利用零序电流倍增特征的不接地系统故障选线

针对中性点不接地系统单相接地故障选线困难的问题,通过母线故障相接地故障转移与中性点接入小电阻的方式来增强故障信息从而选出故障线路。建立了故障转移阶段、并联电阻投入前后各个阶段的零序网络模型,分析了健全线路和故障线路各自的零序电流幅值的变化特征。在中性点小电阻投入、母线开关分闸前后各馈线零序电流幅值变化明显,健全线路零序电流在母线开关分闸后显著减小而故障线路零序电流增大。利用故障线路与健全线路的零序电流变化特征构建了不接地系统故障选线判据。大量的仿真计算验证了该方法对于不接地系统单相接地故障良好的适应性,有助于进一步提高故障选线准确率。

Fault Line Selection Method of Non-earthing System by Using Zero-sequence Current Multiplication

In view of the difficulty of single-phase earthing fault line selection in the neutral non-earthing system,it is proposed in this paper to enhance the fault information by way of the earthing fault transfer of the faulty phase of bus and access to the small resistance of the neutral point so to select the faulty line.The zero-sequence network model of various stages is set up during the fault transfer stage and before and after switching the shunt resistor.The variation characteristics of respective zero-sequence current amplitude for sound and faulty lines are analyzed.The variation of zero-sequence current amplitude of each feeder is significant in the switching of small resistance of the neutral point and before and after opening the bus switch.The zero-sequence current of the sound line significantly decreases after the opening of the bus switch,while the zero-sequence current of the faulty line increases.A fault line selection criterion of non-earthing systems is constructed by using the zero-sequence current variation characteristics of the faulty and sound lines.The good adaptability of the method for single-phase earthing faults in non-earthing systems is verified by a large number of simulation calculation,which helps to improve the accuracy of fault line selection further.