Galloping Of Iced Conductors Research Articles

Study on the Effect of Anti-galloping Device with Cubic Stiffness and Particle Damping

The galloping of iced conductors is a common disaster of overhead conductors. Most traditional anti-galloping devices lack a nonlinear dynamic vibration absorber; hence, they have a limited anti-galloping effect. In this study, we designed, optimized, and tested an electric power fitting and an anti-galloping device with cubic stiffness and particle damping for ultra-high-voltage (UHV) transmission lines. We built a nonlinear dynamic model of the coupling galloping system comprising split conductors and anti-galloping devices. The harmonic balance method obtained the steady-state analytical solutions and corresponding averaged equations. The test spans in the laboratory were used to design the test program and equipment. We verified the accuracy of the nonlinear dynamic model and the harvesting effect of the anti-galloping device with cubic stiffness and particle damping. The theoretical and experimental results were highly consistent, and in the range of (0, 2] Hz, the anti-galloping device reduced the galloping amplitude. Therefore, cubic stiffness and particle damping can effectively improve the anti-galloping ability of UHV transmission lines, prolonging their service period.

Study on looseness characteristics of bolted joints of transmission towers under lateral vibration

transmission towers have been subjected to alternating loads caused by the galloping of iced conductors for a long time, and their fastening bolts are easy to loosen or break, which seriously threatens the safe operation of transmission lines. Through the transverse vibration test of M20 bolts commonly used in transmission towers, the vibration frequency and amplitude are changed, and the change law of the preload of bolt joints is studied. The results show that with the increase of the initial preload, the decline speed of bolt clamping force decreases significantly; The clamping force drop curve of M20 bolt is fitted by shivakumar crews model, which is very consistent with the actual test curve.

Data-driven sparse identification of galloping model of iced quad bundle conductors

The galloping of iced conductors is a serious threat to the safe operation of power systems. Establishing an accurate galloping model of iced conductors has always been a difficult point in galloping research. Therefore, the sparse identification of nonlinear dynamics (SINDy) algorithm is used to identify the galloping model from noise measurement data. A theoretical model of galloping of iced quad bundle conductors is established. Meanwhile, the algorithm is used to identify the simulated data of the theoretical model. The parameter identification ability of the algorithm under noisy velocity measurement is analyzed. An excellent denoising method was selected for data preprocessing, and then the model identification effect of the algorithm after data preprocessing is studied. Besides, the accuracy of the prediction model based on this algorithm and the support vector regression (SVR) prediction model under different training data lengths are compared. The results show that the model identified by the SINDy algorithm in the noise measurement data after data preprocessing has high accuracy and robustness. Moreover, the amount of data used is small. The model identified by this algorithm plays an important role in the rapid investigation, prediction and early warning of galloping phenomena.

A New Method of Conductor Galloping Monitoring Using the Target Detection of Infrared Source

Because the galloping of iced conductors is one of the main disasters in the State Grid, resulting in huge economic and property losses every year, the research on relevant monitoring methods is of great significance. The existing galloping monitoring technology is mainly based on the contact detection method, which presents potential electrical hazards and power supply problems. In this paper, a conductor galloping monitoring method based on the target detection of infrared sources is put forward to overcome the shortcomings of existing methods. In other words, an infrared source label is installed on the conductor spacer, high-definition night vision infrared cameras are installed on electric power towers to take video of the infrared source labels, and the characteristic amplitude of conductor galloping is calculated by an image recognition and tracking algorithm. The practical application results indicate that the method has the advantages of non-contact detection, safety and reliability, and high detection accuracy.

Energy Method to Compute the Maximum Amplitudes of Oscillation Due to Galloping of Iced Bundled Conductors

The paper presents a modal model to describe the interaction between a 4-conductor bundle and wind. A finite-element model of the bundle is used to perform a linear analysis, to extract mode shapes and natural frequencies of the system. The motion of the expanded bundle is then described through mode coordinates representing the first horizontal, vertical and torsional modes. Wind tunnel tests were performed adding templates over the cables to mimic the presence of ice over the same conductor bundle; tests allowed to characterize the aerodynamic coefficients of the entire bundle and provided data for the model validation. The model was then applied to a case study to predict the maximum oscillations produced by iced conductor galloping. Time-domain simulations were used for the purpose, together with an alternative approach named energy method; this last directly estimates the amplitude of limit cycles avoiding the integration of the equations of motion and can be much more useful from the engineering point of view.

