随着我国煤炭开采行业机械化与自动化程度的进一步提高，煤矿电网供电负荷明显上升，供电系统更加复杂，极易发生电气故障。统计表明，矿井电网中发生故障的类型以单相接地故障为主，约占电气故障总量的 。由于井下施工时的环境特殊，当某处发生单相接地事故时危害较大，可能损伤电气设备，甚至引发爆炸、火灾等事故。目前，对于煤矿井下发生单相接地故障选线的问题一直没有很好的解决方案，为此本文将对煤矿电网接地选线问题进行研究。

本文对煤矿电网中性点不接地及经消弧线圈接地系统在发生单相接地故障时的稳态和暂态过程的形成机理和特征进行了分析，从理论上探讨了馈线零序电压、零序电流的分布规律和相关特性。通过Matlab搭建煤矿井下电网的仿真模型，分别对零序功率方向法、五次谐波法及首半波法进行了仿真，并分析各方法的优缺点及应用范围。同时，本文详尽分析了零序导纳法的基本原理并对其进行了仿真和分析，在此基础上提出改进导纳法。改进导纳由基波导纳与五、七次谐波导纳构成，并将五个周波的改进导纳值进行累加相量求和，得到更加清晰的故障方向。仿真结果表明，改进导纳法能够有效减小零序导纳复平面上的误动区域。

本文使用ONLLY-A430继保仪模拟故障信号，设置零序电压与零序电流的不同相位差来模拟可能发生的故障情况并进行实验验证。实验数据表明，改进导纳法能够准确选出故障线。最后使用供电监控系统安全性能验证装置，设置矿井三级变电站不同位置发生接地，在不同测量点采集信号，验证改进导纳法的有效性。实验结果表明，改进导纳法适用于井下多级供电系统单相接地故障选线。

With the further betterment of the mechanization and automation of the coal mining industry in my country, the power supply load of the coal mine power grid has increased substantially, the power supply system is more complex, and electrical failures are more likely to occur. Statistics show that the type of fault may occur in the mine power grid is single-phase grounding fault Mainly, accounting for about 80% of the total electrical faults in the mine power grid. Due to the special environment during underground construction, when a single-phase grounding accident occurs somewhere, it is more harmful, which may damage electrical equipment, and even cause explosions, fires and other accidents. At present, there has been no worthy solving to the difficulty of single-phase grounding fault line selection in coal mines. For this reason, this article will discuss the problem of grounding line selection of coal mine power grids.

This paper analyzes the formation principle and features of the steady-state and transient processes of the neutral point ungrounded system and the single-phase grounding fault of the arc suppression coil grounding system in the coal mine power grid, and theoretically discusses the related characteristics of the zero sequence voltage and zero sequence voltage. The simulation model of the underground coal mine power grid was built by Matlab, and the zero sequence power direction method, the fifth harmonic method and the first half wave method were simulated, and the advantages and disadvantages of each method and the scope of application were analyzed. At the same time, this paper analyzes the basic principles of the zero-sequence admittance method in detail and simulates and analyzes it. On this basis, the improved admittance method is proposed. The improved admittance is composed of the fundamental waveguide and the fifth and seventh harmonic admittance. And the improved admittance values of five cycles are accumulated and phasor summed, and finally a clear fault direction is obtained. The simulation results show that the improved admittance method effectively reduces the misoperation area on the zero-sequence admittance complex plane.

This paper uses ONLLY-A430 relay protection instrument to simulate the fault signal, set the different phase difference between the zero sequence voltage and the zero sequence current to simulate possible fault conditions and conduct experimental verification. The experimental data shows that the improved admittance method can accurately select the fault line . Finally, the safety performance verification device of the power supply monitoring system is used to set the grounding at different locations of the mine three-level substation, and the signals are collected at different measurement points to verify the effectiveness of the improved admittance method. The experimental results show that the improved admittance method is suitable for single-phase ground fault line selection in underground multi-level power supply systems.

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