Numerical Analysis on Anti-galloping VED of Transmission Lines

Abstract

A 2-DOF model with the coupling of vertical and torsional motions is considered to study galloping of transmission lines in this paper. Based on Lagrange equation, the equation of motion is established. dynamic analysis is obtained by using Newmark-β method in an example. Finally, anti-galloping VED is used to investigate its effect of vibration control. Keywords-transmission lines; galloping; 2-DOF model; anti-galloping VED; numerical analysis I. FOREWORD Galloping of iced transmission line is a typical low-frequency (about 0.1 ~ 3Hz), large amplitude (about 5 ~ 300 times of the diameter of the wire) of the self-excited vibration of gas-solid coupling phenomenon. When galloping, all-speed wire do directional wave undulating movement. Due to large amplitude, long time vibration is easy to cause flashover, seriously causing fitting damage, line tripped, tower failure, etc[1-2]. Since the 1920s, national science and technology workers have carried out extensive research and achieved fruitful results about galloping in the theoretical analysis and experimental verification. In galloping mechanism, Den Hartog wave vertical excitation mechanism[3] of the United States and O. Nigol torsional excitation mechanism[4] of Canadian are still the mainly ones, the studies of other mechanism and anti galloping measures are based on the two theories; In Experiment, wind tunnel test is mainly used to test the aerodynamic coefficients of iced conductors, wind tunnel simulation test of galloping with iced line is considerable difficultly carried out. To study test line is undoubtedly the most direct method for galloping, but the observation time long and expensive. Numerical simulation research has been an important means of galloping problem. Currently, there are single-degree-offreedom model of vertical, 2-dof model of vertical and torsional coupling, as well as 3-dof model of vertical, horizontal and torsional coupling[5] used to study galloping. The 2-dof model, not only taking into account the Den Hartog vertical galloping theory and Nigol torsional galloping theory, but also ignoring the minor horizontal movement, is simple, easy to be carrid out dynamic characteristics analysis for wire. According to statistics, the current anti-galloping devices[6-9] of domestic transmission line include double pendulum anti-galloping device, rotating clamp spacer, phase spacer and so on, they all achieve good anti-galloping effect in practice, they work mostly by changing line structure and parameters. According to mechanism of galloping, whether Den Hartog vertical excitation mode or Nigol torsional excitation mode, galloping inspire is dynamic instability phenomenon caused by negative damping energy accumulation of wire system, so the conductor structural damping is one of the important characteristic parameters of galloping, the source of galloping in the inherent characteristics of the structure. Adding wire damping structure and dissipating wind power of wire system is a fundamental way to inhibit galloping. In this paper, the anti-galloping of VED, with the energy dissipation capability of viscoelastic materials and the TMD effect[10-12], increase the damping of the wire and effectively inhibit galloping of wire. In this paper, the galloping of wire is studied with 2-dof degree of vertical and torsional coupling and Newmark-β dynamic analysis methods, the anti-galloping VED is joined, the mathematical model is proposed, and damping effect is theoretically analyzed. II. 2-DOF MODEL OF THE WIRE A. Dynamic Balance Equation of Wire without Anti-galloping VED The 2-dof model is described by the use of the whole fixed coordinate system Y-O-Z and local moving coordinate system Ya-a-Za, as shown in Figure 1. The origin of Ya-a-Za is located in the center of rotation a, the rotation angle of the moving coordinate system around a is described by t θ . 2015 AASRI International Conference on Industrial Electronics and Applications (IEA 2015) © 2015. The authors Published by Atlantis Press 209