Energy harvesting from iced-conductor inspired wake galloping

Energy harvesting from wake galloping of crescent-shape and D-shape cross-section bluff bodies inspired by galloping of iced conductors is investigated. Analytical models are derived in the framework of electromechanical extension of the Hamilton’s principle, Euler–Bernoulli beam assumption and quasi-steady hypothesis. Experiments are performed in an open-circuit boundary layer wind tunnel to investigate the wake effects of the upstream fixed interference cylinder on the performance of the downstream energy harvester and validate the analytical model. The observations are explained with the wake characteristics and lift force as determined from Large Eddy Simulation. The results show that the wake effects of the upstream fixed interference cylinders can positively enhance the performance of the downstream energy harvester. The wake galloping energy harvesters with the iced D-shape and crescent-shape bluff bodies display remarkable enhancement in terms of the harvested power density for wide interference spacing range when compared to energy harvesters placed in the wake of a non-iced circular bluff body. The power density of the wake galloping energy harvester with the iced-conductor inspired bluff bodies at the optimal interference spacing is about 63 times that of the power density of the wake galloping energy harvester with the classic circular bluff body.

The nonlinear galloping of iced transmission conductor under uniform and turbulence wind

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.

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.

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.

Numerical Simulation of Iced Conductor Galloping

Numerical Simulation of Iced Conductor Galloping

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.

Two-Parameter Bifurcation and Stability Analysis for Nonlinear Galloping of Iced Transmission Lines

AbstractThis paper presents an analytical approach in the study of bifurcation and stability behavior for nonlinear galloping of iced transmission lines. Equations of motion are established to describe three-dimensional galloping behavior observed on iced transmission lines. Stability analysis of iced conductor galloping is carried out. The center manifold theory, together with the normal form theory, is used to derive the governing bifurcation equations. A new formula is also proposed to calculate the maximum dynamic tension of iced conductors. The technique developed in this paper is implemented using a symbolic analysis module for practical usage. A real transmission line with a span of 244 m, which was damaged by the galloping accidents, is presented to demonstrate the effectiveness and accuracy of the developed two-parameter bifurcation analysis technique for nonlinear galloping of iced conductors. The galloping amplitudes in three orthogonal directions are analytically obtained for a broad range of ...

Experimental Investigation and Theoretical Analysis on Galloping of Iced Conductors

The aerodynamic forces of two typical iced conductor models are obtained by high frequency balance technique in wind tunnel test. The effects of wind directions and turbulence intensity on aerodynamic forces coefficients are discussed. An analytical expression for predicting the galloping instability trends in arbitrary directions is derived. An aerodynamic model considering the dynamic swing is developed according to the quasi-steady theory. Galerkins procedure is employed to discrete the governing equations of transmission line, which is modeled as a suspended homogeneous elastic cable having a small equilibrium curvature and neglecting the shear deformation. The forth order Runge-Kutta method are applied to obtained the approximate numerical results of iced transmission line galloping.

Galloping of a single iced conductor based on curved-beam theory

Based on the displacement interpolations and curvature–displacement relationship of spatial curved beam theory, a finite element model of iced conductor galloping is presented, which involves 3 translational degrees of freedom (DOF) and 3 rotational DOF. The nonlinearity and coupling of translational and torsional movement can be taken into account in this model. A nonlinear iteration algorithm is employed to solve for the equilibrium position under eccentric gravity loads and the quasi-steady aerodynamic forces. The linearized movement equations are derived and the stability of the equations is judged according to the initial equilibrium solution (IES). Time integration is also performed in the sub-space. An example of three thicknesses of iced C-shaped conductors shows that the update of aerodynamic forces will greatly affect the initial equilibrium position, which will result in different critical wind speeds and galloping amplitudes of an iced transmission line. Different types of galloping, such as one-loop or two-loop, will occur at different wind attack angles.

