Iced Conductor Research Articles

An aerodynamic anti-galloping technique of iced 8-bundled conductors in ultra-high-voltage transmission lines

Galloping of iced conductors is a kind of self-excited aeroelastic vibration with low frequency and large amplitude causing various damages on transmission tower-line systems. A newly designed galloping simulation device is employed in the wind tunnel for developing an aerodynamic anti-galloping technique of iced 8-bundled conductors in ultra-high-voltage (UHV) transmission lines. The anti-galloping technique is based on the proposed rotary clamp spacers, which allow the connected sub-conductors to rotate around its axis. Iced 8-bundled conductor models of UHV lines with and without twistable sub-conductors have been tested in the wind tunnel under various wind attack angles and five different ratios of vertical vibration frequency over the torsional. Aerodynamic damping ratios were identified from measured response data, and were used as indicators of galloping for iced 8-bundled conductor models with and without twistable sub-conductors. Equations of motion for iced 8-bundled conductors with and without twistable sub-conductors are respectively established, and the aerodynamic instability of the system can then be predicted by solving the eigenvalue problem associated with equations of motion. In order to further validate the anti-galloping effects of the rotary clamp spacers, finite element simulation has been conducted for a real UHV transmission line with a span of 500 m located in the galloping-prone area.

Numerical Simulation of Fluid-Structure Interaction of D-shape Iced Conductor

At present, the numerical simulation on the aerodynamic response and force of the iced conductor are mainly based on the quasi steady criterion, which ignored the interaction between the conductor and the flow field. This paper presents a numerical study of three kinds of fluid-structure interaction models for D-shape conductor. The effects of reduced velocity, degree of freedom and wind attack angle on aerodynamic response of the iced conductor are discussed. The results show that the rotational freedom has certain influence on the across-wind vibration. The mean value of drag coefficient decreases with the increase of wind attack angle, while the lift and moment coefficient increase with the increase of wind attack angle. When the maximum amplitude of vibration displacement occurs, the corresponding reduced velocity is not entirely consistent with that of the maximum aerodynamic force.

Modeling and Analysis of Progressive Ice Shedding along a Transmission Line during Thermal De-Icing

Progressive ice shedding (PIS) along transmission lines is a common type of ice shedding during thermal de-icing that requires investigation to ensure the security of transmission lines. In current research, PIS is commonly analyzed using a constant speed for ice detaching from the conductor, which is not accurate for PIS simulation. Therefore, a mechanical model of PIS is established in this study to analyze PIS during thermal de-icing. First, an ice detachment model during thermal de-icing is built to determine the detachment times of the initial ice and remaining ice. Then, a two-node isoparametric truss element is employed to derive the static and dynamic equilibrium equations of an iced conductor to simulate the dynamic response of PIS. Relative to commercial software, these equations can easily accommodate the changing mass of ice with the flow of melted water. The dynamic equilibrium equations are then solved using the ice detachment model to obtain the dynamic response of PIS. Finally, small-scale and full-scale experimental results are employed to verify the proposed method. The simulation results show that the results of the proposed method are more consistent with the experimental results than are the results of existing methods that assume a constant propagation speed. The proposed method can be further applied to optimize transmission line designs and evaluate the application of thermal de-icing devices.

Transiting test method for galloping of iced conductor using wind generated by a moving vehicle

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.

Wind Tunnel Test Investigation on Unsteady Aerodynamic Coefficients of Iced 4‐Bundle Conductors

Iced conductor motion is induced by the aerodynamic instability of these conductors. The unsteady aerodynamic characteristics are different from the steady aerodynamic characteristics. The unsteady aerodynamic coefficients of typical iced conductors’ models under torsional motion are measured by the unsteady wind tunnel test. The unsteady aerodynamic coefficients of crescent‐shape and sector‐shape iced 4‐bundle conductors under different torsional motion frequencies, wind velocities, and ice thicknesses are obtained. Wind test results show that there are significant differences between the unsteady and steady aerodynamic coefficients. The unsteady aerodynamic coefficients curve is a loop which is different from the steady aerodynamic coefficients. In addition, the obvious differences exist between unsteady aerodynamic coefficients of crescent‐shape and sector‐shape iced bundle conductors. Critical parameters, including torsional motion frequencies, wind velocity, ice shape, and ice thickness, have significant influences on unsteady aerodynamic coefficients. It shows that the wind tunnel experiment results are able to provide necessary data for the investigation of iced bundle conductor motion and their prevention techniques.

