Aeolian Vibration Research Articles

Arrangement Method of Vibration Dampers Considering Frequency Response Physical Characteristics and Stiffness of Conductor

In order to study the calculation method of installation distance of vibration dampers with higher precision, so as to maximize its anti-vibration performance on the conductor. The arrangement method of dampers based on the frequency response characteristics of conductors is proposed, the dynamic model of conductor considering stiffness is established. The model is solved by finite difference method, the natural frequency and vibration mode of conductor in case of Aeolian vibration are obtained, and the wavelength of conductor vibration is obtained according to its mode, so as to calculate the installation distance of vibration dampers. The calculation results of the new method are compared with those of the traditional method, which proves the advantage of the new method in calculation accuracy. The new method has a good effect on improving the calculation accuracy of the installation distance of the vibration dampers on the conductors, which is greatly influenced by its stiffness. At the same time, the frequency response of the conductor should be considered as much as possible in the calculation of the installation distance of the damper.

Experimental investigation of self-damping characteristics of the ACSR Beresford and TERN transmission line conductors using log-decrement and quality factor methods

This work considered the experimental investigation of self-damping characteristics of ACSR Beresford and TERN transmission line conductors using the free and forced vibration techniques. When subjected to a load, self-damping is the power dissipated per unit length of the conductor as it vibrates. ACSR Beresford and TERN conductors are the two most commonly used conductors in the South African transmission network. The paper has revealed that for all the tests, the damping factors for the forced vibration on the TERN conductor was ζ ≤ 0.0307, and for the free vibration was, ζ ≤ 0.057, whereas the damping factors for the ACSR Beresford (forced vibration) were found to be ζ ≤ 0.0103, and for the ACSR Beresford (free vibration) were found to be ζ ≤ 0.056.The damping factors obtained in both conductor-tests were not sufficient to suppress Aeolian vibrations. Results obtained by Mokeretla (2011), that the internal self-damping of TERN transmission lines could not suppress Aeolian vibrations, have been confirmed, due to the damping values being much less than critical damping (ζ ≪ 1). An additional conductor was tested, the ACSR Beresford conductor, whose self-damping factor was also not sufficient to suppress Aeolian vibration.

A structural health monitoring system of the overhead transmission line conductor

Transmission lines are affected by aeolian vibration, sandstorms and acid rain, which cause structural damage and eventually lead to line breaking accidents. In this paper, the structural health monitoring technology of conductors is researched, and a structural monitoring system for conductors is designed. First, based on the structure of the ACSR (Aluminum Conductor Steel Reinforced) conductor and the dynamic equation, the relation between the natural frequencies and the structure of the conductor is obtained. Then, an online health monitoring system of the conductor structure is proposed, and key issues, such as the power supply solution of sensors, data preprocessing technology, multiple-sensor synchronization method, are analyzed in detail. Finally, the structural health monitoring of overhead transmission lines designed in this paper is tested on 110-kV experimental transmission lines. The experimental results show that from the system proposed the operation parameters of the conductors can be well obtained.

The approximate calculation of the natural frequencies of a Stockbridge type vibration damper and analysis of natural frequencies' sensitivity to the structural parameters

Abstract. Vibration damper is widely used in overhead transmission lines to alleviate aeolian vibration. Its natural frequencies are important parameters for a vibration damper. In this paper, the approximate calculation formulas of natural frequencies of the one-side subsystem of a Stockbridge type vibration damper were derived and the design sensitivity analysis of the natural frequencies was studied using partial differential equations with respect to each concerned parameter including the length of the steel strand, the mass of the counterweight, the eccentric distance, and the radius of gyration of the counterweight. Through a case study that considered a variation of up to ±30 % in the values of the design parameters, the exact calculation and approximate calculation results of the natural frequencies were analysed, and the sensitivity of the vibration damper's natural frequencies to the design parameters was studied. The results show that, within the range of the parameters used in this study, the approximately calculated first-order frequency is lower than the exact values, whereas the approximately calculated second-order frequency is larger than the exact values. The sensitivity analysis indicates that the first-order frequency is highly sensitive to the steel strand's length, whereas it is moderately sensitive to the counterweight's mass and slightly sensitive to the eccentric distance and the gyration radius of the counterweight; the second-order frequency is highly sensitive to the steel strand's length and the gyration radius of the counterweight, moderately sensitive to the counterweight's mass, and slightly sensitive to the eccentric distance. It will provide theoretical guidance and approximate analysis method in engineering for the design of the vibration damper.

