选择性Powerformer定子单相接地保护研究

发布时间：2018-03-21 04:25

本文选题：Powerformer　切入点：定子单相接地保护　出处：《长沙理工大学》2014年硕士论文　论文类型：学位论文

【摘要】：Powerformer是ABB公司研制的一种新型同步发电机,理论机端输出电压高达400kV,可省去升压变压器直接与电网并联,具有运行效率高、运行寿命长、环境效益好等优点,应用前景广阔。定子绕组单相接地故障是发生概率最高的发电机内部故障之一,是匝间故障及更严重的内部故障的先兆,加之Powerformer机组的运行特点,定子绕组单相接地故障及故障Powerformer的准确检测关乎Powerformer机组及电网的安全稳定运行。然而,现阶段国内外对选择性Powerformer定子单相接地保护研究相对较少,且现有保护方案存在灵敏性不高与可靠性不强等不足。因此,本文对选择性Powerformer定子单相接地保护展开了研究。本文主要包括五部分内容。第一部分首先概述了Powerformer的发展历程并对发电机中性点接地方式进行了探讨；随后概述了传统发电机定子单相接地保护的国内外研究现状,并指出了现有保护方案的不足；最后概述了选择性Powerformer定子单相接地保护的国内外研究现状。第二部分首先介绍了Powerformer的设计特点与运行特点；随后详细介绍了Powerformer的内部故障模型。第三部分首先分析了并列运行Powerformer机组内部发生定子单相接地故障或外部系统发生单相接地故障时Powerformer机组的零序电流等效网络,提出了Powerformer机端零序电流与泄漏电流的提取方案；随后,根据Powerformer内部故障仿真模型对机端零序电流与泄漏电流提取方案进行了仿真验证,仿真结果体现了理论分析的正确性与提取方案的有效性。第四部分基于信息融合思想提出了基于系统聚类的选择性Powerformer定子单相接地保护方案,该保护方案融合了四种故障信息,首先将训练样本投射到四维空间,在四维空间中应用系统聚类方法将训练样本分为故障类与非故障类,并求出故障聚类中心与非故障聚类中心；随后,通过比较待测样本在多维空间中到两个聚类中心的距离判别待测样本的类别,进而判别Powerformer的运行状态；最后,仿真验证了保护方案的有效性。第五部分提出了基于判别分析的选择性Powerforme r定子单相接地保护方案,保护方案首先提取四种判别因子,对训练样本进行学习,构造判别模型；随后,将待测样本代入判别模型,根据判别准则判定待测样本的类别,判定Powerformer的运行状态；最后,仿真验证了保护方案的有效性,并通过与其余保护方案的对比体现了该保护方案的优越性。仿真结果表明,论文提出的基于系统聚类与基于判别分析的保护方案均能有效完成选择性Powerformer定子单相接地保护,并且不受系统运行方式的影响,体现了本文所提出的保护方案的有效性；不同保护方案保护性能的对比体现了本文提出的保护方案具有更高的可靠性与灵敏性。
[Abstract]:Powerformer is a new type of synchronous generator developed by ABB Company. The output voltage of the theoretical machine is up to 400kV, which can save the direct parallel connection between the booster transformer and the power network. It has the advantages of high operation efficiency, long service life and good environmental benefit. The single-phase grounding fault of stator winding is one of the most probable internal faults of generator, which is the precursor of inter-turn fault and more serious internal fault, as well as the operation characteristics of Powerformer unit. The accurate detection of stator winding single-phase grounding fault and fault Powerformer is related to the safe and stable operation of Powerformer unit and power grid. However, at present, there is relatively little research on selective Powerformer stator single-phase grounding protection at home and abroad. And the existing protection schemes have some shortcomings, such as low sensitivity and low reliability. In this paper, the selective Powerformer stator single-phase grounding protection is studied. This paper mainly includes five parts. In the first part, the development of Powerformer is summarized and the neutral grounding mode of generator is discussed. Secondly, the research status of single-phase earthing protection of generator stator is summarized, and the deficiency of the existing protection scheme is pointed out. At last, the research status of selective Powerformer stator single-phase earthing protection is summarized. The second part introduces the design and operation characteristics of Powerformer. Then the internal fault model of Powerformer is introduced in detail. In the third part, the zero-sequence current equivalent network of Powerformer unit is analyzed when the stator single-phase grounding fault occurs in parallel operation Powerformer unit or the single-phase grounding fault occurs in external system. A scheme for extracting zero sequence current and leakage current at the end of Powerformer is proposed, and the scheme of extracting zero sequence current and leakage current at the end of Powerformer is simulated according to the Powerformer internal fault simulation model. The simulation results show the correctness of the theoretical analysis and the validity of the extraction scheme. 4th, based on the idea of information fusion, a selective Powerformer stator single-phase grounding protection scheme based on system clustering is proposed, which integrates four kinds of fault information. Firstly, the training samples are projected into four dimensional space, and the training samples are divided into fault and non-fault classes by using the system clustering method in the four-dimensional space, and the fault clustering centers and non-fault clustering centers are obtained. By comparing the distance between the tested samples and the two clustering centers in multidimensional space, the categories of the samples to be tested are determined, and the running state of the Powerformer is judged. The simulation results show the effectiveness of the protection scheme. In part 5th, a selective Powerforme r stator single-phase grounding protection scheme based on discriminant analysis is proposed. Firstly, four discriminant factors are extracted from the protection scheme, and the training samples are studied and a discriminant model is constructed. Then, the test samples are substituted into the discriminant model, and the classification of the samples to be tested is determined according to the discriminant criterion. Finally, the validity of the protection scheme is verified by simulation. The simulation results show that the proposed protection scheme based on system clustering and discriminant analysis can effectively accomplish the selective Powerformer stator single-phase grounding protection. And it is not affected by the operation mode of the system, which reflects the effectiveness of the protection scheme proposed in this paper, and the comparison of the protection performance of different protection schemes shows that the protection scheme proposed in this paper has higher reliability and sensitivity.
【学位授予单位】：长沙理工大学
【学位级别】：硕士
【学位授予年份】：2014
【分类号】：TM31

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