Delta/Wye Transformer Secondary GF Detection
Delta/Wye Transformer Secondary GF Detection
(OP)
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.
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.






RE: Delta/Wye Transformer Secondary GF Detection
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.