大跨越导线在局部激励下微风振动的波动特性

Response characteristics for aeolian vibration of long-span conductors under local excitation

微风振动常造成架空导线疲劳断股断线、金具脱落等破坏。考虑大跨越导线所处风场的切变特性,采用局部激励模型研究大跨越导线的微风振动机理,建立了长柔导线在档内任意局部位置激励下的动力学模型,基于导线系统的小阻尼特性,得到了局部周期激励下长柔导线波动的格林函数解;依据振动波沿展向的衰减特性,将导线内的波动过程分为驻波振动、行波振动以及驻波和行波的混合振动等三种类型;分析系统各参数对波动特性的影响,提出并讨论导线波动类型发生的判别参数(nζ);分析激励位置对架空导线波动特性的影响规律。结果表明:判别参数越小,系统振动波越易表现出单模态驻波形态,随着判别参数的增大,系统振动波会表现出无限长结构的行波特性;激励位置作用在某一阶振动波的理想波峰时形成的振动波幅值最大,作用在理想波节位置时难以形成显著的振动波;实际导线的振动波是驻波和行波的叠加波。

Aeolian vibrations often occur on transmission lines,which can result in fatigue damage to the conductors and metal fittings.In order to understand the mechanism of aeolian vibrations of long span conductors,a linear model of the forced vibration of finitely long damped tensioned strings under single-point harmonic excitation is established,and the corresponding Green′s function solution of steady state response is derived.Based on the qualitative analysis of the parameters affecting the response type of the system,the discriminant parameter of the control response type and its expression are proposed.The spatial distribution characteristics and temporal and spatial evolution characteristics of wave responses under different discriminatory parameters are further analyzed.The relationship between the position of excitation and the amplitude of vibration wave is discussed.The results show that the discriminant parameter which determines whether the conductor acts like infinite conductor or not is the product nζ,where n is the mode number of the highest resonantly excited mode in the system.When nζis small then single mode resonant response will dominate the total response.When nζis large,except when excited near an end,the conductor can be considered to behave dynamically as if it were infinite in length.The excitation position has a significant effect on the amplitude of vibration wave.When the excitation position acts on the ideal peak of a certain vibration wave,the amplitude of the vibration wave is the largest,and when the excitation position acts on the ideal node position,it is difficult to form a significant vibration wave.The vibration wave of actual conductor is a mixed wave of standing wave and traveling wave.