小电流接地故障选线定位问题在现场一直没有得到彻底解决。不少情况下，仍用传统的顺序拉闸法和目测巡线法查找故障线路和故障点。经过多年的研究，已有多种不同的选线原理问世，并有多种实用化装置投入运行，取得了一定的应用效果。但是，由于各种查找单相接地故障的保护装置主要利用了较小的特征量作为判据，准确率较低。为基于单相接地故障稳态量的典型选线定位原理，利用零序电流、零序电压的幅值和相位关系构成判据，判据特征量较小。为基于单相接地故障暂态量的选线定位原理，虽然故障的暂态量比稳态量大很多倍，但有故障电气量存在时间短不易采集故障数据的缺陷。为基于外加诊断信号的选线定位原理，该类原理开辟了小电流接地故障选线定位原理的新蹊径，以“S注入法”为代表，因从母线PT 的二次侧向故障相注入特殊的交流信号，受母线 PT 容量的限制，注入的判据信号较微弱。为利用信息融合理论的综合性选线定位判据，尽管各种选线原理一定程度上能够取长补短，但每一种选线原理仍然是依据较小的判据特征量，特别是高过渡电阻故障时，判据特征量更小，不能从本质上提高选线定位的准确率。
The problem of fault line selection and location for small current grounding has not been thoroughly solved in the field. In many cases, traditional sequential brake pulling method and visual inspection method are still used to find fault lines and fault points. After years of research, a variety of different line selection principles have been published, and a variety of practical devices have been put into operation, and achieved certain application results. However, due to the use of small feature values as criteria, the accuracy of various single-phase grounding fault detection devices is low. In order to locate the typical fault line based on the steady state of single-phase grounding fault, the criterion is made up of the magnitude and phase relationship of zero-sequence current and zero-sequence voltage, and the criterion features are small. In order to locate the fault line based on the transient value of single-phase grounding fault, although the transient value of the fault is many times larger than that of the steady dakeluo.89ix.comdiaosu.71ix.comjinggaiz.89ix.comwusuanna.89ix.com jinggaif.89ix.comliuliangji.37ix.com.cnstate, there is a shortcoming that the fault electrical quantity has a short time and is not easy to collect fault data. In order to locate the fault line based on the principle of additional diagnostic signal, this kind of principle opens up a new way of locating the fault line of small current grounding. It is represented by "S injection method". Because special AC signal is injected into the secondary fault phase of bus PT, the criterion signal injected is weak due to the limitation of bus PT capacity. In order to make use of the comprehensive criteria of line selection and location based on information fusion theory, although various principles of line selection can complement each other to a certain extent, each principle of line selection still relies on smaller criterion characteristics, especially in the case of high transition resistance faults, the criterion features are smaller and the accuracy of line selection and location cannot be improved essentially.