【作者】 杨伦；

【导师】 楼文娟；

【作者基本信息】 浙江大学 ， 结构工程， 2014， 博士

【摘要】 舞动是导线覆冰后在风荷载作用下产生的自激振动。舞动对输电线路危害极大,引起的动张力会造成相间闪络、导/地线断股、间隔棒撕裂等事故。尤其是在特定气象条件下,导线舞动的持续时间可长达几天,从而有可能导致杆塔构件撕裂、失稳甚至倒塔等事故的发生。近年来,随着我国电网规模的迅速发展和恶劣气候的频繁出现,电力系统发生舞动事故的频率和对电力行业的危害程度呈显著增加的趋势,严重威胁着电力能源的正常输送和国民经济的稳定发展。因此,深入开展覆冰输电线路舞动的试验研究和理论分析、完善输电线路抗舞设计方法和提供相关技术支撑和科学依据,有着十分重要的工程意义和经济价值。本文的研究工作主要包括以下几个方面：1.覆冰输电线路静张力对横担作用特征的研究：以在线路覆冰作用下横担严重破坏的转角耐张塔为研究对象,制作大比例输电塔节段模型,并按相似理论设计、加工了覆冰导线模型,对输电塔进行了模拟导线重覆冰状态下的静力加载试验。同时考虑连接偏心、节点板和螺栓长度等细节对构件传力路径的影响,建立了精细化的中横担有限元模型,对静力试验进行全过程的数值模拟,并与关键截面处的荷载-变形特征试验结果进行对比。在此基础上通过非线性屈曲计算,考察了覆冰导线静张力作用下横担的失效模式及薄弱环节。2.输电塔线体系舞动响应和杆塔失效机理的试验研究：以在舞动事故中横担严重破坏的某转角耐张塔研究对象,基于模型动力相似原理,设计制作了弹性边界条件下的大比例输电塔节段模型和能够模拟不同覆冰参数的导线模型,并首次研制开发了模拟覆冰导线舞动的试验加载装置。在此基础上,于试验室条件下再现了导线舞动时的动张力和运动特征,并进行了不同参数下的输电塔线体系舞动试验,研究了覆冰厚度、舞动幅值以及频率对塔线体系响应特征的影响。同时,结合实际线路舞动时的特征参数,于试验室条件下进行了覆冰塔线体系舞动事故的反演,并根据试验测得的构件动应力幅值,计算了输电塔构件在导线舞动作用下的疲劳寿命。最后,综合分析塔线体系舞动试验和疲劳寿命的计算结果,揭示了舞动作用下输电杆塔失效的根本原因。3.覆冰输电线路舞动非线性动力学与双参数分岔分析：建立了考虑竖直向、水平向和扭转向三维非线性耦合效应的连续体覆冰分裂导线舞动方程,并根据Galerkin积分和Routh-Hurwitz稳定性判据准则标识系统在参数空间中的稳定域和非稳定域。在此基础上,选定风速、初始风攻角以及竖向阻尼比为分岔参数,应用中心流形降维方法求解了原系统在平衡点附近的约化系统。通过将分岔参数视为系统状态变量的方式,把含参数的约化系统转化为不含参数的扩张系统,并利用规范形理论分段求解了扩张系统的Hopf分岔规范形,研究了双参数同时变化对导线舞动响应的影响。4.分裂导线舞动非线性数值模拟：基于完全拉格朗日格式,建立了适用于单导线和分裂导线舞动数值模拟的非线性有限元舞动分析方法。采用具有扭转自由度的三节点抛物线索单元离散覆冰单导线。对于覆冰分裂导线,在单导线有限元法的基础上,利用欧拉梁单元模拟间隔棒的运动过程,结合梁节点弯曲自由度缩聚法实现了间隔棒与分裂子导线之间的耦合,并运用随转坐标系求解舞动过程中的梁节点不平衡力。在此基础上,结合覆冰分裂导线气动力测试结果,研究了风场特性、导线覆冰厚度和初始凝冰角对输电线路起舞机理和响应特征的影响。5.三维瞬态风场下覆冰导线舞动数值模拟：根据随机流场生成方法和三维风速功率谱,逐点模拟了覆冰分裂导线周边的脉动风速场,并从瞬态流场的不可压缩特征、风功率谱、时间相关函数以及空间相关系数等统计特征证明了风场模拟方法的有效性和合理性。运用分裂导线舞动非线性有限元法对输电线路在均匀流场、一维脉动风速场和三维瞬态风场下进行了舞动瞬态分析,在此基础上讨论了风速场瞬态效应对舞动响应的作用机制,更多还原

