【作者】 周志成；

【导师】 何俊佳；

【作者基本信息】 华中科技大学 ， 电气工程， 2007， 博士

【摘要】 小电流接地系统发生单相接地故障时,形成的过电压会加速电气设备绝缘老化,容易造成绝缘闪烙及事故扩大,因此,要求故障选线装置快速、准确地选择并切除故障线路。由于小电流接地系统的接地故障复杂多变,单个选线方法普遍存在选线盲区,工况适应性差,故障选线准确率低。本文结合小电流接地系统中性点接地方式特点,提出基于多源信息融合的模糊决策的故障选线判据实施单相接地故障选线,开发了故障选线装置样机并进行了试验。本文总结了当前小电流接地系统中性点三种运行方式的特点及其应用。分析了当前小电流接地系统的选线方法及其优缺点,针对造成小电流接地系统选线难的因素,如故障建模难、故障特征信号微弱、消弧线圈等其他继电保护装置的干扰等,指出选线装置应根据不同的中性点接地方式采用多源信息特征量进行故障选线。本文以系统发生单相接地故障时的相电压和接地电流的变化为对象,讨论了电力系统中性点接地方式的划分依据及其特征。利用对称分量法分析了三种中性点接地方式下的单相接地故障情况,给出了零序电压、零序电流等物理量的表达式,并简析了系统发生单相接地故障时,各种接地方式下线路中零序分量的分布规律,为故障选线判据的设计奠定理论基础。本文对与单相接地故障特征相似的PT一次断线、系统断相和铁磁谐振故障进行了深入分析,分别提出了比较PT的线电压大小辨别PT一次断线故障和比较各相电压大小及其变化辨别系统断相故障的有效判据;提出了改进插值FFT算法和Prony算法提取谐振信号的谐波特征,从而快速准确地辨别谐波谐振类型(分次谐波谐振或高次谐波谐振)及有效消谐。本文针对单判据选线正确率低的特点,根据故障信号特征量变化规律和信号强度分别建立各选线方法的故障测度隶属函数和权系数函数,利用模糊判断取代传统的逻辑判断。基于多源信息融合技术综合各选线方法的优势,建立了NUS、NES两种系统的模糊决策故障选线判据体系。同时,针对NES的固有缺陷,提出了提高选线装置准确率的有效措施,如增大故障残流、配合消弧线圈调档采集数据等。利用仿真软件EMTP-ATP对小电流接地系统中的多种接地故障情形进行了大量的仿真,验证了选线方法的有效性。本文根据理论分析建立的模糊决策故障选线判据,基于PC104总线,开发了DOS操作系统下的小电流接地选线装置,并且对选线装置进行了两次系统的试验。试验结果表明:在系统发生单相接地故障情况下选线装置具有极高的选线准确率和良好的适应性。更多还原

【Abstract】 When the single phase-to-earth fault occurs in the non-effectively grounded system (NUGS), the system can be permitted to operate for a period of time in order to enhance the reliability. However, the over-voltage will accelerate the insulation of equipment to become older, and arose the insulation flashover. Thus, the fault line must be selected and removed quickly and accurately by the fault line selection device. Because of the complexity of NUGS, there are some dead areas for the present fault line selection method, whose adaptability and robust are weak, and the correctness of fault line selection is low. Referring to the characteristics of grounded mode in the NUGS, the criterion of fuzzy decision-making fault line selection is prospered to carry out the fault line selection on the basis of multi-source data fusion, and a fault line selection device is developed and some tests are carried out.Firstly, in this paper the characteristics and application of three kinds of neutral operation mode are summarized. The fault line selection methods and their advantage and disadvantage in the NUGS are detailed. Aiming at the difficult factors of fault line selection, such as the difficult fault modeling, the faint fault signal, the unstable grounding arc and the interfere of arc-suppression or other relay protection, the fault line selection must be carried out by using the multi-source information characters according to the different neutral operation mode.when the single phase-to-earth faults occur, through analyzing the change of phase voltage and fault grounded current, the dividing criterions and characteristics of neutral grounded modes are explained. According to the symmetry weight method, the single phase-to-earth faults of three kinds of grounded modes are analyzed, and the expressions of zero sequence voltage and zero sequence current are detailed, and the distributing laws are indicated under all kinds of grounded modes, consequently, the theory is established for the criterion design of fault line selection in the paper.And then in this paper, the line break of PT’primary winding and the system’s phase break and the ferroresonance fault occur in the NUGS, the biggish zero sequence voltage will be exported from the PT’s open-delta, whose fault characteristic is similar to the single phase-to-earth fault, which are deeply researched in this paper. At the same time, the criterions of comparing the line voltage to distinguish the line break of PT’s primary winding fault and comparing the phase voltage and its change to distinguish the system’s phase break are prospered. And the improved interpolate FFT arithmetic and Prony arithmetic are prospered to obtain the harmonic characteristic quickly and accurately when the ferroresonance occurs, and then distinguish the types of harmonic resonance (frequency dividing resonance or higher frequency resonance), so that the ferroresonance eliminator can be effective.Aiming at the low veracity of present fault line selection method, some fault measurement membership functions and some criterion weight coefficient membership functions of fault line selection method are defined inspectively according to the variational law of fault signal character and the intension of fault signal, and the conventional logic judgment is replaced with the fuzzy judgment. Based on the large information fuse technology, the criterion of fuzzy fault line selection for the NUGS is built up under the neutral ungrounded system (NUS) and the neutral resonance system (NES). Especially, some good ways are prospered to enhance the veracity of fault line selection device for the inherent defectiveness of NES, such as increasing the remaining current, cooperating with the arc-suppression coil when carrying out data acquiring and so on. Aiming at many single phase-to-earth fault cases in the NUGS, many simulations are carried out by the EMTP-ATP software, and the fault line selection methods are validated.Finally, according to the criterion of fuzzy decision-making fault line selection built by the theory analysis above, the fault line selection device is developed under the DOS operate system on the basis of the PC104 bus, and some tests are carried out for the fault line selection device. The test results show that the fault line selection device has the high veracity of fault line selection and better application when the single phase-to-earth fault occurs in the NUGS.更多还原