Reasons for Backfeed on Open Wye-Open Delta Banks

[power82]

Under what cirumstances can an open wye-open delta bank backfeed? I can see how it could happen if load is connected, but not without load.

 

[busbar]

Can you please elaborate? Backfeed from what?

 

[power82]

Let's say you've got a grounded wye system with two UG loops feeding two single phase transformers for a lift station. The transformers are connected open delta on the secondary. One of the loops is de-energized. Can this loop be re-energized from backfeed from the adjacent transformer?

 

[jbartos]

Suggestion: If "one of the loops" is properly de-energized, i.e. isolated from the other by opening switches or circuit breakers along the loop and on the open delta secondary, then there should not be any backfeed since all related interrupters (assuming that they are properly incorporated) are open.