A bit of a debate among'st my peers about utilizing paralleling generators with dissimilar vector group transformers.
The theory goes as such: Generator A will be energizing the LV side of a Yd11 4160:600Vac transformer. Generator B will be energizing the LV side of a Yd1 4160:600Vac transformer. Both transformers have identical impedance % values. Both generators have sync scopes that match gen voltage to the bus voltage on 600Vac LV side before closing their respective breakers.
The common point of connection is on the HV side.
Generator A closes to dead-bus first energizing both transformer A and subsequently transformer B in a rather series orientation. Phase shift from LV to HV of transformer A will lead by 30 degrees which will energize Transformer B and subsequently be leading again by another 30 to the LV side. Generator B will now see a reference voltage 60 degrees leading of Generator A but it should not care: it'll sync to that voltage and close to the live bus.
The debate now is: will circulating-current (or cross-current) still be an issue, many of my peers say it will but refuse to explain and I cannot see how; as the difference in potential has now been neutralized by phase-shifting Generator B to match. thoughts?
Edited to eliminate vagueness: Both generators are identical in pitch windings (.6667 or 2/3rds), both have methods of KVAR sharing and both excitation systems are externally-powered PMG type and are tuned identically to produce exactly 600Vac L-L. Simply: is the vector group dissimilarity enough to produce circulating-current?