| With the capacity of transmission line expending rapidly, bundle conductors become the best choice of EHV&UHV lines because of its excellent performance such as inhibition of corona and reduction of reaction. But there are some troubles on bundle conductors which have not happened on single ones. Sub-span oscillation is just a unique phenomenon on bundle conductors and endangers overhead conductors and armor clamps. In view of its theory being too lack to require the demand of engineering and design, further study on sub-span oscillation is needed urgently in order to protect transmission line operation safely.A series of studies on sub-span oscillation is taken in this paper. Starting with the essence of sub-span oscillation, ideal model has been set up and the downstream conductor’ coefficients has been gained. Then put the coefficients on vibrator’s2D model to study conductor’s dynamic characteristics and vibration amplitude when oscillation happens. The determination of sub-span is brought forward to control the oscillation. Several aspects about specific content are as follows:The problem of conductor’s air round flow is investigated and ideal model, from which the coefficients of downstream conductor is got, is set up. The ideal model directly demonstrated the phenomenon of sub-span oscillation while the gotten coefficients as known conditions are useful for subsequent study.Two dimensional vibrator’s2D model is founded. And it has been calculated and analyzed in details to research its dynamic and vibrant characteristics. Feasible measures are proposed to suppress it based on the oscillation described here.Reasonable arrangement of sub-span decreases conductors’ oscillation. The determination of the maximum sub-span based on conductor’ s transverse stiffness and the end sub-span based on conductor’ s self-rotation-resetting property is discussed in Part4, which applied theoretical basis and calculative formula. |
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