带零线电流判据的零线断线检测新方法

A New Method for Zero Line Disconnection Detection with Zero Sequence Current Criterion

当三相低压供电系统零线断线时,用户侧的中性点位移电压将发生偏移,可能烧毁大量用户设备。利用负载电压或中性点位移电压识别零线断线的方法在输电线路较长以及三相负载不平衡度较大时会误检。为了解决上述问题,理论分析了三相配电系统正常运行和零线断线时中性点位移电压、零线电流和负载不平衡度的特征关系。基于零线断线时中性点出现位移电压但没有零线电流的特征,提出了带零线电流闭锁判据的识别零线断线新方法,提高了零线断线检测的准确率,实例计算结果说明了方法的有效性。

When zero line disconnection occurs in three-phase distribution system, the displacement voltage will appear at the neutral point of the client, which may burn the equipments in a large area. The application of load voltage or the neutral point voltage to the detection of zero line disconnection may cause real-detection when the transmission line is long and three-phase load is unbalanced. In order to solve this problem, this paper studies the realationship among neutral point voltage, zero sequence current and load unbalance in normal conditions and when zero line disconnection occurs in three-phase distribution system. The theoretical analysis shows that： zero sequence voltage appears at the neutral point and there is no zero sequence current when the zero line disconnection occurs. Considering this characteristic, a new method to detect zero line disconnection is proposed based on zero sequence voltage with zero line current blocking. It can improve the accuracy of the zero line disconnection detection. And an example has proved the validity of the method.