CT for Motor differential Protection

[HamidEle]

Wonder if there is any particular requirement for the CT on motor differential protection, such as CT accuracy class. To me, there should not be any difference with other overcurrent protections as the CT may see the same external faults as well. Any inputs would be greatly appreciated.

 

[ScottyUK]

What type of differential scheme are you talking about?

 

[HamidEle]

A large induction motor.

 

[ScottyUK]

I was thinking more in terms of high impedance or low impedance. The former is quite demanding on the CTs.