零序电流互感器作用原理
Principle of action of zero sequence current transformer
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，(http://www.dgzj.com/ 电工之家)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。
The zero sequence current protection is generally suitable for use in the TN grounding system. Because when there is a ground, the Id loop impedance TN-S system including phase impedance Z1, PE line impedance ZPE and contact impedance Zf, Zs=Z1+ZPE+Zf; Id for TN-C system, including the phase loop impedance impedance Z1, PEN line impedance ZPEN and contact resistance Zf, ZS=Z1+ZPEN+Zf; Id for TN-C-S system, including phase loop impedance PEN line impedance impedance Z1, ZPEN, ZPE and PE line impedance contact resistance Zf, namely ZS=Z1+ZPEN+ZPE+Zf, ground fault current generated by the Id=220/ZS phase, (http://www.dgzj.com/ electrical home) was significantly greater than when no fault three-phase unbalanced current, as long as the appropriate setting, it can detect the occurrence of zero sequence current grounding fault. To cut off the fault circuit. The IT system is generally used for the power supply reliability, higher requirements of single-phase grounding unnecessary immediately cut off the power supply circuit, but need to send the monitoring signal, in order to maintain the insulation failure to supply power for a period of time in the industrial and mining enterprises deserve a three-phase neutral line three line distribution line.