【作者】 陈俊旗；

【导师】 王伟；

【作者基本信息】 哈尔滨工业大学 ， 工程力学， 2011， 博士

【摘要】 随着我国经济的快速发展,能源需求不断加剧,电网建设的投入也越来越大。我国电网事故不断,尤其是2008年初的冰冻天气造成大量杆塔倒塌,严重影响经济运行和正常生活。自立式铁塔作为送电线路的重要组成部分,其经济性及安全性对整个线路有重要影响。对其进行必要的优化设计可以带来明显的经济效益,也可以增强线路的安全性。另外,我国资源分布严重不均,而且近三分之二的国土面积为山地,伴随电网的不断建设,越来越多的线路需要跨越山区。山区风受到微地形的影响,有其特殊的运动规律,而处于山地地形中的输电塔线体系在风荷载下的反应有其本身的特点。其次,山地线路中输电塔覆冰后的受力状态,以及线路脱冰后的反应也有着与平地线路不同的特殊性,需要深入分析。本文具体研究内容如下:第一,提出了对自立式铁塔先进行塔身整体结构的智能选型,然后再对铁塔各部分构件进行选型的铁塔优化设计方法。采用面向对象技术建造了塔身结构的选型实例库,然后基于实例推理技术和数据挖掘理论来对铁塔塔身结构进行知识挖掘,并将现行规范中关于铁塔结构构造方面的规定融入到知识库中,开发了基于实例推理和数据挖掘的塔身结构智能选型方案生成系统。按照上述方法对一500kV自立式铁塔进行了优化设计,并对其进行了真型试验,优化后铁塔自重下降了3%,极限承载能力提高了19%。对20基铁塔进行了优化设计,优化后重量平均降低了4.7%,优化后各杆件受力也更为均匀,承载能力最少增强12%。第二,阐述了山区风的特点,分析了山区平均风速剖面的特性,对山区脉动风的湍流特性进行了介绍,并对中美日三国荷载规范中关于山区风荷载的规定进行了对比分析。当山体坡度较小时,三国规范中的地形影响系数较为接近,随着坡度的增大,中国荷载规范与美日相比地形影响系数的规定更为保守。建立了山区输电塔线体系精细化有限元模型,对其动力特性进行分析,比较了山体高度、宽度对输电塔线体系动力特性的影响,还比较了其与平地线路的差异。随着高差和档距的增大,输电塔线体系相同阶次的自振频率减小。分析了山地地形上的输电塔线体系在风荷载下的动力响应,分别探讨了地面粗糙度、风速、山体高度、山体宽度和来流方向等因素对输电塔线动力响应的影响。随着地面粗糙度的增大,输电塔线体系的风振反应略有减小。随着风速的增加,塔顶位移、绝缘串偏移、导线位移、不平衡张力和支座反力力等均呈现增大趋势。相同风速下,一般是位于山顶的铁塔塔顶位移最大,而位于山腰的绝缘串偏移最大,规范规定的验算山区输电塔不平衡张力的取值偏小。分析表明,支座处竖向反力在风偏角为60°时达到最大值。第三,建立了山区输电塔线体系的覆冰和导线脱冰模型。对山区输电塔线体系在覆冰作用下的反应进行了分析,分析了山体不同位置处输电塔的覆冰承载能力。不均匀覆冰对输电塔的抗风承载能力有重要影响,考虑不均匀覆冰时,山区输电塔的抗风能力有明显下降。分析了山地线路不同脱冰情况下体系的动力反应,分别考虑了不同档脱冰、山体高度和不均匀脱冰等对体系动力反应的影响。脱冰档越靠近山脚,其档中的跳跃越大,引起的相邻档中点位移也越大。位于山腰处的铁塔,两侧导线中当较低档脱冰比较高档脱冰产生的纵向不平衡力更大。位于山顶处的铁塔,脱冰档越靠近山脚,对其产生的纵向不平衡张力越大。更多还原

