阻尼变化对脱冰冲击下输电线路动态特性影响

Influence of Damping Variation on the Dynamic Response of Transmission Lines under Ice Shedding Shocks

在初始脱冰冲击下,发生振动的输电线路不仅质量和刚度会随时间变化,而且阻尼也呈现出时变特性,导致系统的动态响应更加复杂,以往对此鲜有研究。通过考虑诱发脱冰效应,给出输电线路系统动力学方程,采用用户自定义"单元生死"子程序实现对系统时变特性的有限元模拟;采用瑞利阻尼模型,系统地研究阻尼率、阻尼取值方式和阻尼矩阵更新方式变化对发生自然脱冰的输电线路动态特性的影响。结果表明,阻尼率和阻尼取值方式变化对系统动态特性的影响明显,阻尼矩阵更新方式对其影响较小;考虑诱发脱冰效应和阻尼的时变特性后,输电线路脱冰振动的幅度显著增大,以往的模拟方法低估脱冰跳跃造成的危害,存在安全隐患,采用所提方法有助于保证输电线路安全。

After initial ice shedding, the mass and stiffness as well as the damping of vibrating transmission lines are all time-varying, which induces more complicated transient dynamic response of the system. However, this problem was scarcely addressed in previous studies. In this paper, considering the ice-shedding induced effect, the equilibrium equations were presented and the time-varying characteristics of the system were modeled by means of finite element analysis with a user-defined element rupture subroutine. The Rayleigh damping model was employed to study the influence of damping ratios, damping computation methods and damping matrix updating methods on the dynamic performance of the transmission lines under the ice-shedding condition. The results indicate that the damping ratios and the damping calculation methods have significant influence on the dynamic response of the system, while the damping matrix updating methods have little influence. The vibration amplitude of the transmission line system increases greatly when the induced ice-shedding effect and the time-varying damping are considered. It can be concluded that the previous modeling methods may underestimate the adverse influence of the ice shedding and the proposed method in this paper can help to ensure the safety of transmission lines.