基于接地故障比的不平衡配电网单相接地故障选相方法

为了解决传统故障选相方法可能因配电网不平衡度高或者高故障接地电阻而失效的问题，提出了一种基于接地故障比的不平衡配电网单相接地故障选相方法。首先建立了发生A相单相接地故障后接地故障比幅值和相位的解析表达式，通过将两个表达式对接地电导进行求导，并进行不同参数下的单调性分析，最终确定了发生A相SLG故障时零序电压幅值和相位的变化规律。然后将两种变化规律进行了整合，提出基于幅值和相位综合变化规律的故障选相方法。此外，还将A相的变化规律推广到B、C两相，并分析了欠补偿、过补偿和全补偿接地条件对所提方法的影响。最后通过Matlab仿真验证了零序电压变化规律和所提故障选相方法的有效性。仿真结果表明：在阻尼率为5%、三相不对称度为4.5%的4种工况下，传统故障选相方法均会失效，而所提方法能够保证故障选相的正确性。

Phase selection method of single line to ground fault in unbalanced distribution network based on ground fault ratio

In order to solve the problem that traditional fault phase selection methods may fail due to high unbalance or high fault ground resistance in distribution network, this paper proposes a phase selection method of single line to ground (SLG) fault in unbalanced distribution network based on ground fault ratio. First, the mathematical expressions of ground fault ratio amplitude and phase after a SLG fault occurs are established. By deriving the two expressions to the ground conductance and analyzing the monotonicity under different parameters, the variation law of zero sequence voltage amplitude and phase under SLG faults of phase A is finally determined. Then the two change laws are integrated, and a fault phase selection method based on the comprehensive variation law of amplitude and phase is proposed. In addition, the variation law of phase A is extended to phase B and C, and the effects of under compensation, over compensation and full compensation grounding conditions on the proposed method are analyzed. Finally, the variation law of zero sequence voltage and the effectiveness of the proposed fault phase selection method are verified by Matlab simulation. The simulation results show that under the four working conditions with damping rate of 5% and three-phase asymmetry of 4.5%, the traditional fault phase selection method will fail, and the proposed method can ensure the correctness of fault phase selection. This work is supported by the Key Project of Smart Grid Techniques and Equipment of National Key Research and Development Program of China (No. 2016YFB0900604).