零序电流保护一般适合使用于TN接地系统。因为当发生一相接地时，对TN-S系统Id回路阻抗包括相线阻抗Z1，PE线阻抗ZPE和接触阻抗Zf，即Zs=Z1+ZPE+Zf；对于TN-C系统，Id回路阻抗包括相线阻抗Z1，PEN线阻抗ZPEN和接触电阻Zf，即ZS=Z1+ZPEN+Zf；对于TN-C-S系统，Id回路阻抗包括相线阻抗Z1，PEN线阻抗ZPEN，PE线阻抗ZPE和接触电阻Zf，即ZS=Z1+ZPEN+ZPE+Zf，产生的单相接地故障电流Id=220/ZS，明显大于无故障时的三相不平衡电流，只要整定合适，就可检测出发生接地故障时的零序电流，以切断故障回路。而对IT系统，一般均是使用对供电可靠性要求较高、对单相接地不必要立即切断供电回路、但需发出绝缘破坏监察信号、以维持继续供电一段时间的工矿企业内的不配出中性线的三相三线配电线路。
Zero sequence current protection is generally suitable for TN grounding system. Because when a phase is connected, the Id circuit impedance of the TN-S system includes the phase line impedance Z1, the PE line impedance ZPE and the contact impedance Zf, that is, Zs=Z1+ZPE+Zf. For TN-C systems, the Id loop impedance includes the phase impedance Z1, the PEN line impedance ZPEN and contact resistance. Z1, PEN line impedance ZPEN, PE line impedance ZPE and contact resistance Zf, that is, single phase grounding fault current Id=220/ZS produced by ZS=Z1+ZPEN+ZPE+Zf, is obviously larger than the three-phase unbalanced current without fault. As long as the setting is appropriate, the zero sequence current of grounding fault can be detected and the fault circuit can be cut off. For IT system, the three phase three line wiring road, which is not matched with the neutral line in the industrial and mining enterprises, is usually used for the high demand for the power supply reliability and the unneed of the single-phase grounding unnecessary to cut off the power supply loop immediately, but the insulation damage monitoring signal is needed to maintain the continuous supply of power supply for a period of time.