Dynamic analysis of electrical vibration absorbers for suspended cables

The present research proposes two vibration control techniques for attenuating vibration of laboratory-scale suspended cables. The technique is applied to resolve the problems of such high-frequency vibrations as the aeolian vibration. The vibration control device involves an absorber driven by a motor, and the dynamics of the controlled system is investigated numerically considering practical problems. Particular attention is paid to backlash at the driving that influences the effectiveness of control significantly, and to the time response of the controlled system that indicates how quickly the vibration decays after a change in the excitation. One of the proposed controllers involves the implementation of PID technique that enables the significant reduction in the value of cable displacement and acceleration during aeolian vibration, compared to the conventional vibration absorber. An extensive controller has also been proposed based on estimation of cable vibration frequency. The dynamic performance of the controllers is simulated using Simulink. Results also reveals the limitations in the control due to a practical problem like backlash. The main practical benefit from the study is that it provides information about the advantages and disadvantages of the control methodologies, and recommendation may be done for their application without building the controlled system.

Study of structural-thermal characteristics of electrified conductors under aeolian vibration

High-voltage transmission lines are featured by electrical and structural properties. Current studies on aeolian vibration of transmission lines focus primarily on structural responses of unenergized conductors. However, moderate aeolian vibration can also enhance the convection heat transfer capability of a transmission line, which improves the steady current-carrying capacity. In this paper, a fluid-structure interaction (FSI) model is established to study the structural thermal characteristics of overhead electrified aluminum conductor steel-reinforced cable (ACSR) conductors. Moreover, the fatigue damage of the energized conductor is analyzed under operational conditions. Results show that there is considerable influence from aeolian vibration on the current-carrying capacity of energized conductors. Compared with the nonelectrical conductors, aeolian vibration can enhance the convective heat transfer effect of energized conductors. Additionally, fatigue life of electrified transmission lines is larger than that of nonelectrical conductors under aeolian vibration. The developed structure-fluid-thermal model can be used to aid design and operation optimization of transmission lines.

Corrigendum to “An enhanced unified model for the self-damping of stranded cables under aeolian vibrations” [INDAER 182 (2018) 72–86

Corrigendum to “An enhanced unified model for the self-damping of stranded cables under aeolian vibrations” [INDAER 182 (2018) 72–86

On the Euler-Lagrange formalism to compute power line bundle conductors subject to aeolian vibrations

Analytical models of aeolian vibrations for both twin and quad bundle conductors are summarized in this paper. These analytical models are defined by equations of motion and developed using the Euler-Lagrange formalism. They describe the behavior of bundle conductors under combined effects. The generated swinging, and flexural and torsional motion are addressed. To simplify the complexity of the calculus during the development of the analytical models, several assumptions are made: (i) aeolian vibrations remain in the range of small oscillations; (ii) acceleration is constant at each frequency; and (iii) the Kelvin-Voight rheological model is considered for the vertical and horizontal stiffness in the spacer-damper. These analytical models are compared and validated by means of numerical simulations using the results from indoor experiments on an overhead transmission line-span with quad-bundle conductors. This has only one spacer-damper attached at its mid-span. The comparisons show good agreement between experiments and numerical simulations in the rigid mode, and an insignificant discrepancy in the damping mode. Finally, the performance of twin spacer-dampers in terms of dissipating wind-induced power in transmission line twin-bundled conductors is assessed and compared with quad bundles through developed analytical models, and the physical significance are highlighted.

