融合小电流接地的矿山电网接地选线设计

煤矿井下低压电网运行环境特殊性及复杂性，导致利用单相接地故障零序电流进行选线的速度与准确度均有很大影响。为此，在深入研究小电流接地系统单相接地故障特点的基础上，提出将两个小电流接地系统相融合进行选线的思路，即正常运行于中性点不接地系统，当发生单相接地故障时，使系统运行在中性点高电阻接地状态进行故障选线，完成选线后，再恢复到原来中性点不接地状态运行。并给出了一个具体的将两个小电流接地系统相融合实用电路。该方法在大概率故障线路零序电流为最大的前提下，利用显著增大的故障与非故障线路特征量之间的差别，有效提升选线的准确度，可以明显提高保护动作的灵敏性。

Fault Line Selection of Coalmine Distribution Network Integrated Small Current Neutral Grounding System

Abstract: Because of the particularity and complexity of the operating environment of the low-voltage power grid in coal mine, the speed and accuracy of fault line selection by using the zero-sequence current of single-phase grounding are greatly affected. Therefore, on the basis of in-depth study of the characteristics of single-phase grounding in Small Current Neutral Grounding System, this paper puts forward the idea of combining two Small Current Neutral Grounding System for fault line selection, that is, normal operation of Isolated Neutral System when single-phase grounding, the system will operate in state of Neutral Point Grounding via High-resistance for fault line selection, after completing the fault line selection, it will return to the original state of Isolated Neutral System. A practical circuit integrating two Small Current Neutral Grounding System is given. Under the premise that the zero-sequence current of high-probability fault line is the maximum, this method can effectively improve the accuracy of fault line selection and the sensitivity of protective action by utilizing the difference between the fault and non-fault line feature which is significantly increased.