Galloping Control for Iced Conductors Using Tuned Mass Dampers with Fixed Time‐Delayed Feedback

A tuned mass damper with fixed time‐delay feedbacks (TTMD) is first applied to suppress galloping of iced conductors. It is different from general time‐delay feedback control, which also connects an added mass to a galloping body and can absorb vibrational energy. The two‐degrees‐of‐freedom model captures the essential mechanical behaviors of iced conductors with TTMD undergoing galloping. The harmonic balance method is then employed to obtain the approximate analytical solutions of the system. Particularly, the expressions of galloping amplitude and angle frequency were obtained. Then the influence regulations of the time‐delay parameter T and strength parameter K on galloping control are fully analysed. The results show the added fixed time‐delay feedback control can promote the TTMD’s effect, when suitable time‐delay parameter T and strength parameter K are chosen. Moreover, the response amplitude and natural frequency change periodically with time‐delay parameter T. With strength parameter K increasing, the response amplitude increases or decreases for a fixed value of T and the TTMD’s effect can be enhanced.

Study on wind tunnel test and galloping of iced quad bundle conductor

Conductor galloping is a common phenomenon during the operation of the transmission line, which can easily result in electrical and mechanical accidents such as tower collapses and interphase flashover. And aerodynamic parameters are key factors to study galloping. In this paper, the aerodynamic parameters of crescent-shaped and D-shaped conductors, which are two typical iced conductors, are studied by wind tunnel test. The instability analysis is carried out according to Den Hartog instability mechanism and the linear galloping model. The results indicate that wind velocity, ice thickness, conductor type, bundle spacing and splitting number all have a great influence on aerodynamic parameters and conductor galloping. Then the galloping situation of a 500 kV quad bundle conductor are simulated according to the parameters obtained from wind tunnel test. The calculating results correspond with the actual situation. The results obtained in this paper are important to predict the galloping amplitudes under different weather conditions and investigate anti-galloping technology of iced quad bundle conductor.

Mitigation of conductor line galloping by a direct cable-connection to non-conductive composite power pylons

Steel lattice towers with suspended insulator strings are typically used to carry high-voltage overhead transmission lines. The installation of non-conductive power pylons made of glass fibre reinforced plastics enables a direct cable-pylon connection, as the composite structure acts as an unibody insulator. At the same time, wind-induced vibrations, such as the severe cable vibration phenomenon galloping, will consequently be directly transferred to the slender composite mast structure, potentially leading to extensive damage. The aim of the study is therefore to investigate the galloping behaviour of iced conductor lines with regard to different cable support conditions. Furthermore, additional damping in the composite power pylon structure is assumed to mitigate conductor line galloping and therefore reduce the risk of phase flash-overs between adjacent conductor lines. A numerical galloping simulation is carried out in order to evaluate the effect of a rigid cable-pylon connection with enhanced damping properties on the cable vibration amplitudes. A pylon-cable system, consisting of 3×300 m spans, is investigated. It was found that the support conditions of the conductor lines have a significant influence on the galloping mode, the vibration amplitudes and the orientation of the characteristic galloping ellipse. The addition of damping to the pylon decreases the vibration amplitudes slightly and leads to a re-orientation of the galloping ellipse.

Wind Tunnel Tests on Aerodynamic Characteristics of two types of Iced Conductors with Elastic Support

The wind tunnel tests were carried out to obtain the variation laws of static aerodynamic characteristics of crescent and D-shape iced conductor with different wind velocities, wind attack angles and torsional elastic support stiffness. Test results show that the variation of wind velocity has a relatively large influence on the aerodynamic coefficients of crescent conductor with torsional elastic support 1. However, the influence on that of D-shape conductor is not obvious. With the increase of the torsional elastic support stiffness, the lift and moment coefficient curves of the crescent iced conductor form an obvious peak phenomenon in the range of 0 ° ∼30°. Meanwhile, the wind attack angle position corresponding to the maximum value of the lift and moment coefficients of the D-shape iced conductor appear a backward moving phenomenon.