Fatigue Evaluation of All Aluminium Alloy Conductors Fitted With Elastomeric and Metallic Suspension Clamps

Overhead conductors for transmission lines are subjected to cyclic loading due to Aeolian vibration which can lead to the failure of their wires. One of the most critical transmission power line points where fatigue failure occurs is the vicinity of the assembly consisting of the conductor and the suspension clamp. This work evaluates the fatigue life of assemblies made by two types of conductors, i.e., All Aluminium Alloy Conductor (AAAC) 1120 and 6201. Furthermore, metallic and elastomeric clamps are examined. Based on the generated S-N and <inline-formula><tex-math notation="LaTeX">${\boldsymbol{f}}{{\boldsymbol{y}}_{{\boldsymbol{max}}}}$</tex-math></inline-formula>-N graphs, it was proved that the assembly AAAC 1120 with elastomeric clamp presented a better fatigue performance than the other three assemblies. Additionally, the change in fatigue life was investigated, failure and contact marks analyses were also performed on all samples after the fatigue test with respect to the conductor layer where the failure occurred as well as the types of break and the position of wires&#x2019; break (whether radial and longitudinal position).

Characteristics of the asymmetric Stockbridge damper

The Stockbridge damper (tuned mass absorber) is used on overhead transmission power lines to suppress wind-induced vibrations. These power lines get exposed to various types of wind motions that cause them to vibrate and this causes fatigue failure at the suspension clamp where the maximum stress occurs. Aeolian vibration is the most common wind motion that causes fatigue and eventually, failure to transmission lines. This paper presents the study of an asymmetric Stockbridge damper. A set of experiments were conducted on the damper according to the Institute of Electrical and Electronics Engineers (IEEE) 664 standards to evaluate the characteristics of the asymmetric Stockbridge damper. The results obtained revealed that the asymmetric damper is four degrees of freedom. The results also revealed a relationship between the mass and the magnitude of the resonance frequency.

Aeolian Vibration Control of Power Transmission Line Using Stockbridge Type Dampers — A Review

Due to its inherent low damping, a power transmission line is prone to wind induced vibration. Vibration control is needed to suppress the aeolian vibration of the transmission-line to reduce the fatigue and to extend its service life. Though patented in 1928, more than 90 years ago, the Stockbridge damper or its variants are still commonly used for vibration suppression of conductors in modern day power transmission systems because of their advantages of simple structure, low cost, reliable operation and effective vibration suppression. This paper offers a comprehensive review of the development, modeling, analysis, and design of the Stockbridge-type dampers and their applications in Aeolian vibration control of power transmission lines. A Stock bridge-type damper is a dumbbell-shaped device that consists of a short messenger cable with two masses at the ends and a clamp at the middle to attach to a conductor. The friction among the strands in the messenger cable dissipations energy. A Stock bridge-type damper is essentially a tuned mass damper. For the modeling of a Stockbridge damper alone, the classis linear mechanics analysis, the nonlinear analysis, and finite element method (FEM) are reviewed. For the modeling of the combined damper and conductor system, this paper mainly reviews the Energy Balance Principle (EBP) that is relatively easy to use and can obtain the energy dissipated by the damper. Two important design issues, the damper parameter sensitivity analysis and damper location optimization, are discussed in this paper. This paper also briefly reviews the experimentation and fatigue related to a Stockbridge damper. In addition, this paper provides an outlook of future development, analysis, and application of Stockbridge-type dampers for conductor vibration control.

Spider-Web-Inspired PM0.3 Filters Based on Self-Sustained Electrostatic Nanostructured Networks.

Particulate matter (PM) pollution has become a serious public health issue, especially with outbreaks of emerging infectious diseases. However, most present filters are bulky, opaque, and show low‐efficiency PM0.3/pathogen interception and inevitable trade‐off between PM removal and air permeability. Here, a unique electrospraying–netting technique is used to create spider‐web‐inspired network generator (SWING) air filters. Manipulation of the dynamic of the Taylor cone and phase separation of its ejected droplets enable the generation of 2D self‐charging nanostructured networks on a large scale. The resultant SWING filters show exceptional long‐range electrostatic property driven by aeolian vibration, enabling self‐sustained PM adhesion. Combined with their Steiner‐tree‐structured pores (size 200–300 nm) consisting of nanowires (diameter 12 nm), the SWING filters exhibit high efficiency (>99.995% PM0.3 removal), low air resistance (<0.09% atmosphere pressure), high transparency (>82%), and remarkable bioprotective activity for biohazard pathogens. This work may shed light on designing new fibrous materials for environmental and energy applications.

