保定零序电流互感器电气厂

中性点不接地和消弧线圈接地系统用零序电流互感器变比的选择。

Neutral point grounding and arc suppression coil grounding system with zero sequence current transformer is variable than choice. 

这种系统接地电流较大时，或保护最小启动电流较小时，可选用大一些变比的零序电流互感器，如50/1；100/1；100/5；150/5及以上。可是有的中性点不接地系统一般不允许接地电流超过10A，所以一般10A以下保护就要动作。消弧线圈接地系统由于电感电流和电容电流的中和后，一般也不会有超过10A的接地电流（一般都是过补偿，实际接地电流已是电感电流）由于使用的综合保护（不用综合保护的有时用高灵敏度零序电流互感器，和与其配套的继电器，见2）。就要求有整定值，一般定值≤10A，如整定值一次电流为5A，可考虑100/5A或20/1A ，一次电流5A时，二次电流0.25A，一般已超过综合保护的启动电流。如综合保护最小启动电流>0.25A也只好选用75/5；50/5；15/1；10/1的变比，这些变比的零序电流互感器最好选用整体式的，否则精度要差一些。

This system when the grounding current is larger, or protect the minimum starting current is small, can choose a few bigger than zero sequence current transformer, such as 50/1. 100/1; 100/5; 150/5 or more. But some of the neutral point grounding system generally do not allow the grounding current of more than 10 a, 10 a commonly so the following protection will be action. Arc suppression coil grounded system due to the inductance and capacitance current after neutralization, generally there will be no more than 10 a grounding current (typically compensation, the actual grounding current is inductance current) due to the use of comprehensive protection (without comprehensive protection sometimes with high sensitivity of zero sequence current transformer, and the matched relay, see 2). Would require setting value, fixed value 10 A or less commonly, such as setting the value of A current of 5 A, may be considered A 100/5 or 100/5. A, A current of 5 A, the secondary current is 0.25 A, generally has more than protecting the starting current. Such as protecting the minimum starting current > 0.25 A, also had to choose 75/5. 50/5; 15/1; 10/1 of strain ratio, the strain ratio of zero sequence current transformer had better choose integral, otherwise is less precision.