Exciting Current of CTs - Differential / REF

[charz]

The attached article says that the relay setting should be above the sum of the exciting currents in the parallel CTs. ( I got this article from one of the old threads on this same forum).

Does it mean the exciting currents of the CTs circulates through the relay path?
how does the exciting current of the current transformer affect the sensitivity of the relay?

 

[stevenal]

So the excitation current just happens to add up linearly in the operating coil like an in-zone fault? And without explanation? To properly show excitation current, one needs to show the excitation branch of the CT equivalent circuit. I'm unimpressed with the article.

 

[KSS227]

The sensitivity majorly affected in bus bar protection where the no. of CT's are more. If the actual values of Imag are not considered, the relay tends to operate on the inappropriate fault current than the setting current due to multiplying factor of Imag currents of all CT's.