Experimental Simulation on Aerodynamic Character of D-Shaped Iced Conductor

The dynamics force of iced-conductor is the driving force of galloping; its variation is depended on the aerodynamic character of iced conductor. The aerodynamic character of iced conductor is the key factor of galloping of iced-conductor, but the result of theoretically analysis and numerical simulation isn’t suited for the requirement of transmission line project. In the paper, basing on the theoretically analysis and numerical simulation, the simulation tests in wind tunnel of D-shaped iced conductor is stetted up and put into practice under different wind speed and iced thickness, and then the systemic study is carried into execution. The result of research is indicated that there is a better coherence between the numerical simulation and experiment test, and the variation rules of parameters is obvious with the different iced thickness, the result of numerical simulation is the beneficial supplement to the experiment test. The result can not only provide the original date for the galloping analysis, but also validate the affectivity of numerical simulation, support the research of mechanism and control of galloping.

Studies on Galloping of Iced Conductor Based on Tower-Line Coupling System – Aerodynamic Loads

Based on the second development at the ANSYS computing platform, finite element model of a Tower-Line Coupling system was established. The computational fluid dynamics module (CFX) was used for the numerical simulation of the aerodynamic characteristics of iced conductor. On the basis of the Kaimal spectrum, fast Fourier transform was introduced to prepare the wind speed simulation program WVFS with spatial correlation into consideration, thus generating aerodynamic coefficients of iced conductor at different wind attack angles as well as wind speed time series at tower-line nodes. According to the finite element model of continuous multi-conductors and the aerodynamic force- wind attack angle curve, the explicit integration is applied for numerical solution of galloping of iced conductor.

Studies on Galloping of Iced Conductor Based on Tower-Line Coupling System – Mechanic Model and Intial Shape

A nonlinear finite element model of transmission tower-line coupling system including transmissions, towers and insulators is established based on ANSYS in this paper. Based on the second development at the ANSYS computing platform, finite element model of a Tower-Line Coupling system was established. The approach is applied to study intial shape of Tower-Line Coupling System. With the comparison with classical test cases, the approach was validated, performing high computing efficiency.

Effects of Ice Thickness on the Aerodynamic Characteristics of Crescent Shape Iced Conductors

Aerodynamic characteristics of iced conductors were investigated by the wind tunnel test. Under the homogeneous turbulence of 5% intensity, aerodynamic force coefficients of single and bundled conductors were obtained at wind angles of 0°~180°. The variation patterns of aerodynamic forces on the iced conductors with respect to wind angels of attack were systematically studied for the ice thickness of 0.25, 0.5, 0.75 and 1 times of the conductor diameter. The difference of aerodynamic force characteristics for single and bundled conductors were identified and discussed. Based on the Den Hartog and Nigol’s mechanisms of galloping, the wind angle ranges sensitive to galloping were analyzed. The results show that lift and torsion force coefficients reach peak values at wind angles of 15°~20°. For bundled conductors, lift force curve is approximately agreed with the curve of single conductor. Drag force coefficients were smaller than these of single conductor at some wind angles. There are noticeably differences of torsion coefficients existed between bundled conductors and single conductor. According to two classical galloping mechanisms, wind angles of 15°~30°are critical for the galloping of iced conductors with crescent shapes.

Comparative Analysis of Dynamic Characteristics under Two Iced Conductor Galloping Models

Considering strongly nonlinear characteristic of iced conductor rotating around its center of mass in the wind-deviation plane, two dynamic equations are constructed by using Den. Hartog criterion and O. Nigol criterion, and galloping characteristics between them are studied, which can provide references for constructing correct iced conductor galloping models. By comparative analysis of two models, the vibration frequency of O. Nigol model is slightly higher than that of Den. Hartog model, and the amplitude of O. Nigol model is smaller. Then the stability of iced conductor galloping and the effects of parameters on galloping amplitude are discussed, from which can conclude that the trends of two models varying with parameters are basically identical. But for numerical, O. Nigol model is more accurate.

Nonlinear Numerical Simulation of Iced Conductor Galloping

A two-node cable element which the axial torsion and geometrical nonlinear were considered was developed based on the update Lagrange formulation, and a model of multi-span transmission line for galloping analysis was established. A nonlinear numerical simulation of single iced conductor galloping was proposed. Using computational fluid dynamic, the aerodynamic coefficient of iced conductor with different wind attack angle was simulated. According to the finite element model of multi-span transmission line and aerodynamic coefficient curve, the galloping of iced conductor through the method of fourth-ordered Runge-Kutta method was presented. By the comparison with the classical examples, the results indicated that the presented method are efficient and reliable.