大跨越导线动张力计算和模型实验

为正确认识塔线耦合力等效应理论基础的导线线端动张力,保障线路安全运行的工程需要,在考虑导线初始垂度和抗拉刚度情况下,建立了导线自由振动的非线性微分方程,用连续化超越函数解法,将导线自由振动曲线形式分为正对称和反对称两类模态分别进行模态分析,得出导线动张力成分仅由在平面内对称模态振动引起。将导线不平衡合力对各阶正对称模态幅值求导后为零,联立后求解,即可得到各阶正对称模态幅值,使叠加后的正对称模态与导线实际振动更逼近。将导线在平面正对称基本振型参数规一化后,推导出了导线线端动张力的近似计算公式。对某实际工程的近似公式计算结果与气动弹性模型实验数据对比分析的一致结论说明了动张力近似公式计算结果准确,导线振动过程中线内动张力与初始张力数量级相同。因此,可得出这样结论,导线在实际振动过程中,线端张力变化很大,尤其导线产生低频大振幅舞动时,应慎重考虑由此引起的导线首先失效隐患。

Model Experiment and Analysis of Dynamic Tension of Long Span Transmission Line

Considering the original sag and tensile stiffness of the transmission line system,the nonlinear differential equation of the line's free libration is deduced.The line's in-plane free vibration curve shape of two types modes is composed,i.e.the symmetrical mode and the antisymmetric mode,which are gotten by the continuous transcendental equation method,and the model analysis is processed respectively.At the same time,the dynamic tension of the line's end is only produced by the symmetrical in-plane mode.Assumed that the first-order derivative of the imbalance resultant force along the whole line with respect to the limiting value of each symmetrical in-plane vibration mode was zero,the simultaneous equations are formed,then the limiting values are deduced by the equations.The technique insures that the mode superposition was very approached the line's actual libration.Then the simplified formula of line's dynamic tension is constructed,which is gotten by the normalized parameters of the line's symmetrical modal shape when it vibrates freely in plane.At last,the contrast analysis is carried out between the results about one actual works by the proposed method and the data of aero elastic model experiment.The conclusion illuminates that the proposed method is accurate,and the order of magnitude of the line's dynamic tension is the same as the original tension.So the markedly change of tension of the true vibration line should be taken into account,especially the galloping line,otherwise it would induce the latent disaster of the lead firstly.