جلوگیری از خط انتقال یورتمه رفتن طراحی شده توسط انطباق پشتیبانی
Abstract: Galloping is a large amplitude, low frequency oscillation induced by aerodynamic forces. It is often caused by the accumulation of ice on the transmission line which in turn modifies the cross sectional shape of the conductor as well as the aerodynamic forces. The effect of suspension stiffness on galloping amplitude was investigated by testing of twenty-five pairs of suspension supports with various horizontal and vertical stiffnesses. A dynamic model of galloping motion was simulated by the finite difference method. The experiments were concentrated on conventional galloping which satisfies the Den Hartog criterion. Ice on the conductor was simulated using aluminum and wooden \"D\"-shaped blocks. For each combination of horizontal and vertical stiffness, a scale experimental transmission line galloping test was carried out at six different values of tension in the conductor. A data acquisition system was used to record midspan displacement and support forces. The frequency response of the initial excitation was obtained by performing a Fast Fourier Transform on the displacement data. The galloping profile was shown by using displacement cross plot at midspan. The Root Mean Square amplitude and the Fast Fourier Transform were computed for longer term galloping behavior. The experimental results showed the amplitude of galloping can be reduced to half or one quarter by choosing the proper suspension stiffness. Detuning (nonharmonic motion) was always found at lower tension in the cable. The vertical and horizontal displacement motion of conventional galloping was either in phase or 180 degrees out of phase. The results of experiment were compared with simulation model and agreed in the range of angle of attack which produced galloping and in the decrease in galloping amplitude resulting from increasing cable tension at higher cable tension. Although the results of the experiment and simulation were similar, the amplitude of the galloping produced by simulation was much larger than that recorded in the experiment. It is believed that the large difference was due to complicated wave interaction at the boundary in the experiment and simplifying assumption of constant initial angle of attack used in the simulation. The simplifying assumptions were necessary because of limitation of computing resources and integrating method of solving stiff differential equations. However, the results of the experiment and the simulation both show the strong influence of support stiffness on galloping amplitude.