Numerical Simulation Study On Galloping Of Iced Quad-Bundle Conductors And The New Anti-Galloping Devices

The galloping of an electrical transmission line is characterized by large amplitude, low frequency, self-excited oscillation, which is occurred under action of continuous wind forces. Overhead lines galloping may bring some huge damages such as rupture of conductor and hardware fittings, failure of tower bolt or even collapse of the tower and it is threatening seriously for safe operation of electrical transmission line. Therefore, the studies on the galloping characteristic and anti-galloping of iced bundle conductor behave great significance on theoretical and engineering practice.Fistly, the wind tunnel test project of aerodynamic coefficients'measurement for iced quad bundle conductor was designed. Then, the static aerodynamic coefficients likes life, drag and moment of each sub-conductor of iced bundle conductor varying with attack angle, in the cases of different wind speeds, ice shape and ice thickness, were obtained in wind tunnel. It is observed that the wake interference around sub-conductors on the aerodynamic coefficients is obvious and the curves of aerodynamic coefficients are nearly the same in the case of different wind speeds. Meanwhile, the effect of ice thickness on aerodynamic coefficients is obvious and the aerodynamic coefficients of different ice shapes are obvious difference.The numerical smulation method of galloping of iced conductor is investigated by finite soft ABAQUS. Through the release of the bending degree-of-freedom of Euler beam element and setting the material to be'No Compression', a cable element with torsion degree-of-freedom, which was used to simulate the iced conductor, was obtained. The aerodynamic loads including drag, lift and torque varying with times and attact angle on the iced conductor were applied at each node of the cable elements by means of the user-defined element. The galloping of iced single conductor and iced twin bundle conductor were numerically analyzed to demonstrate the efficiency of the presented method.The effect laws on single span iced quad bundle conductor in cases of various parameters are inverstigated by the presented method of galloping simulation of iced conductor. The galloping of iced quad bundle conductor is discussed by taking into account the wake interference. The results indicate that the galloping amplitudes of iced conductor with taking into account wake interference are larger than those without taking into account wake interference. The galloping of iced quad bundle conductor in different wind speed, ice shape, ice thickness, initial angle of attack and span length are inverstigated. The results provide that galloping amplitude of iced bundle conductor increases with wind speed, ice thickness and span length, galloping amplitude of quad bundle conductor with sector-shaped ice is larger than that of the conductor line with crescent-shaped ice, and it is possible for galloping to happen as the angle of attack locates in the region where the slope of the lift coefficient curve is negative and initial angle of attack greatly affects the occurrence and galloping behavior of iced bundle conductor. Meanwhile, the mode of galloping becomes more complicated in case of longer span length of iced conductor. In addition, the galloping characteristics of iced quad bundle conductor under the action of stochastic wind forces is investigated by numerical method and the results provide that taking into account the steady wind force is enough for the study on galloping of single span iced conductor in case of a certain range of span length.The continuous spans iced quad bundle conductor in cases of different span lengthes and spans are founded, and then the galloping of those are simulated under the action of steady wind force and stochastic wind force respectively. The results show that the galloping modes of continuous spans iced quad bundle conductor are obviously different from those of single span iced quad bundle conductor and the galloping modes of continuous spans iced quad bundle conductor under the action of stochastic wind force are more complicated than those under the action of steady wind force.A new anti-galloping device is presented based on the galloping characteristic of iced bundle conductor. The anti-galloping mechanism of this device is studied, and the optimum design criteria of it are obtained which including increasing the mass of spring mass system, decresing the damping ratio of spring mass system and the value of natural frequency of spring mass system being equal to that of galloping of conductor. The finite element model of a typical section of transmission line including iced conductor and the anti-galloping devices and anti-galloping method are investigated. Then, the anti-galloping schemes for galloping of single span length and continuous spans iced quad bundle conductor are designed respectively based on the results of analysis of displacement spectra. The dynamic response in the case with new anti-galloping device on the single span length and continuous spans iced quad bundle conductor are numerically simulated under the action of steady wind force and stochastic wind force respectively. The results show that the effect of the new anti-galloping device is evident and the device is prospective in the engineering application.