零序电流保护的基本原理是基于基尔霍夫电流定律：流入电路中任一节点的复电流的代数和等于零。在线路与电气设备正常的情况下，各相电流的矢量和等于零，因此，零序电流互感器的二次侧绕组无信号输出，执行元件不动作。当发生接地故障时的各相电流的矢量和不为零，故障电流使零序电流互感器的环形铁芯中产 生磁通，零序电流互感器的二次侧感应电压使执行元件动作，带动脱扣装置，切换供电网络，达到接地故障保护的目的。 The basic principle of zero sequence current protection is based on kirchhoff's current law: the algebraic sum of the complex current flowing into any node in the circuit is zero. In line with the normal operation of electrical equipment, the vector of each phase current and zero, therefore, the zero sequence current transformer secondary winding no signal output, actuators is not action. When earthing fault occurring in the vector of each phase current and is not zero, the fault current of the zero sequence current transformer toroidal core middle magnetic flux, zero sequence current transformer secondary side of the induced voltage causes a actuators, drives the tripping device, switching power supply network, achieve the goal of earth fault protection.