小电阻接地系统间歇性接地故障的动态增量判据及保护方案

摘要

When the single phase intermittent earth fault occurs, it is instantaneous and the ground current is small, which make the fault difficult to be identified. This paper analyzes the reason that the traditional inverse-time overcurrent protection and even three-section current protection can not operate correctly and the possible severe consequences caused by the fault. This paper analyses the circuit caused by the fault by both simulation and record of the fault disturbance recorder. Then, a solution combined the“dynamic increment”criterion based on the characteristics of the circuit and the energy management system is presented to identify and clear the fault. The solution improves the reliability of the power system with neutral grounding via low resistance.%为准确识别小电阻接地系统间歇性接地故障，以该故障实际案例为例进行研究，分析了故障发生时传统反时限及三段保护无法正确动作的原因及该故障可能引发的严重后果。进一步对该故障进行仿真，结果表明间歇性单相接地故障的故障电流有效值不高且持续时间短，即具有冲击性及间歇性。针对该特点，提出一种相应的电流动态增量判据，并结合微机系统设计故障的保护方案逻辑流程，形成微机系统动态增量保护方法。该方法可对间歇性单相接地故障的准确识别进而进行保护，提高小电阻接地系统运行的可靠性。