电力变压器继电保护的研究

发布时间：2018-04-16 12:30

本文选题：电力变压器 + 差动保护　；参考：《青岛科技大学》2016年硕士论文

【摘要】：随着社会科学技术的飞快进步,人类文明的不断发展,电力工业也步入以特高压、高智能化为特点的新阶段,用户对供电系统的可靠性、稳定性、安全性等方面的要求越来越高。大型电力变压器作为为电力系统不可缺少、无法替代的重要电气设备,如果发生故障后不能得到迅速正确地处理,将会给整个系统带来严重的危害,因此电力变压器的继电保护工作十分重要。本文针对电力变压器的差动保护与后备保护,展开了深入研究。首先,对电力变压器差动保护原理与各种后备保护原理进行深入学习,并在SIMULINK平台上分别搭建了具有双侧电源的双绕组变压器系统仿真模型与具有多路出线的三绕组变压器系统仿真模型。通过分析仿真结果,验证两个模型能够正确的模拟仿真变压器空载合闸产生励磁涌流,以及变压器主保护区内外发生的各种电气量故障,为研究提供了仿真平台。针对传统差动保护涌流制动方法的局限性,在深入学习小波变换的基础上,本文选择用db4小波函数对励磁涌流与故障电流进行5层小波分解处理,观察分析各种情况下的励磁涌流与各种故障下的故障电流的小波变换特点。通过分析二者各层系数变化情况,本文提出一种基于小波系数分布为判据的励磁涌流识别新方法。该方法通过对小波变换后所得二尺度上的小波系数进行提取,计算其方差的变化情况,并设定合理的判据,来对励磁涌流与故障电流进行区分。通过仿真结果验证,本方法能够快速准确地区分励磁涌流与故障电流,并与传统方法比较,克服了传统方法的不足,具有很大的优势,有效地防止差动保护误动,具有应用前景。另一方面,针对变压器后备保护中过电流保护灵敏度不足以及各侧保护配合复杂等问题,提出以故障正序分量相位差为判据的变压器后备保护。利用数字化保护对线路信息采集量的冗余,提取故障分量,将变压器各侧线路与该侧各出线线路上的电流故障分量的正序分量进行相位的分析比较。通过所搭建的变压器模型的仿真验证,说明运用该方法能够正确地判断故障所在位置,解决变压器后备保护配合复杂,灵敏度低等问题,保证后备保护能够在故障出现且主保护拒动时,及时正确切除故障,保证变压器安全稳定运行。
[Abstract]:With the rapid progress of social science and technology and the continuous development of human civilization, the electric power industry has entered a new stage characterized by ultra-high voltage and high intelligence.Safety and other aspects of the requirements are higher and higher.As an indispensable and irreplaceable important electrical equipment for power system, large power transformer will bring serious harm to the whole system if it can not be dealt with quickly and correctly after failure.So the relay protection of power transformer is very important.In this paper, the differential protection and backup protection of power transformer are studied.First of all, the principle of power transformer differential protection and various backup protection principles are studied in depth.The simulation model of double-winding transformer system with double-side power supply and three-winding transformer system with multi-output line are built on SIMULINK platform.By analyzing the simulation results, it is verified that the two models can correctly simulate the excitation inrush current caused by the no-load switch of transformer and the various electrical faults occurring inside and outside the main protection area of the transformer, which provides a simulation platform for the research.In view of the limitation of traditional differential protection inrush current braking method, on the basis of deeply studying wavelet transform, this paper chooses to use db4 wavelet function to decompose excitation inrush current and fault current by wavelet decomposition.The characteristics of wavelet transform of excitation inrush current and fault current under various conditions are observed and analyzed.A new method of inrush current identification based on wavelet coefficient distribution is proposed by analyzing the variation of the coefficients of the two layers.By extracting the wavelet coefficients from the two scales obtained by wavelet transform, the variance of the coefficients is calculated, and reasonable criteria are set to distinguish the inrush current from the fault current.The simulation results show that this method can distinguish inrush current from fault current quickly and accurately, and compared with the traditional method, it overcomes the shortcomings of the traditional method, has great advantages, and effectively prevents the maloperation of differential protection.It has the prospect of application.On the other hand, in view of the insufficient sensitivity of over-current protection and the complex coordination of side protection in transformer backup protection, a transformer backup protection based on the phase difference of positive sequence component of fault is proposed.In this paper, the redundancy of line information collection is used to extract the fault component, and the phase analysis and comparison of the positive sequence component of the current fault component on each side of the transformer line and the output line of the transformer are carried out.Through the simulation and verification of the transformer model, it is proved that the method can correctly judge the location of the fault and solve the problems of complex coordination and low sensitivity of the transformer backup protection.When the fault occurs and the main protection fails, the backup protection can remove the fault correctly in time and ensure the safe and stable operation of the transformer.
【学位授予单位】：青岛科技大学
【学位级别】：硕士
【学位授予年份】：2016
【分类号】：TM41

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