Differential Protection CTs from different Vendors

[NickParker]

What are the possible issues to be taken care of while purchasing the CTs from different vendors?
The application is for Motor Differential Protection for a MV Motor. The HV Switchgear side CTs are by the switchgear Vendor and the Motor Neutral side CTs by the Motor Vendor.

Any heads up!

 

[cuky2000]

I do not foreeseen any problem using CTs from different manufacturers as long the selected rating is adequated for the application.

 

[Hoxton123]

When i worked in a motors and generator factory we did this many times. We had a sister company on site who made HV switchgear, and made their own CTs.

If the switchgear was 'ours' we got the matching CTs.

Otherwise we got the CT data from the customer and got the CT division to make make matching CTs.

Rarely had a problem, worst one was fitting large CTs into a relatively small motor terminal box.

 

[RRaghunath]

The practice is client does the CT sizing calculation and tells the motor and switchgear vendors the requirement.
The other approach is to include CT sizing calculation in the scope of relay vendor and pass the information to the other vendor(s) as appropriate.
If the relays are part of switchgear, then it is switchgear vendor and if the relays are part of Motor control/relay panel then motor vendor.
If the motor differential is biased type, the CT requirements are less stringent. But, in case of high impedance differential, the CT parameters need to be closely matched and hence more attention needs to be paid.