Numerical Simulation And Parameter Analysis On Galloping Of Bundle Conductors

The galloping of an electrical transmission line is a kind of large amplitude, low frequency, self-excited vibration, which is occurred under action of continuous wind forces. In recent years, as more and more ultra high voltage(UHV) transmission line is built, the security of UHV state grid is widely paid attention. As the six or eight bundle conductors are usually adopt in UHV transmission line, the galloping may be more complicated. Therefore, investigating characteristics of galloping of UHV transmission line under different parameters and tower line system,has theoretical and practical significance in electrical engineering.The static aerodynamic coefficients of the crescent shape iced conductor models varying with angle of wind attack were obtained by wind tunnel test. These results provide the necessary datas to investigate galloping of iced eight bundled conductors. It turns out the turbulence does effect to the thicker crescent shape iced eight bundled conductor, the drag coefficient decreases as the turbulence increases; the lift and torsion moment cofficients increase in some ranges of wind attack angles. In contrast, the the turbulence does effect to thinner crescent shape iced eight bundled conductor.The galloping model of iced eitht bundle conductor was designed and the galloping orbits were got by wind tunnel test. An 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 directionsof the conductors can be defined, the aerodynamic forcesvarying with their motion status can be exerted on the conductors conveniently when ABAQUS is used to simulate galloping of transmission lines. 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, the effect of different damping ration in each direction is discussed. It turns out the galloping mode is not changed with different damping ratio values, but the amplitudes of galloping in each direction are effected different damping ratio values. So it is necessary to consider different damping ratio values in each direction during galloping.Based on this method, the 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, and angles of wind attack is studied. It turns out with increase of wind velocity, galloping mode tends to be more complicated, i.e. more loops may be triggered under higher wind velocity. The galloping mode does not change but vibration amplitude increases with span length. As two-to-one resonance exists, saturation phenomenon and energy exchanges between in-plane and out-of-plane directions are observed, and the galloping orbits are similar to shape of number eight.The numerical simulation method of galloping of iced six bundle conductor in transmission tower-line system is investigated and the dynamic response of displacements, galloping orbit, galloping modes and frequencies are obtained. The numerical simulation results are consistent with those measured on the transmission test line, which verifies the numerical model and simulation method. The finite element model and the numerical method can be employed to investigate galloping behavior and assessment of anti-galloping techniques.Finally, based on the development of cable element, a galloping method considering the electromagnetic force is achieved. The effect of current intensity on galloping behavior is studied under different wind velocities, span lengths and sub-span lengths. It turns out electromagnetic force in small span line does little effect during galloping. As span length increases, the effect of the force on galloping becomes obvious, and may even lead to collisions of two sub-conductors. However, when the wind velocity and current intensity are large enough, the electromagnetic force will be helpful for suppressing galloping.The results of this paper provide necessary experimental data and effective numerical method for UHV transmission line galloping and lay the foundation for anti-galloping of bundle conductors.