Judging by the different magnitude and direction of the wavelet packet coefficient modular maximum , we can select the single phase - to - earth line . the method using wavelet singularity detection theory to extract the fault time is discussed . a fault distance measurement algorithm combining wavelet analysis used for separating the character from the transient fault signal with artificial neural networks used for the nonlinear approximation from the transient character to fault distance is presented 论文提出利用各个出线零序电流在频带上小波包系数模极大值的方向和大小的不同来实现故障选线，讨论了利用小波分析的奇异性来判断故障启动时刻，提出将小波分析和人工神经网络结合，利用人工神经网络的非线性逼近能力，实现故障暂态量到故障距离的非线性映射，完成测距。
The main work of the first part includes : analyzing the theory of measuring direction and distance of the target by three elements symmetrical and dissymmetrical array , comparing the measuring error of two kinds of array , discussing the characteristics of time delay in passive distance measurement , giving valid method of time delay estimation , and discussing the restriction of this method and the distance wrapping in passive ranging 对三元非对称阵被动测距技术的主要研究工作包括：分析了三元对称阵和非对称阵测向测距的原理，对两种阵型的测向、测距误差进行了对比分析，探讨了三元阵被动测距中时延差的特点，提出了有效的时延差估计方法，并对该方法的局限性以及被动测距中存在的距离模糊问题进行了探讨研究。
This system can be applied to many fields ( mini near - distance radar , aircraft radar ) as long as the front antenna and transceiver systems are well organized . it can be applied to vehicle radars for distance measurement . this paper is consisited of 6 chapters : chapter i : the basic theory of lfmcw radar ; chapter ii : key features and development basics of the dsp used in the system ; chpter iii : the algorithm and analysis of lfmcw signal processing ; chapter iv : the hardware architecture and software design ; chapter v : dsp peripheral interface used in the system ; chapter vi : the performance test , the comparison with the former system and the conclusion 本论文一共分为6章:第一章论述了线性调频连续波( lfmcw )雷达的基本原理;第二章说明本处理系统中使用的核心dsp的性能以及dsp开发的基本方法;第三章说明了本处理系统采用的核心算法;第四章详细介绍了系统的硬件结构以及基于这种硬件结构的软件设计;第五章对系统中dsp应用的最重要的外设部分进行了详细的说明;第六章介绍了对本信号处理系统的性能测试;并对本系统以及与前一系统的设计做了相应的比较,并指出了改进的地方与好处。
The dissertation first generally introduces the present researching and application situation of the domestic and international three fault distance measurement methods which exit now . they are transmission line impedance method and the fault analysis method and the traveling wave method . then , the fault characteristics of the small current grounding system are explained 本文首先概括地介绍了国内外现有输电线路阻抗法、故障分析法及行波法三种故障测距算法的研究及应用现状，说明了小电流接地系统的故障特点。
The principle of the fault distance measurement for small current grounding system by injecting dual frequency signal are discussed from many aspects such as the method and the characteristic of the signal , the test of the signal , the method of the line select , the algorithm of the fault distance measurement , and the method of the fault location , etc . the task adopts this kind of principle , in which the signal injection is completed by the coupling between the power source and the pt 在详细地说明以上三种测距算法的基本原理后，分析各种算法的优缺点，从注入信号的方法、特征，注入信号的检测，接地选线的方法，故障测距的算法，及故障定位的方法等多个方面，论述了本课题采用的应用于小电流接地系统的双频信号注入式测距原理。其中，信号的注入由功率源通过电压互感器( pt )耦合来完成。