【Abstract】 Galloping of power transmission line is a typical self-excited vibration due to wind action on an ice or wet snow accretion on the electrical conductors. The occurrence of galloping could cause large dynamic tension acting on transmission lines and towers and induce a series of accidents, such as flashover between different interphases, power/ground line and spaceres broken off. Especially during some special climate conditions, several days longer duration of galloping will bring great damage to tower components and even result in whole towers collapse. In recent years, due to the mushroom development of the power grid and frequent appearance of bad weather conditions, the galloping accident frequency and the damage to power system, which severely endanger the transmission of electrical power and stable development of national economy, has been significantly increased. Therefore, it has great engineering significance and economy value to promote the experimental and theoretical investigation on galloping of iced transmission line, improve anti-galloping design method and provide corresponding technical or scientific supports. The following research aspects are included in present paper:1. Study on mechanical features of tower cross arm under static tension of iced conductor:The segmental strain resistant corner tower model with1:4scale whose cross arm has been damaged during ice disaster was made according to similarity relationship, and the corresponding iced-conductor model was also established. Then the static experiment was conducted to simulate the tension of heavy iced-transmission line acting on tower. Meanwhile, the finite element model of middle cross arm was also founded precisely by taking into account the effects of connection eccentric, joint plate and the length of bolts on the force-transfer characteristic of members, then the whole test process was simulated and the comparison with experiment values was also obtained. On this basis, failure mode of cross arm was obtained by using the method of nonlinear bulking analysis.2. Experiment research on dynamic responses of transmission tower-line system and failure mechanism of tower under iced-conductor galloping:Taking a strain resistant corner tower as prototype whose cross arm was seriously damaged under iced-conductor galloping, a tower segmental model with elastic boundary condition and conductor model of different ice thickness were founded on the basis of the similarity theory of dynamic model, and the vibration experimental equipment used to simulate galloping responses of iced-conductor was developed at the first time. Based on that, dynamic tension and vibration features of galloping conductor were reconstructed under the laboratorial conditions. Then galloping experiment of transmission tower line was carried out, the effects of ice thickness, galloping amplitude and frequency on dynamic response of transmission tower-line system were discussed. According to thickness of ice and vibration amplitude obtained by field testing, the dynamic experiment of transmission tower-line was carried out under conductor galloping. Combining with the experimental results of dynamic stress, fatigue life of tower member was estimated. Finally, the real reason for tower collapse under iced-conductor galloping was determined based on the results of tower-line galloping experiment and tower member’s fatigue life.3. Nonlinear dynamics and double parametric bifurcation analysis of iced transmission line:A three dimensional galloping model for iced-bundle conductor, considering non-linear coupling effects of vertical, horizontal and torsional direction, was approached to investigate the action mechanism of system parameters in stability and nonlinear dynamic responses based on Lagrange equation. Galerkin integral method and Routh-Hurwitz criterion were introduced to obtain stable and unstable region in parametric space. Choose wind velocity, initial wind attack angle and vertical damping ratio as bifurcation parameters, the reduced equations in the vicinity of bifurcation point were determined through central manifold theory. By regarding bifurcation parameters as state variables, the reduced system with parameters were converted to extended system without parameters, and then Hopf bifurcation equations sectional solution were calculated with the help of normal form theory in polar coordinates. Based on that, the features of simultaneous varieties of galloping in double parametric space were discussed in detail. 4. Nonlinear numerical simulation for iced bundle conductor galloping:A dynamic nonlinear numerical model with the consideration of aerodynamic and geometric nonlinearities was established to simulate the galloping behavior of iced single and bundled conductors with arbitrary number of sub conductors on the basis of Total Lagrange finite element method. The three-node parabolic cable element with torsional degree of freedom was applied to discrete the single conductor. As for bundled conductor, the Euler beam element added into sub-conductors was used to simulate the movement of spacing rod. A high effective bending degree of freedom reduced method was introduced to simulate the coupling effects of cable and beam element. Meanwhile, the unbalance force vectors of beam element during galloping process were derived precisely by employing co-rotational coordinate system method. Finally, based on the aerodynamic force of iced-conductor with crescent shape obtained by wind tunnel experiment, the impact of turbulence, ice thickness and initial ice-coating angle on conductor galloping mechanism and dynamic responses were investigated.5. Numerical simulation of iced-conductor galloping in three dimensional fluctuating wind field:According to random flow generation method and three dimensional wind power spectral density function, the fluctuating wind field around iced transmission line was simulated point by point. Meanwhile, the statistical characteristics of fluctuating wind field, such as divergence free, power spectral density function, temporal correlation function and spatial correlation coefficients, were verified to illustrate the availability and reliability of presented wind filed simulating method. Then the galloping responses of iced bundled-conductor were determined by applying nonlinear finite element method in uniform flow, one dimensional and three dimensional fluctuating wind field. Based on that, the impact of turbulence on transmission line galloping was discussed in detail.更多还原