Aeolian vibration‐based structural health monitoring system for transmission line conductors

The transmission line in a power network is similar to a blood vessel. Any disconnection ultimately affects the transmission of electrical energy, and broken strands and detachment of the fittings are early signs of disconnection. Because aeolian vibration occurs on almost all conductors, an aeolian vibration-based structural health-monitoring technology for transmission lines is proposed. First, the influence of strand breakage and detachment of the fittings on the natural frequency of the conductor is described, and the influence of temperature changes on the natural frequency is discussed from the two aspects of the temperature-dependent elastic modulus and temperature-dependent winding angle. Second, we conducted a vibration experiment and found the law of natural frequency variation caused by broken strands, detachment of the fittings, and temperature changes. Finally, we conducted a field test to measure the conductor vibration on a 110-kV transmission line. The results show that the natural frequency can be calculated multiple times by the stochastic subspace identification method, and the calculation results are consistent. After a period of measurement, the natural frequency variation is analyzed. Further, how to determine the structural health of the conductor from the natural frequency measured by the technique under actual operating conditions is explained.

Vibration Analysis of FR-2 Damper Based on ANSYS

The finite element model of FR-2 damper is established, and its natural frequency is gained by calculating. The finite element model of the wire is established, and the first-order natural frequency and mode shape are gained by calculating. The feasibility of the model is verified by comparison with theoretical calculation results. The aeolian vibration of the single-wire system and the FR-2 damper-wire system were simulated and their results were compared. The concept of vibration suppression rate was proposed to measure the suppression effect of the damper on the wire vibration.

A multi-scale strategy to predict fretting-fatigue endurance of overhead conductors

Abstract Overhead conductors enduring aeolian vibrations are subjected to fretting fatigue damage. To predict the fretting fatigue cracking risk along the conductor-clamp assembly involving a multitude of crossed-strands contacts, a multi-scale analysis is considered. First, a global model provides the spatial distribution of normal, tangential and fatigue loadings for every contact. “Specific” loading cases were simulated using a local FEM model involving a Crossland fatigue stress analysis and a critical distance approach to correct the stress-gradient effects. Mono-contact fretting fatigue experiments were then performed reproducing the exact same loading cases. The comparison between numerical predictions and experimental results showed that a very good prediction of crack-nucleation is achieved using this strategy. However, total failures were not systematically observed. It is believed to be related to the manufacturing process. Wire drawing induces a longitudinal microstructure which promotes cracks with a low diving angle, rather than cracks propagating directly into the bulk. 3D-surface-crack simulations confirm a crack arrest phenomenon induced by the contact-induced compressive stress field.

Failure analysis of aluminum wires in all aluminum alloy conductors -AAAC

Aeolian vibration can cause failure by fatigue in electric conductors and, in some cases, possible blackout. In this study, wires extracted from two cables (A and B) made of 6201 aluminum alloy were tested under fatigue. These tests were carried out aiming to evaluate causes of differences observed on fatigue resistance of the two cables, manufactured with the same chemical composition and, apparently, subjected to the same heat treatment (T81). Wires extracted from cable “A” exhibited lower fatigue life than wires of cable “B”. Scanning electron microscopy analyses of fractured wire surfaces demonstrated that failures were caused by fretting fatigue. Images and analyses using transmission electron microscopy and energy-dispersive spectroscopy demonstrated a lower concentration of Mg2Si hardening precipitates and appreciable concentration of plate-shaped β-Al5FeSi phases in cable “A” wires. The lower fatigue resistance of cable “A” wires compared to those of cable “B” are related to inefficient heat treatment applied to cable “A” and existing iron impurities possible originated from raw materials used during the manufacturing process of this conductor. The inadequate aging step of heat treatment gives rise to fewer hardening Mg2Si precipitates. This effect added to existing iron impurities shortened the mechanical properties of cable “A” and, thereby, its fatigue life, when compared to cable “B”.

