基于暂态电流的小电流接地故障分界方法

Transient Current Based Demarcation Method of Small Current Grounding Fault

分析了谐振接地系统中用户系统内发生接地故障时,采用稳态零序过电流保护的分界开关拒动的原因。推导出了接地故障暂态零序(模)电流的表达式,分析界内与界外故障时分界开关测量到的暂态零序电流的变化特点,给出了暂态电流最大值与正常运行时稳态电容电流幅值的倍数关系。提出了基于暂态零序电流的接地故障分界方法及其整定原则,分析了暂态分界法的动作特性以及在界内故障时克服消弧线圈影响的效果。在电力系统实时数字仿真(RTDS)系统上进行模拟测试,验证了暂态分界法能够在界内故障时减少消弧线圈的影响、提高正确动作率。

This paper analyzes the causes of demarcation switch mal-operation of steady-state zero-sequence current protections, under the circumstance that a single-phase grounding fault occurs in the user systems of a resonant grounding system.An expression of transient zero-sequence current during the grounding fault is derived.This paper demonstrates changing characteristics of transient zero-sequence current perceived by the demarcation switch during internal/external faults.The multiple relationship between the maximal transient current value and the amplitude of the steady-state capacitor current in normal operation is given.This paper proposes a transient zero-sequence current based grounding fault demarcating method and the setting principle,and analyzes the operation characteristics of the transient demarcating method and its effectiveness of impairing the arc suppression coil impacts on the occurrence of an internal fault.The real-time digital simulation (RTDS)test results prove that the transient demarcation method can reduce the impact of arc suppression coil and improve the correct operation rate on the occurrence of internal faults.