response with geometric nonlinear behavior. The iced conductor is modeled by two beam-element faces with which it is connected. The ANSYS program is applied too. First, the calculation results show that the two beam-element model is very suitable to make a virtual simulation. Second, the amplitude of conductor galloping is reduced after hanged spacers. Third, when number of spacer is increased, the maximum magnitude of natural frequency of iced conductor will reduce. Final, the behaviors of spacers are verified in viewpoint of standard cases.

• Wind and Structures
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• 제29권4호
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• pp.225-234
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• 2019

Conductor galloping is a common disaster for the transmission lines. Among the existing analytical methods, the wind tunnel test is highlighted as the most effective approach to obtain the aerodynamic coefficients. In this paper, the aerodynamic coefficients of 12 conductor models covered with the crescent-shaped ice, which were fabricated considering the surface roughness of the iced conductor, were obtained based on the wind tunnel test. The influence of the Reynolds number and the shape parameter ${\beta}$, defined as the ratio of ice thickness to the diameter, were investigated. In addition, the effect of surface roughness of the iced conductor was discussed. Subsequently, unsteady areas of conductor galloping were calculated according to the Den Hartog criterion and the Nigol criterion. The results indicate that the aerodynamic coefficients of iced conductors change sharply at the attack angles of $20^{\circ}$ and $170^{\circ}$ with the increase of ${\beta}$. The surface roughness of iced conductors changed the range of attack angle, which was influenced by the increase of the Reynolds number. The experimental results can provide insights for preventing and controlling galloping.

• Wind and Structures
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• 제18권2호
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• pp.135-154
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• 2014

Aerodynamic characteristics of crescent and D-shape bundled conductors were measured by high frequency force balance technique in the wind tunnel. The drag and lift coefficients of each sub-conductor and the whole bundled conductors were presented under various attack angles of wind. The galloping possibility of bundled conductors is discussed based on the Den Hartog criterion. The influence of icing thickness, initial ice accretion angle and sub-conductor on the aerodynamic properties were investigated. Based on the measured aerodynamic force coefficients, a computationally efficient finite element method is also implemented to analyze galloping of iced bundled conductors. The analysis results show that each sub-conductor of the bundled conductor has its own galloping feature due to the use of aerodynamic forces measured separately for every single sub-conductors.

• Structural Engineering and Mechanics
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• 제75권4호
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• pp.487-496
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• 2020

Most of the previous works on numerical analysis of galloping of transmission lines are generally based on the quasisteady theory. However, some wind tunnel tests of the rectangular section or hangers of suspension bridges have shown that the galloping phenomenon has a strong unsteady characteristic and the test results are quite different from the quasi-steady calculation results. Therefore, it is necessary to check the applicability of the quasi-static theory in galloping analysis of the ice-covered transmission line. Although some limited unsteady simulation researches have been conducted on the variation of parameters such as aerodynamic damping, aerodynamic coefficients with wind speed or wind attack angle, there is a need to investigate the numerical simulation of unsteady galloping of two-dimensional iced transmission line with comparison to wind tunnel test results. In this paper, it is proposed to conduct a two dimensional (2-D) unsteady numerical analysis of ice-covered transmission line galloping. First, wind tunnel tests of a typical crescent-shapes iced conductor are conducted firstly to check the subsequent quasisteady and unsteady numerical analysis results. Then, a numerical simulation model consistent with the aeroelastic model in the wind tunnel test is established. The weak coupling methodology is used to consider the fluid-structure interaction in investigating a two-dimension numerical simulation of unsteady galloping of the iced conductor. First, the flow field is simulated to obtain the pressure and velocity distribution of the flow field. The fluid action on the iced conduct at the coupling interface is treated as an external load to the conductor. Then, the movement of the conduct is analyzed separately. The software ANSYS FLUENT is employed and redeveloped to numerically analyze the model responses based on fluid-structure interaction theory. The numerical simulation results of unsteady galloping of the iced conduct are compared with the measured responses of wind tunnel tests and the numerical results by the conventional quasi-steady theory, respectively.

• Wind and Structures
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• 제34권2호
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• pp.173-183
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• 2022

The galloping of iced conductors has long been a severe threat to the safety of overhead transmission lines. Compared with normal transmission lines, the ultra-high-voltage (UHV) transmission lines are more prone to galloping, and the damage caused is more severe. To control the galloping of UHV lines, it is necessary to conduct a comprehensive analysis of galloping characteristics. In this paper, a large-span 1000-kV UHV transmission line in China is taken as a practical example where an 8-bundled conductor with D-shaped icing is adopted. Galerkin method is employed for the time history calculation. For the wind attack angle range of 0°~180°, the galloping amplitudes in vertical, horizontal, and torsional directions are calculated. Furthermore, the vibration frequencies and galloping shapes are analyzed for the most severe conditions. The results show that the wind at 0°~10° attack angles can induce large torsional displacement, and this range of attack angles is also most likely to occur in reality. The galloping with largest amplitudes in all three directions occurs at the attack angle of 170° where the incoming flow is at the non-iced side, due to the strong aerodynamic instability. In addition, with wind speed increasing, galloping modes with higher frequencies appear and make the galloping shape more complex, indicating strong nonlinear behavior. Based on the galloping amplitudes of three directions, the full range of wind attack angles are divided into five galloping regions of different severity levels. The results obtained can promote the understanding of galloping and provide a reference for the anti-galloping design of UHV transmission lines.