【作者】 王昕；

【导师】 楼文娟；

【作者基本信息】 浙江大学 ， 结构工程， 2011， 博士

【摘要】 舞动是输电单根导线或分裂导线在中低风速下呈现出的大幅度低频率的自激振动。近年来我国输电线路建设事业突飞猛进,电压等级和建设规模已跨进世界输电大国的行列,随着我国电网规模的发展和恶劣气象的频繁出现,电网发生舞动事故的频率和危害程度呈明显增加的趋势。深入开展导线舞动理论和防舞的研究,对保证我国输电安全具有十分重要的意义,本文将从覆冰导线气动力特性,覆冰导线气弹模型舞动风洞试验,单导线、分裂导线及输电塔线体系舞动数值仿真及相间间隔棒防舞研究等方面对输电导线舞动理论及防舞方法进行较为精细的深入研究和发展。本文工作主要包括以下几个方面：1.2种覆冰形状单根导线及新月形覆冰分裂导线气动力特性风洞试验研究。针对厚覆冰特(超)高压输电导线,制作了新月形及D形两种典型覆冰断面导线节段模型,在风洞中利用测力天平获得单导线和分裂导线子导线在均匀流和均匀紊流中各风攻角下的气动力特性,研究了气动力系数对攻角的变化规律,以及风场中紊流、子导线干扰对试验结果的影响,根据Den Hartog理论分别计算了各种工况下覆冰导线可能发生舞动的风攻角范围。对于单根导线,结合以往试验结果,研究了两类覆冰冰型的气动力特征,得到了一些共性的规律。另外在风洞中对新月形覆冰导线在均匀流场和均匀紊流场下的表面风压分布进行了测量,进一步研究了其局部风压特性。2.覆冰导线气弹模型的舞动风洞试验研究及气动阻尼识别。采用新月形和D形两种典型覆冰断面的导线节段模型,通过弹簧将节段模型与支架相连,利用弹簧和配重等架设了竖向／扭转频率比可调的覆冰单根或分裂导线气弹模型。在风洞中通过调整风攻角使覆冰导线节段模型舞动,获取了舞动响应时程；并采用与试验模型相对应的计算模型模拟得到相同工况下的舞动结果,验证了基于准定常假设的非线性舞动气动力模型,研究了通过静态气动力系数计算所得舞动响应与试验值之间的差异。利用Hilbert变换对舞动响应进行了气动阻尼识别,与理论值进行了比较,研究了其变化规律及各种因素的影响。3.单根覆冰导线舞动的数值仿真。分别采用基于假定模态的舞动解析模型,以及通过三节点抛物线等参索单元模拟覆冰导线的有限元方法求解单根覆冰导线舞动响应,采用Newmark-β方法结合每个时间步内的Newton-Raphson迭代来求解导线舞动非线性动力方程,给出了导线舞动较为精确的时间积分解,对两种方法的求解结果进行了比较。并利用有限元方法对舞动进行了参数分析,研究了各种线路参数对舞动的影响。模拟了通过绝缘子悬挂的耐张-直线.耐张体系的三跨覆冰导线舞动响应,与单跨两端耐张覆冰导线舞动进行了对比,说明了绝缘子及令跨导线对舞动的影响。4.覆冰分裂导线及输电塔线体系舞动响应的计算。利用有限元方法,用梁单元离散间隔棒,建立任意分裂覆冰导线有限元模型,通过模态分析研究了分裂导线动力特性及其影响因素,计算了四分裂覆冰导线在两种典型覆冰形状下的舞动响应。进一步建立了包含紧凑型直线输电塔架的耐张-直线-耐张三跨三相四分裂输电塔线体系有限元模型,计算了三相线路各跨在不同覆冰条件下的舞动响应,研究了覆冰导线舞动对绝缘子串及输电塔的作用特征,以及脉动风荷载分别作用于输电塔和导线时对舞动的影响。5.相间间隔棒防舞研究。首先给出了各类相间间隔棒的物理模型及其有限元实现方法。针对500kV单回路竖向布置的三相四分裂导线,计算了其在安装不同数量、类型的相间间隔棒后子导线张拉力的增量。对安装有相间间隔棒的线路进行了动力特性分析。最后假定其中某相线路因覆冰产生舞动,比较了该相线路在安装了刚性及柔性两类相间间隔棒前后舞动响应的变化,得到了刚性和柔性相间间隔棒的受力状态,以及不同覆冰形状及风攻角下相间间隔棒的防舞效果。更多还原

