在三相四线制低压配电网中，如果三相负载不对称，将会产生不平衡电流通过中性线流至系统侧，中性线能够消除中性点电位变化使各相电压保持对称，从而使中性线对地电位为零。然而中性线由于过流或其他故障断开时，必然会导致三相负载中性点偏移，可能造成用电设备烧毁或不能正常工作等状况。针对上述问题，从理论角度出发阐述了低压配电网中性线断线的危害，对比分析了各种中性线断线检测方法之后，在采用直流信号注入法的基础上设计了一种新型检测电路，利用多个单元检测装置实现断线位置的定位，分析此方法对基于电流互感器的漏电保护的影响，结果表明该方法能够同时满足断线检测和漏电保护的要求。通过仿真验证了上述方法的科学性与正确性。

In a three-phase four wire low-voltage distribution network, if the three-phase load is asymmetric, an unbalanced current will flow through the neutral line to the system side. The neutral line can eliminate the potential change at the neutral point and keep the voltage of each phase symmetrical, thereby making the potential of the neutral line to ground zero. However, when the neutral line is disconnected due to overcurrent or other faults, it will inevitably cause the neutral point of the three-phase load to shift, which may cause electrical equipment to burn out or malfunction. In response to the above issues, the harm of neutral wire breakage in low-voltage distribution networks was explained from a theoretical perspective. After comparing and analyzing various neutral wire breakage detection methods, a new detection circuit was designed based on the DC signal injection method. Multiple unit detection devices were used to locate the breakage position. The impact of this method on current transformer-based leakage protection was analyzed, and the results have showed that it could meet the requirements of both breakage detection and leakage protection simultaneously. The scientific and correctness of the above method have been verified through simulation.