Aeolian Vibration Control Measures for JL/G1A-400/35-48/7 Conductors

Aeolian vibration control measures for JL/G1A-400/35-48/7 conductors were studied with the energy balance method. The results show that the dynamic bending strain of the JL/G1A-400/35-48/7 conductors with FR dampers is much smaller than the conductor itself under a tension level of 25% RTS, but the dynamic bending strain of the conductors exceeded 120×l0-6 when vibration frequencies are between 30 Hz and 40 Hz and additional FR dampers have no obvious effect. The festoon wire dampers have very good energy dissipation capacity within wide frequencies. The Bate wire dampers were eventually designed as combinations of a 1.2 m single festoon wire dampers, which could reduce the dynamic bending strain of the JL/G1A-400/35-48/7 conductors between 30Hz and 40 Hz. The Bate wire dampers combined with FR dampers could respond to most of the frequencies experienced over the range of wind speeds causing vibration, and keep the dynamic bending strain of the JL/G1A-400/35-48/7 conductors under the required standard, which provides a reference for research and construction of UHV engineering projects.

Study on aeolian vibration suppression schemes for large crossing span of ultra-high-voltage eight-bundle conductors

Ultra-high-voltage transmission line is prone to severely aeolian vibration, especially for the large crossing span. However, few studies were conducted previously, as a result of high nonlinearity...

Analysis of Aeolian Vibrations of Transmission Line Conductors and Extraction of Damper Optimal Placement with a Comprehensive Methodology

Energy balance method is an effective and simple method which is used in the amplitude calculation of Aeolian vibration in transmission lines with Stockbridge damper. However, the accuracy of the results obtained by this method, heavily depends on the assumed mode shapes of the conductor vibration. In this study, by considering an appropriate model for the conductor vibration, a comprehensive methodology is presented to calculate the steady-state vibration amplitude of a conductor with arbitrary number of dampers. In this proposed method, the effects of traveling waves, variations of amplitude and phase, boundary conditions (finite length of the conductor), as well as the effect of number, location and impedance of the dampers are taken into account. Natural frequencies, damping rates and complex mode shapes are also obtained from forming and solving the nonlinear eigenvalue problem. Using this method, the effects of the damper placement on the vibration amplitude and bending strain are examined to achieve an optimum damper location. The comparison of the obtained values shows that considering the above parameters has a significant effect on the accuracy of the results.

Multi-parametric optimizations for power dissipation characteristics of Stockbridge dampers based on probability distribution of wind speed

• Random excitation model of the Stockbridge dampers. • Modeling of the mathematical expectation of power dissipation for the Stockbridge dampers. • Optimization of the multi-structure parameters for structural parameters. Power dissipation characteristics of Stockbridge dampers (SD) is one of the important indexes in anti-vibration work of transmission line. The study focuses on the optimization of the SD's power dissipation characteristics under the effect of multi-structure parameter coupling. The aeolian vibration of overhead transmission lines is uncertain and random in stochastic dynamics. According to Strouhal formula, the relationship between the vibration frequency of transmission lines and wind speed can be found out. Based on the Weibull wind speed probability distribution, the probability density function of the transmission line conductor and damper coupling system vibration frequency is derived. The SD is considered as a typical 2-dimension of stochastic dynamical system. Based on the random process generated by the power dissipation of the SD, the characteristics of power dissipation and SD's resonant frequencies are analyzed when the multi-structure parameters of the SD are coupled. And the diagrams of the power dissipation at various frequencies are obtained. Based on the probability density function of the vibration frequency of the overhead conductor and damper, the objective function, namely the mathematical expectation of power dissipation ( E ( P D)), of the optimizations for the SD's power dissipation under the coupling of multiple structural parameters is proposed for the first time according to the author's knowledge. Constraint conditions of the optimizations are built by the quantization processing. The energy dissipation characteristics of the dampers can be evaluated by E ( P D), and the power dissipation of SD with different coupled dual structure parameters is optimized based on the proposed method. The optimal values or the optimal value intervals of different coupled dual structure parameters are found, which may provide practical data.