【Abstract】 Galloping is a low frequency and large amplitude vibration self-excited by single conductor or bundled conductors under mid/low wind velocity. In recent years, the construction of power transmission lines has witnessed great breakthroughs in China, both the voltage level and the construction scale are first-class around the world. However, with rapid development of the power system and frequent occurrence of extreme weather, the frequency and destruction level tend to increase obviously. Consequently, thorough investigation on conductor galloping theory and anti-galloping techniques is of considerable significance to the safety of power transmission lines. In this paper, delicate study including aerodynamic characteristics of iced conductors, galloping of aeroelastic iced conductor model in wind tunnel, numerical galloping simulation of single conductor, bundled conductors and transmission tower-line system as well as the anti-galloping effects of interphase spacer was carried out to obtain further development in conductor galloping theory and anti-galloping techniques. The paper is mainly focused on the following aspects:1.Wind tunnel test study on aerodynamic characteristics of single conductor and bundled conductors with two typical ice-coating sections. As to ultra high voltage transmission conductors with thick ice-coating, truncated conductor models with crescent and D ice-coating sections were made, the aerodynamic coefficients of single conductor and bundled conductors in uniform flow and homogeneous turbulence flow under different attack angles were measured by force balance in wind tunnel. The variation of aerodynamic coefficients with attack angle has been investigated, and the influence of turbulence in the wind field and interference caused by sub-conductors also has been discussed. Based on Den Hartog theory, the ranges of attack angle in which galloping may occur to iced conductors under various cases were calculated respectively. As to single conductor, combined with former test results, the aerodynamic characteristics of the two ice-coating sections were studied and several general principles are received. Moreover, measurement has been conducted on the surface wind pressure distribution of the crescent iced conductor in two types of wind fields, thus further reflects local wind pressure attributes.2.Wind tunnel study on galloping of aeroelastic iced conductor model and identification of its aerodynamic damping. Made in two typical ice-coating section forms(crescent section and D section), aeroelastic models of single conductor and bundled conductors were connected to brackets with springs. The ratio of vertical and rotational self-vibration frequency of the conductor models can be changed by varying spring stiffness, suspension position and additional weight. Galloping of aeroelastic models are excited and recorded respectively in the wind tunnel under appropriate wind speed and attack angles, futher, galloping responses in test were compared with numerical ones from FEM models based on quasi-steady assumption with static aerodynamic coefficients. Vertical and rotational aerodynamic damping in galloping were identified by Hilbert transform, impacts of various factors as wind speed, attack angle, ratio of vertical and rotational self-vibration frequency, iced profile and number of sub conductors on aerodynamic damping were discussed.3. Numerical approach to galloping of single iced conductor. The response of single iced condutor galloping was simulated respectively by analytical model based on assumed-mode method and finite element model which iced conductor was modeled by a three-node, isoparametric cable element with parabolic shape function, a time marching algorithm using Newmarκ-βmethod in conjunction with Newton-Raphson iteration was utilized to integrate dynamic equilibrium equation involving geometric nonlinearities and nonlinear wind load, and results from two methods were compared. Factors influencing galloping were discussed in detailed by parametric analysis with FEM method. Galloping response of three-spans transmission was also derived and compared with response of single span, impacts of insulators and remote spans were discussed.4. Galloping responses of bundled iced conductors and iced transmission tower-line system. The spacers are simulated by two-node beam elements, thus FEM model of bundled conductors with arbitrary number of sub conductors was established, modal analysis was employed to study dynamic property of four bundled conductors and factors impact on it, galloping of four bundled conductors with two types of ice-coating section were obtained. Futhermore, a three-phase four bundled transmission tower-line system with three spans was modeled, galloping responses of one or all phase were acquired when subjected to fluctuating wind load, dynamic loads on insulators and towers due to galloping conductors were determined, some useful conclusion for designing have been found.5.Study on anti-galloping effect of interphase spacer. Firstly, physical models and their implements in finite element method of various interphase spacers were introduced. Then take a 500kV single-circuit three-phase four bundled transmission line with interphase spacer vertically installed for example, the tension increments in sub-conductors with different number and type of interphase spacers were calculated. Also, modal analysis of the transmission line with interphase spacers was conducted. In the end, suppose a certain phase gallops because of ice-coating, comparative analysis of galloping response before and after installing rigid and flexible interphase spacers were carried out.更多还原