【作者】 肖冬萍；

【导师】 何为；

【作者基本信息】 重庆大学 ， 电气工程， 2009， 博士

【摘要】 为了在更大范围内实现能源优化配置、缓解电力供需紧张状况、减少建设成本、提高输电效率,我国发展特高压电网势在必行。但是,随着公众环保意识的增强,电磁环境问题成为制约特高压交流输电工程发展的一个重要因素。在建设“资源节约型、环境友好型”特高压工程的思想指导下,根据我国国情,正确预测和评估特高压交流线路电磁场强度,提出线路优化设计方案,是工程前期必须深入研究的关键问题。而较之高压、超高压输电线路,特高压在电压等级、线路结构、导线类型、运行环境等方面都有较大差异,原有的一些电磁场计算模型不足以准确评估特高压交流输电线路电磁环境。在这一背景下,本论文以特高压交流输电线路下方工频电场和工频磁场、输电线表面工频电场、电晕辐射电磁场为研究对象,优化模型、改进算法,快速而准确地计算特高压交流输电线路电磁场强度并分析其分布规律和特点,对比研究特高压交流输电线路电磁场的影响因素和屏蔽方案,旨在以本论文研究结果为特高压交流输电线路的优化设计提供建议和参考,以技术数据支撑消除公众对特高压交流输电线电磁污染的误解和恐惧。主要研究成果如下:①基于架空悬链导线特性建立了特高压输电线三维工频电场计算模型,将模拟电荷法和矩量法相结合进行电场数值计算。研究表明三维模型较之传统二维模型能够更准确地反映空间电场分布。对比分析了各种线路结构和导线类型条件下的电场强度,首次定量探讨了档距长度、气象因素对电场的影响。②由传输线理论计算输电线路电流,根据Biot-Savart定律推导出计及弧垂的特高压输电线下三维工频磁场数学模型。通过对各种影响因素,如气象条件、线路结构参数、导线类型的研究,提出了控制工频磁场的输电线路结构优化设计建议。③结合模拟电荷法、矩量法和逐步镜像法求解思想,提出了计及弧垂的特高压输电线表面电场计算优化模型,采用模拟电荷位置寻优算法,提高计算精度。本模型能够精细反映各分裂子导线表面电场的分布规律。通过对比讨论线路结构参数、导线类型、气象条件等因素对表面电场的影响,提出抑制电晕的输电线路结构优化设计建议。④基于电晕电流脉冲特性,根据传输线理论和天线辐射理论,推导出特高压交流线路电晕放电瞬态电磁场计算式,初步研究了电晕辐射场的动态时变特性。定义电晕辐射干扰水平,讨论了辐射干扰水平的影响因素。⑤以架设屏蔽线实现对输电线工频电场的防护,讨论了屏蔽线数目和排列方式对屏蔽效果的影响。以设置金属屏蔽板实现对输电线工频磁场的防护,推导出有限宽平板屏蔽区域磁场计算式,从而能够快速评估屏蔽材料的屏蔽效能;仿真研究了屏蔽系统中金属平板自身物理特性、几何尺寸、输电线路结构与屏蔽效能之间的关系。更多还原

【Abstract】 The development of ultra-high voltage (UHV) electric power grid in China is imperative because it is an effective way to achieve energy distribution optimization in more extensive geographical regions, relieve tense contradiction between electric power supply and demand,reduce construction cost and raise transmission efficiency. However, with the enhancement of public awareness of environmental protection, the electromagnetic environment problem has become a critical restriction for UHV AC transmission project. In order to develop a resource-saving and environment-friendly UHV project based on our own actual national conditions, these are key issues in the prophase of the project to exactly forecast and evaluate the electromagnetic field intensity produced by UHV transmission lines, and propose the transmission lines optimization design. However, some previous methods for calculating the electromagnetic field of transmission lines are not appropriate for UHV any more, because there are distinct differences in the voltage level, the structure, the conductor type and the geographical and meteorological circumstances between extra- and ultra- high voltage transmission lines.This thesis focuses on developing theoretical models and arithmetics to study the power frequency electric field (PFEF) and the power frequency magnetic field (PFMF) under UHV transmission lines, the surface PFEF around bundled conductors and the radiated electromagnetic field of corona discharge. Moreover, the influence factors and protective measures of the electromagnetic field are explored with the aim to provide theoretical basis and reference for UHV transmission lines optimization design and eliminate the public worries.The main contributions of the thesis are as follows:①3D model for calculating the PFEF under UHV transmission lines is proposed on the basis of the character of overhead catenary. The analytical expressions are then derived by combining with charge simulation method (CSM) and the moment method (MOM). The results of simulating and measuring show that the 3D model improves the accuracy with respect of conventional 2D model. The influence of transmission lines’structural parameters and conductor types on the PEFE are analyzed and compared. Especially, the quantitative relationship between the length of span, the meteorological parameters and the electric field intensity are firstly founded. ②The line currents which cause the PFMF under transmission lines are determined by using the transmission line theory. Based on Biot-Savart law, the 3D model for the PFMF under UHV transmission lines with sag are established. The influence factors, such as meteorological conditions, configuration parameters, conductor types, etc, are systematically researched. The results are helpful for lower the PFMF.③Motivated by the main ideas of charge simulation method, the moment method and the successive image method, a modified model is established to calculate the surface PFEF around UHV bundled conductors with sag. The optimum location algorithm for simulating charges is adopted to improve the accuracy. The proposed method can truly describe the electric field intensity and its spatial distribution on the surface of each of the bundled conductors. The study results about the influence factors, such as meteorological conditions, configuration parameters, conductor types, etc, on the surface electric field would be used as reference for the UHV transmission lines optimization design to prevent the corona discharge.④A novel model for the corona radiated electromagnetic field is proposed by taking account of the time varying corona current pulses. Then approximately analytical expressions for the radiated electromagnetic field are derived based on antenna radiation model and uniform transmission line theory. The technique can be used analyze the transient process of the radiated electromagnetic field. The concept of radiated electromagnetic interference (EMI) level is defined and its influence factors also discussed and compared.⑤The shielding lines are effective to weaken the electric field intensity. The thesis analyzes the influence of the number of shielding lines and their position with respect to the transmission lines on the shielding effectiveness. On the other hand, the metal plane is usually used as shield for the PFMF. The algorithm for calculation the PFMF shielded by a finite width plate is presented. The simulation results show that the shielding effectiveness is dependent upon not only the physical properties and the dimension of finite width plate shields, but also the structure of the shields and transmission lines.更多还原