【Abstract】 With rapid economy development of China, demand of energy has been growing continuously, and more and more capital has been invested into power grid. However, accidents are caused frequently by weakness of power grid which should be attributed to insufficient cognition of working principle of transmission tower. Especially, a large number of towers collapsed because of freezing weather in early 2008. As a result, economic operation and routine life were severely affected. For self-supporting towers are important parts of transmission line system, their economy and security have vital impacts on whole system. Consequently, optimal design of tower can contribute significantly to both economic benefit and security of whole transmission line system. Furthermore, the distribution of resources in China is severly uneven. However, nearly two-third of the land in China is mountainous areas. Hence, more and more transmission lines have to cross mountainous area with continuous construction of power grid. Due to motion of wind in mountainous areas follows special law under impact of micro topography, response of transmission line system in mountainous areas has its own characteristics. Moreover, stress state of iced transmission line systems and their responses after ice shedding in mountainous areas are different from those in flat lands, which result in necessity to conduct deeply research. In this paper, four issues are studied:First of all, the optimal design method for self-supporting transmission tower is put forward, whose procedure is that the tower body form is selected intelligently firstly and then components’types of tower are chosen. The case base of towers is established with application of object-oriented technology. Then, the knowledge of tower body is mined out with case based reasoning technology and data mining. At the same time, the structural regulations of tower in the standard are merged into the knowledge base. So, the intelligent selection system of tower structural scheme based on case reasoning and data mining is explored. A 500kV self-supporting tower is optimized according to above method and a real model test is conducted. Comparison between optimal tower and original tower indicates that weight of optimal tower is decreased by 3% and its ultimate bearing capacity is increased by 19%. Statistical analysis results of 20 optimal towers indicates that the weight is average reduced by 4.7%, the components of the optimal tower are stressed more uniformly and bearing capacity of the tower is savely enhanced 12%.Secondly, the wind characteristics in mountainous areas are researched on. Mean velocity profile and turbulence characteristics of wind in mountainous areas are analyzed. And a comparison is made between the provisions about wind load in mountainous areas in load codes of China, the USA and Japan. The topography factors in the three codes are close to when the hill slope is relatively small. However, the topography factor in China load code is more conservative than USA and Japan as the hill slope increasing.The finite element model of transmission tower-line system(TLS) in mountainous areas is established and its dynamic characteristics are analyzed. Furthermore, the differences of TLS natural frequency with varying of the hill height and width are discussed. These studies verify that the TLS natural frequency at the same order decreases with the increase of hill height and width. The dynamic responses of TLS under wind load in mountainous areas with different roughness, wind velocity, hill hight, hill width and wind direction are presented. As the surface roughness increases, the wind induced vibration responses of TLS decreases slightly. The displacement at tower top, insulator offset, wire displacement, reaction force and unbalanced tension increase with the increase of wind velocity. The top displacement of tower on the hilltop is maximal. However, the offset of insulator which is suspended on the tower located on the hillside is maximal. The unbalanced tension to check the tower in mountainous areas in the code is relative small which is unsafe. The analysis shows that the vertical reaction force reaches the maximum when the wind direction is 60°.Finally, the ice coating and ice shedding model of TLS are established. The capacity of tower carrying ice load which situates on different positions of hill is analyzed. Non-uniform ice coating on wires has a great impact on the TLS capacity of wind resistance. The ability to resistant wind load of TLS decreases evidently when the thickness of ice coating on the wire is non-uniform. Moreover, the dynamic responses of TLS are discussed in different ice shedding situations, taking the different ice shedding span, hill height and non-uniform ice shedding into account. The larger the jumps of the ice shedding span and the adjacent spans are, the closer the ice shedding span is to hill foot. The unbalanced tension of tower locating on the hillside is larger when the ice shedding span is lower in both sides of the tower. The unbalanced tension of tower which locates on the hill summit is larger when the ice shedding span is close to hill foot.更多还原