【作者】 张玮；

【导师】 潘贞存；

【作者基本信息】 山东大学 ， 电力系统及其自动化， 2008， 博士

【摘要】 随着“一特三大”电力发展新格局的构建,我国的电网规模日益庞大。大规模的输电网络在提高了系统经济性的同时,也使得系统发生连锁故障的几率大大增加。近年来,在世界范围内发生了多起大规模的停电事故,暴露了电力系统继电保护和安全自动控制方面的许多不足。从对多次大停电事故分析的结果看,传统后备保护本身隐藏的不安全因素、保护彼此之间以及保护与安全自动装置之间缺乏配合,是引起和扩大电网连锁跳闸事故的重要原因。广域测量系统和通信技术的发展为后备保护的改进提供了有力的技术支持。本文将广域信息引入到后备保护系统中,对传统后备保护的整定原则和结构功能进行了改进,在完成传统保护功能的同时,可以有效避免后备保护隐藏故障,实现与其他支路后备保护及安全自动装置之间的配合,防止大电网连锁跳闸事故的发生。论文主要完成了以下几个方面的工作:为满足后备保护控制的需要,在分析支路切除后其原有潮流的转移将对部分支路造成较大影响的基础上,提出了能反映潮流转移影响范围的线路相关集的概念及其搜索方法。电网中的支路切除会造成系统潮流的重新分布,但只有部分支路受潮流转移影响较大,有可能影响其后备保护的动作行为。本文用线路相关集的概念来表示这些支路。文中对线路相关集进行了数学描述与定义,分别介绍了基于决策树理论和基于改进最短路径算法两种方法来搜索线路相关集。线路相关集的确定为广域后备保护彼此之间进行信息交换及信息采集划定了范围。在线路相关集的基础上,定义了线路相关因子,介绍了并行路径法和矩阵法两种线路相关因子的计算方法。利用线路相关因子能够对支路开断引起的潮流转移进行定量的分析。通过对线路相关因子的计算,可以快速准确地预测出支路断开后转移潮流在其线路相关集中各支路上的分布,从而为后备保护控制策略提供可靠的数据支持。针对多支路连锁切除事件引起的潮流转移问题,研究了发生多支路切除事件时的线路相关集及线路相关因子的搜索方法和计算方法。通过数学推导得出多支路切除事件的线路相关集及线路相关因子计算公式,将线路相关集进一步从单支路切除推广到多条支路切除的情况,建立了完备的线路相关集理论体系。对近年来造成大停电事故的主要原因——后备保护的隐藏故障问题进行了详细的分析,在此基础上发展了系统脆弱态的概念。针对整定原因造成的后备保护隐藏故障,本文基于线路相关集理论,结合后备保护隐藏故障发生的机理,提出了在系统正常运行时对脆弱态的辨识方法和识别判据,为系统的安全校验提供了新的方法。针对传统后备保护整定原则的局限性,借助先进的通信手段,对当前广泛使用的距离Ⅲ段后备保护整定方法进行了改进,在根据系统运行方式进行调整的自适应整定原则的基础上,增加了过负荷保护的功能,并在识别本支路短路故障、相邻支路短路故障和过负荷状态的基础上提出了变时限的整定方法,可以有效避免后备保护隐藏故障的出现。对广域后备保护实时减载控制系统的总体结构、功能配置、流程设计等关键问题进行了研究,利用线路相关集理论提出了一种新的实时减载算法,包括最佳减出力点和减负荷点的选取原则以及最优减载量的计算方法,构建了广域后备保护的控制方案,可实现线路相关集内各支路后备保护彼此之间以及后备保护与安全自动装置之间的配合,可以有效预防大电网连锁跳闸事故的发生。更多还原

【Abstract】 With the construction of new pattern about "one EHV and three LARGE" for power system, the scale of power networks in China becomes larger and larger. The large-scale transmission networks improve the economy of power system; but at the same time the probability of great cascading failure is increased too. In recent years, many widely spread outages have been happened in many countries which reveal the defects in protection and stability and emergency control. By analyzing these outages, it could be known that the unwanted operation of backup protection which based on local information worsened the situation in the expanding of outages and accelerate the collapse of power system no matter what the reason and course of the outages. Therefore, the wide area information is introduced into the backup protection system in this dissertation in order not to protect the transmission line but also to realize the cooperation between the backup protection of other lines and the safety automatic device to prevent the power network from cascading failures. Major work can be summarized as follows.The definition and searching method of RCTL (relative cluster of transmission line) which can reflect the transferring direction of power flow is presented based on the fact that when the faulted line is cut, the transferring of original power flow will seriously affect some transmission lines. The cut of the branch line will lead to the redistribution of the flow of total power network. However, only several power flow of transmission lines are affected severely. In a certain operation mode, each transmission line possesses its fixed and close related transmission lines. So in the dissertation the mathematic description and definition of RCTL is processed, and two searching methods-decision tree theory based and shortest paths based-are also presented. For wide area backup protection, the collection of wide area information is limited. The definition of RCTL not only decides the range in choosing wide area information, but also establishes the base of realizing the load-shedding controlling strategy of backup protection.Based on the RCTL, line relative factor (RF) is defined and two calculating methods-parallel route method and matrix method-are also presented. Quantitative analysis of power flow transferring caused by tripped branch circuit can be processed by using line relative factor. By calculating the line relative factor, the power flow transferring distribution in each branch circuit within RCTL can be accurately forecast, which can provide the reliable data for load-shedding controlling strategy of backup protection.The searching method and calculating method of RCTL and line relative factor when multi-lines are cut off are presented to deal with the power flow transferring problem caused by cascading cut of multi-lines. The calculation formula of RCTL and line relative factor of cascading cut of multi-lines is obtained by mathematical derivations, which extends the RCTL from single line cutoff to multi-lines cutoff and establishes the complete theory system of RCTL.The concept of system frangibility mode of hidden failure is developed by detailed analysis of the hidden failure of backup protection-the main reason of wide spread blackouts in recent years. An evaluating method of hidden failure happening probability of backup protection is also presented based on the RCTL. To eliminate the hidden failure of backup protection caused by the protecting setting, the identification method and criterion system frangibility mode during the normal operation are presented based on the RCTL theory and the mechanism of hidden fault of backup protection.Against the setting principle limitation and defect of traditional backup protection and using the electrical information provided by data acquisition system and modern communication, the widely used distance stage III of backup protection is improved and the method of identifying short circuit and over-load status is also presented. Based on the above achievements, self-adaptability setting principle which can adjust itself according to the power operational mode and over-load protection function are enhanced in distance stage III protection. The setting method of varying time limit is presented on the basis of short circuit fault identification of this line and the neighboring line and the over-load status identification, which can lessen the occurring probability of setting hidden fault effectively.The real time load-shedding controlling strategy of backup protection is presented based on the wide area information, which can realize the corporation between the backup protections of each line and the corporation between backup protection and safety automation devices, which can effectively prevent the power network from cascading failures. The key problems of overall configuration, function allocation and process design of load-shedding controlling system of backup protection are studied. A new real time load-shedding algorithm is put forward and the realizing scheme of wide area backup protection is made up according to the change of load and power flow, which can prevent the power grid from cascading trip effectively.更多还原