中性点经消弧线圈的接地方式是配电网的一种运行方式，当线路发生单相接地故障时，其故障电流小而增加了故障检测的难度。所以小电流接地系统发生单相接地故障的选线问题一直是电力系统继电保护的重要研究课题和难题。 为了进一步明确单相接地故障特征，建立中性点经消弧线圈接地电网单相接地故障时的瞬时序网络模型，其可同时描述单相接地故障的暂态过程和稳态过程，丰富了故障选线的基础理论；通过计算给出瞬时正序电流实部的数学表达式，分析表明故障支路瞬时正序电流实部的幅值大于非故障支路的瞬时正序电流实部，相位超前于非故障支路的瞬时正序电流实部，此特征可作为选线判据。 根据故障瞬时正序实部特征量的特征，建立了基于瞬时正序电流实部比幅比相的选线方法，采用FFT滤波提取瞬时正序电流实部基波，比较故障支路和非故障支路的瞬时正序电流实部的幅值和相位来准确选择故障线路，利用MATLAB建立仿真模型验证选线方案的可行性和准确性。 提出将基于瞬时正序电流实部比幅比相选线算法应用在智能变电站的几个方案，充分发挥了智能变电站一次设备智能化和二次设备网络化的特点，有利用变电站选线技术水平的提高。

One of the main grounding modes in distribution network is neutral point via arc suppression coil grounding, it helps to improve the reliability of power supply, but the difficulty of fault detection is increased due to its small fault current. In neutral point via arc suppression coil grounding system, the problem of single phase grounding fault line selection is an important research topic in power system protection, and its also is a tough problem. In order to investigate the unclear process characteristics for single-phase grounding fault occurring, a neutral through petersen coil grounding grid when single-phase earth-fault of instantaneous sequence network model is established. It can also describe the single-phase earth fault transient process and steady state process and enrich the basic theory of fault line selection. By analyzing sequence current instantaneous which are given by the mathematic expression of the real part, it can be seen that the instantaneous real and imaginary part of the positive sequence current amplitude and phase have very big difference, the characteristic as the research provides a theoretical basis for single-phase earth fault line selection. According to instantaneous positive sequence fault characteristics, real characteristics of the transient is established based on the sequence current real component ratio and the phase ratio of line selection method, using FFT filtering to extract the instantaneous real fundamental positive sequence current, comparative fault branch and the branch of the instantaneous real component of positive sequence current amplitude and phase to accurately select fault line, the model simulated by MATLAB is used to verify the feasibility and accuracy of line selection scheme. Based on instantaneous real than picture than positive sequence current phase line selection algorithm, several scheme of intelligent substation is selected; giving full play to the intelligent substation a intelligent equipment and secondary equipment networked characteristics, it is good for the rise of the technical level of the transformer substation line selection.