特高压多回输电线环流不平衡及保护原理的研究

Ultra high voltage (UHV) multi-circuit transmission line is an inevitable trend for the development and construction of the power system in China. However, the electromagnetic and electrostatic coupling among the lines and phases of UHV multi-circuit transmission lines is more significant and line parameters show a notable frequency-dependent characteristic, thus the problem of circulating unbalanced current of multi-circuit transmission line is more serious. Considering the great impact of circulating unbalanced current on operation and protection of UHV multi-circuit transmission line, digital and physical simulation technology is going to be researched systematically first. To lay a foundation of simulation and theoretical analysis for the in-depth research of UHV multi-circuit transmission line, this project will explore analysis and calculation methods, which take asymmetry parameters, influences of ground wires and frequency-dependent parameters into consideration, of UHV multi-circuit transmission line under phase coordinate system. On this basis, the causes and the key factors of circulating unbalanced current of multi-circuit transmission line will be studied and the influences of circulating unbalanced current under normal operation and fault condition on power transmission, power loss and main or back-up protection will also be analyzed. Furthermore, this project will research several other aspects including adaptive current differential protection principle considering the impact of frequency-dependent parameters of UHV multi-circuit transmission line, adaptive transverse differential protection principle, which is independent of circulating unbalanced current, with the combination of differential elements and direction elements and new protection principle of multi-circuit transmission line using the differences of circulating unbalanced current between normal operation and fault condition. The research results will provide a theoretical and technical support for the development of UHV power grid and improve the reliability of UHV power grid operation.

特高压多回输电线是我国电网发展与建设的必然选择。特高压多回输电线路之间的电磁与静电耦合关系更加显著，线路参数频变特征明显，多回线内部的环流不平衡问题更加突出。鉴于环流不平衡对特高压多回线运行及保护产生的重要影响，本项目首先对特高压多回线的数字与物理仿真技术进行研究；并探索计及参数不对称、地线影响以及参数频变的相坐标系下的特高压多回线分析计算方法，为特高压多回线领域的深入研究奠定仿真试验和理论分析基础。在此基础上，研究多回线环流不平衡的产生原因及其关键因素；分析正常运行和故障情况下环流不平衡对功率传输、线路损耗以及主后备保护的影响。研究考虑参数频变的特高压多回线自适应电流差动保护原理；研究不受环流影响的、差动元件与方向元件相结合的横差保护新原理；研究利用环流在正常运行和故障时的差异性而实现的多回线保护新原理等。研究成果将为特高压电网的发展提供理论和技术支持，提高特高压电网运行的可靠性。

特高压多回输电线是我国电网发展与建设的必然选择。特高压多回输电线路之间的电磁与静电耦合关系更加显著，线路参数频变特征明显，多回线内部的环流不平衡问题更加突出。鉴于环流不平衡对特高压多回线运行及保护产生的重要影响，本项目以静电、电磁耦合引起的不平衡现象为切入点，研究了计及参数不对称、地线影响以及参数频变的特高压多回线仿真建模及故障分析计算方法。研究了特高压多回线环流不平衡的产生机理，分析了杆塔结构、导线排列等影响环流不平衡分量的关键因素；指出了环流不平衡对特高压多回线功率传输、线损等问题的影响。主要以特高压同塔双回线为例，分析研究了在正常运行和区外相间故障时的线路不平衡度，验证了同塔双回线在不同区外相间故障时的零序不平衡度不同。结合我国超特高压同塔线路的运行现状和出现的问题，进行了实例验证与分析，提出了相应的保护改进方案。提出了计及特高压线路环流不平衡影响的多回线保护原理及改进方案等。此外，本课题也分析了局部同塔输电线路发生故障时的零序电流保护、接地距离保护的影响并给出相应的改进措施。研究成果为特高压电网的发展提供理论和技术支持，有利于提高特高压电网运行的可靠性。结合该项目的研究，培养硕士5名，博士1名，在国际学术期刊、国际会议及国内核心期刊上发表论文8篇，被SCI收录4篇、EI收录6篇、ISTP收录2篇，出版专著1部，获国家发明专利1项。