Hi z bus Ct configuration 1

[B4rancher]

I've encountered a bus Ct application that I need some help wrapping my head around. Two breakers with 2000:5 contributions to PVD's. Hi side transformer ct's DO Not contribute directly, are 1200:5 and are wired in parallel to the 1200:5 taps on the BKR ct's.
I see this is necessary to accommodate the mis-match of ratios and I see what appears to be an auto transformer affect making this work but I need to be in tune to what all is working together here before I remove one Bkr from service completely while maintaining my bus protection. I'm lacking sufficient Ct engineering theory to reconcile this. Any advise shall be greatly appreciated and thanks in advance.

 

[Marmite]

PVD's?

An AC schematic single line diagram would be a big help.

Regards
Marmite

 

[dpc]

Aux CTs not a good idea for High Z bus differential, if that is what you are talking about.

 

[jghrist]

Yes it is possible to use CTs of different ratios. See

SEL-587Z Relay Application With Multiratio Current Transformers
Application Guide - This application guide deals with incorporating mixed ratio current transformers in the protection scheme and obtaining a satisfactory operation of the relay with high security against external faults.

 

[vijaypandiyan]

SLD or scheme is preferred to support you better.

Thanks,
Vijay

 

[ProtectionEngineer]

Please see attached file.

 

[B4rancher]

Protectionengineer, Thanks, exactly what I needed and could not find myself on web.
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