由于输电线路距离长、穿越地域的地理因素复杂、气候多变,因此故障常发生于输电线路，并且故障点难以查寻。一旦发生故障，将对人民生活、经济发展带来巨大损失，那么对故障点快速、准确的定位是确保电力系统安全稳定运行的关键。 电缆、架空线波速度不统一、波阻抗不连续是困扰电缆-架空线混合输电线路故障测距的关键。本文采用基于时间变量的故障点搜索算法进行故障区段的判别，该方法以故障初始行波传播时间为参考量，通过联立时间关系方程组求解故障初始行波到达线路两端所需时间，从而判断故障点所在区段，在故障区段内采用传统的行波法进行故障测距，该方法能够避免混合输电线路波速度不一致的问题。 电流信号可以直接通过电流互感器进行提取，无需加装其他设备，方法简单，同时具有较高经济性。考虑到网络参数的依频特性，通过曲线拟合的方法进行对比发现，正序阻抗的依频特性变化缓慢。因此，本文选取暂态电流信号作为检测量，通过Karrenbauer变换，采用线模分量进行故障行波波头的提取。 小波变换对暂态故障信号具有良好的时-频分析能力，通过对时-频窗特性、消失矩、紧支撑性等方面的考察，选取三次B样条小波对故障信号进行分解，同时，三次B样条小波能够在抑制噪声方面和信号奇异性检测方面做出平衡。 利用ATP-draw程序搭建不同结构的混合输电线路模型，对仿真结果在Matlab程序下进行小波变换处理，仿真结果表明本文所采用的电缆-架空线混合输电线路测距方法准确可行。

Being the frequent fault area, transmission lines which have long distance always cross mountains. When fault occurred in transmission lines, it is hard to locate the fault area. It is important to protect transmission lines, in order to ensure power system safety and steadily. Nowadays, with the hybrid transmission lines which composed by high voltage cables and overhead lines have been widely used, an increasing number of researchers pay close attention to fault location for hybrid transmission lines. But inconsistent traveling velocity and no-matching impedance exists in hybrid transmission lines caused hard to distinguish the traveling wave. For these problems, the fault location algorithm based on variable of time has been used in this thesis. Compared current transformer to voltage transformer, it can be found that current transformer has wildly cut-off frequency band, which can be used in transient signal extraction. After frequency dependence of impedance analysis, it has been shown clearly that positive sequence impedance change more slowly than zero sequence impedance; therefore, line model component with stable parameters can be adopted as measurement signal. Wavelet transform has ability to analyze the fault transient information in time-frequency domain. Cubic b-spline has been used in fault signal decomposition which can make balance between signal de-noising and singularity detection. Through the ATP-draw simulation and data processing by Matlab, several simulations have been done, and the results show that the algorithm is accurate and feasible.