小电阻接地系统接地故障反时限零序过电流保护

Zero-sequence Inverse-time Overcurrent Protection in Low Resistance Grounding System with Grounding Fault

现有的小电阻接地系统接地保护主要采用定时限零序过电流保护,定值较高,高阻接地时容易拒动。结合反时限过电流保护的特点,在分析小电阻接地配电网单相接地故障零序电流分布特征的基础上,提出一种改进的反时限零序过电流保护方法。通过各条出线保护间的横向配合,可使保护的启动电流定值无须躲过本线路的最大对地电容电流,显著降低了其启动门槛值,提高了高阻接地故障保护能力。通过MATLAB仿真验证了提出的反时限零序过电流保护的速动性和可靠性。

The existing grounding protection for low resistance grounding system mainly adopts zero-sequence definite-time overcurrent protection,whose setting value is too high to act when high impedance grounding fault occurs.Considering the characteristics of inverse-time overcurrent protection,based on the analysis of the fault current distribution characteristics of single-phase grounding fault in low resistance grounding distribution network,an improved zero-sequence inverse-time overcurrent protection method is proposed.The starting current setting value of the protection doesn’t need to escape from the maximum capacitance current of the outlet,with the crosswise coordination among each outlet,so that the starting threshold is greatly reduced,which can effectively improve the protection ability of the high impedance grounding fault.The speed and reliability of the proposed zero-sequence inverse-time overcurrent protection are verified by MATLAB simulations.