An Online Technology for Measuring Icing Shape on Conductor Based on Vision and Force Sensors

The icing on transmission line conductor usually causes accidents such as conductor galloping, conductor breaking, line tripping, and even network paralyzing, which could bring serious threats to the safe operation of the power system. The conductor icing shape not only has a great influence on the estimate to melting ice time or melting ice current, but also directly affects the mechanical calculation of conductor galloping. Therefore, it is paramount to determine the conductor icing shape. Many available artificial measurements are inaccurate and even ineffective enough in some cases. This paper proposes a novel online technology for measuring icing shape on transmission line conductor based on vision and force sensors. The proposed technique consists of three parts, namely, the online device based on vision and force sensors, the communication network, and the monitoring center. The images of the iced conductor are captured from two cameras, and the processing algorithms are used to extract the average diameters of the iced conductor. The equivalent cross-sectional area is also obtained by the force sensors and a built-in mechanics model. The icing shape description algorithm is proposed to accurately represent the icing shape. We thoroughly analyze the performance of the technology by a series of experiments under artificial icing simulations and natural conditions. The experimental results demonstrate that the proposed method can measure the icing shapes with the overlap ratio of greater than 0.85. In addition, the proposed measuring technology shows satisfactory results on the field tests carried out on operating transmission lines.

Effect of temperature on galloping of iced conductors

This article investigates the effect of temperature on galloping of iced conductors, accounting for the influence of sagging and geometric nonlinearity. By extending Irvine’s cable theory to thermo-elasticity problems, an analytical model is proposed to evaluate the effect of thermal stress on galloping of transmission lines. The Lindstedt–Poincare method is then used to solve the model so that the closed-form approximate solution is derived. The derived solution is then verified using numerical examples, which also displays the variation in galloping amplitude with temperature, as well as with respect to static horizontal tension, span length and wind speed. It is concluded that the thermal stress may have effects on galloping amplitude and that the temperature effects should not be neglected. Furthermore, the effect of temperature on galloping amplitude is related to static horizontal tension, span length and wind speed, and a positive temperature change does not necessarily decrease the galloping amplitude.

Isogeometric Collocation Method for the Galloping of an Iced Conductor

AbstractA computationally efficient isogeometric collocation (IGA-C) method based on nonuniform rational B-splines (NURBS) is adopted to analyze the large amplitude, low frequency, and self-excited...

Study on galloping behavior of iced eight bundle conductor transmission lines

Wind tunnel test was carried out to obtain the aerodynamic coefficients of an eight bundle conductor accreted with crescent-shaped ice. A user-defined cable element with torsional degree of freedom is developed in ABAQUS software to capture the torsional deformation of the iced conductors during galloping. By means of the user-defined cable element, different damping ratios in in-plane, out-of-plane and torsional directions of the conductors can be defined and the aerodynamic forces varying with their motion status can be exerted on the conductors conveniently when ABAQUS is used to simulate galloping of transmission lines. A wind tunnel test to model galloping of an iced eight bundle conductor segment was carried out, and the validity of the numerical simulation method is demonstrated by the agreement of the galloping orbit of the bundle conductor segment model recorded in the test and that by the numerical simulation. Furthermore, galloping behavior, including dynamic responses, galloping orbits, frequencies, vibration modes and amplitudes, of typical iced eight bundle conductor transmission lines in the cases of different span lengths, initial tensions in sub-conductors, wind velocities, angles of wind attack and damping ratios is studied, and the galloping behavior of the lines with internal resonance conditions is discussed. The obtained results may provide a fundamental tool for the development of anti-galloping techniques of eight bundle conductor transmission lines.

Effect of the Reynolds number on the aerodynamic forces and galloping instability of a cylinder with semi-elliptical cross sections

The effects of the Reynolds number on the aerodynamic forces and galloping instability of a semi-elliptical cross-section, which are used to simulate the shape of the iced conductors, have not been fully studied. Simultaneous multi-pressure wind tunnel experiments were conducted to explore the aerodynamic forces on cylinder with semi-elliptical cross-sections; the Reynolds number was in the sub-critical and critical regimes. A unified single-degree-of-freedom (SDOF) approach and a three-degree-of-freedom (3-DOF) model were used to analyze the galloping instability with the Reynolds number in the following regime: Re=34k–175k. The variation in the aerodynamic force with the angle of attack is sensitive at the critical Reynolds number; at this critical regime, the sudden decrease in the lift coefficient value with an increasing angle of attack is sufficient to create negative aerodynamic damping. The galloping instability analysis shows that the occurrence of negative aerodynamic damping strongly depends on the critical flow state. In all cases considered in the present work, the critical Reynolds number effects are shown to include aerodynamic forces that could well be responsible for the whole range of translational galloping instabilities and part range of torsional flutter and 3-DOF galloping instabilities for semi-elliptical cylinders.

