NCEES #126 Power

[threatta]

So, I want to double check myself here. The reason that you can't parallel a wye-wye and a wye-delta transformer is because the secondary voltages would be 30 degrees out of phase. That is due to the wye-delta transformer shifting the phase 30 degrees while the wye-wye doesn't, correct? You can parallel like transformers (i.e. 2 wye-deltas, 2 delta-wyes, 2 delta-deltas or 2 wye-wyes)?

 

[Flyer_PE]

^Correct.

 

[MSEE_PE]

So, I want to double check myself here. The reason that you can't parallel a wye-wye and a wye-delta transformer is because the secondary voltages would be 30 degrees out of phase. That is due to the wye-delta transformer shifting the phase 30 degrees while the wye-wye doesn't, correct? You can parallel like transformers (i.e. 2 wye-deltas, 2 delta-wyes, 2 delta-deltas or 2 wye-wyes)?

The main problem with connecting 2 transformers with the same rating but different configuration the phase shift which can cause circulating currents.

 

[kris7o2]

Is this for NCEES 125. The question for NCEES 126 asks about a grounded industrial power system and what would be least likely to improve