能量法小电流接地方向判据的应用研究

为解决小电流接地系统中利用单点电气量难以准确判断接地故障方向的问题，提出了一种改进的能量法接地方向判据。根据叠加原理分析了单相接地故障暂态等值电路，指出了测量点处的零序能量由故障初始时刻的电容充电能量和维持LC振荡的稳态振荡能量两部分组成，分析了零序能量在不同接地方式和不同接地电阻下的特点。为了简化定值整定原则，对零序能量函数进行了离散化处理并作了二次积分，提出了实用的能量二次积分判据。对中性点不接地方式、中性点经消弧线圈完全补偿的接地方式下的金属性故障和经3000 ?电阻接地故障进行了仿真测试。仿真结果表明，上述各种故障情况下该判据均能判别故障方向。

Application of the criterion of small current grounding direction of the energy method

It is difficult to accurately determine the ground fault direction using a single-point electrical quantity in a small current grounding system. Thus an improved energy method-based grounding direction criterion is proposed. From the superposition principle, a single-phase ground fault transient equivalent circuit is analyzed, and the zero-sequence energy at the measurement point is composed of the capacitor charging energy at the initial moment of the fault and the steady-state oscillation energy to maintain the LC oscillation. The characteristics of the zero-sequence energy in different grounding modes and resistances are analyzed. To simplify the setting principle, the zero-sequence energy function is discretized and quadratic integration and a practical quadratic integral criterion is proposed. Simulation tests for a metallic fault and a 3000 ? resistance grounding fault are conducted on the neutral point ungrounded or the neutral point fully compensated ground via the arc suppression coil. Results show that the criterion can distinguish the fault direction in the above fault conditions. This work is supported by the National Key Research and Development Program of China (No. 2017YFB0903100).