【作者】 谢宏丽；

【导师】 林军；

【作者基本信息】 福州大学 ， 电力系统及其自动化， 2004， 硕士

【摘要】 单相接地故障在小电流接地系统中出现的比较频繁，此时必须尽快找到故障线路，以避免两相对地短路。本文首先分析了小电流接地系统发生单相接地故障时的情况，指出选线所遇到的主要困难，进而对小电流接地系统单相接地故障的选线及测距的方法做了比较和综述。接着对小电流接地系统单相接地故障时零序电流的暂态过程及特点做了介绍和分析。鉴于实验室已有的小电流接地系统选线硬件的研制只通过了实验室里的动模试验，故选用Matlab软件对小电流接地系统进行大量的单相接地故障仿真试验，仿真的采样率和硬件基本一致，由于硬件中带有低通滤波器，故在进行采样数据的Morlet小波分析时先采用db15小波对采样进行一维离散小波的多尺度分解，使得分解得到的低频信号刚好包括了小电流接地系统单相接地故障时的暂态高频信息，然后对这一信息再继续进行小波算法分析，分析结论表明利用变换后的实部、虚部和模值能够较准确的实现单相接地故障时的故障选线和暂态高频分量的提取。从而更进一步验证了硬件的可行性。更多还原

【Abstract】 The single phase-to-grounding fault frequently occurs in neutral ungrounded system. The fault line must be found to avoid a phase-to-phase fault .In this paper, firstly, the condition on single phase-to-grounding fault occurring in neutral ungrounded system are discussed and then the main troubles in choosing fault line are pointed out. Further, the methods are proposed to compare and summarize for choosing fault line and detecting distance in neutral ungrounded system. Subsequently, the characteristics of zero sequence current and transient courses are introduced and analyzed. Since that the choosing line hardware for the neutral ungrounded system has just passed part of the dynamic simulative test, MATLAB software was chosen to do a lot of simulative tests on single phase-to-grounding fault. And the simulative sampling ratio is almost the same as the hardware’s. Because there is a low wave filter in the hardware, I choose the db15 wave-let to carry out the multidimensional decomposition on the sample by the method of one dimension discrete wavelet in order to obtain low frequency signal including the high frequency transient information on single phase-to -grounding fault. Then I analyze the information continuously by wave algorithm. Plenty of experiments show that the fault line can be accurately chosen and the high frequency of transient signals can be precisely identified with the real part , imaginary part and module of wavelet transform. Therefore it proves the feasibility of the hardware.更多还原