Delta/Wye Transformer Secondary GF Detection

[7carisfast]

13.8V/480V Delta/Wye 2000 KVA VPI Dry transformer. Customer would like to add secondary GF detection.
Right or wrong, I'm thinking of a large zero-sequence CT installation.
Questions:
Normally, one would set a zero-seq relay at very low settings to detect leakage. If there is a Phase-Ground fault internal to the transformer (i.e. upstream of the CT), would the CT see an unbalanced load since say 'B' phase was removed. Or wouldn't the CT relay even detect a fault? Or is the secondary CT only able to detect a fault downstream of the CTs.

 

[alehman]

Normally the CT in this type of application wouldn't be used for low level leakage detection. Typically ground overcurrent pickup would be set between 200 and 1000 amps.

The CT should be downstream of the neutral-ground bond. In that case it can only detect faults downstream. The CT should include the neutral conductor, so an open phase or unbalanced load will not be detected as a fault.