The Numerical Simulation of Iced Conductor and Research of Influencing Factors

In order to study the influence of some key factors such as the turbulence intensity related to micro topography and the diameter of conductor to the aerodynamic characteristics of iced conductor , the model is built based on the characteristic of iced conductor with crescent type ,to simulate the aerodynamic parameters for it and compare with the wind tunnel tests .The results show that we can make supplement reference to the wind tunnel tests through the numerical simulation method. Besides , we adjust the model and make research for the influence of diameter of conductor. The aerodynamic parameters we get can provide some reference to the research of galloping conductor.

English

English

The Aerodynamic Analysis for Iced Four Bundled Transmission Lines with Typical Crescent

Despite the fact that the wind tunnel tests have been carried out on iced transmission lines subjected to wind load, it is not practical to do wind tunnel tests due to its high cost. This paper describes a detailed numerical simulation method that can be used to instead of wind tunnel tests. Based on the galloping mechanism of iced transmission lines, the aerodynamic test was simulated with the typical crescent super-large thickness iced four bundled conductors. One of the results highlighted in this study is that the wind angle of attack had significant influence on the aerodynamics of iced conductors. The Den-Hartog and O.Nigol coefficient were calculated to determine galloping of iced transmission lines, comparing with the reference of wind tunnel test in the Zhejiang university, the range of the wind angle of attack to the bundled conductor which can lead to gallop is larger than single wire, but the absolute value of amplitude is less than the single conductor, split conductor is more likely to gallop than single conductor.

Numerical Simulation of Galloping for Iced Quad-Bundled Conductor

The theoretical study of galloping can effectively promote anti-galloping techniques. Cable element is utilized to imitate the bundled conductor, and beam elements are used to simulated the spacers, established galloping finite element analysis model which can consider sub-conductors wake interference. The finite element equation was solved by time integration method and the calculation program was compiled by MATLAB. Through numerical simulation analysis, compared the dancing in the case of considering the effect of the sub-conductor wake and ignoring the effect of the sub-conductor wake. The results showed that considering the effect of the wake on aerodynamic loads has a greater vertical vibration amplitude. This method can provide reference for the study of prevention technology on dancing.

Analysis on Galloping Responses of Transmission Tower-Line System

Nonlinear finite element model of a transmission tower-line system was set up and galloping of iced bundle conductors in the system was numerically simulated by means of ANSYS software. Based on galloping trajectories, vibration frequency, galloping order, conductor tension; unbalanced tension characteristics of iced conductors, it was shown that values of the conductor amplitudes by the tower-line system model are increased by 20% compared to the conductor model. The values of the strain tower unbalanced tensions by the tower-line system model are decreased by 20% and the values of the suspension tower unbalanced tensions by the tower-line system model are decreased by 62.5% compared to the conductor model conductor-insulator mode1. The galloping order is different for different span, due to the impact of the order of galloping. The amplitude of the vertical galloping is increasing while the increasing span, but it is not linear increase.

Study on the influence of charged glaze on the corona onset voltage of bundle conductor

Glaze grows on the conductor surface will affect corona onset voltage (COV). Wires iced under voltage is often neglected and scaled models always adopted to study the actual bundle conductors, there is no lights have been thrown into the down-trend of COV during charged icing. AC corona tests of iced bundle conductors implemented in the Multifunction Climate Chamber, the UV imaging camera and I-U curve fitting applied to analyze the COV. Finite element models of iced conductor established to discuss how the glaze icicles affect electric field. Results show that glaze cut the COV down greatly. Different icicle morphology leads to distinct COV values. With more sub-conductors, bundle conductor gets higher COV in the same icing time. With the Increase of icing time, COV decreases with the rate slow down. Higher conductivity has no effect on morphology but reduces the COV. Sharper icicles lead to more seriously field distorted and lower COV values. This paper provides reference for selection and designation of transmission line in glaze icing areas.