Unbalanced 3 Phase Transformer Clarification

If the neutral is grounded at the source, then the voltage at this place with respect to earth will be 0V. Any voltages w.r.t. earth elsewhere on the neutral are the result of currents flowing through the resistance of the neutral conductor, and simply an expression of unbalanced or mixed single-phase loads applied to the system.

I can certainly understand unbalanced loads, but how do you get a 3 phase transformer with different impedance windings? Is this a home-made kluge made from three single-phase transformers, or perhaps a standard 3 phase transformer with one or more partially shorted windings? In either case, the transformer should be replaced!

The only other possibility I can think of would be where the three phases are not all connected to the same transformer tap number, perhaps trying to compensate for an unbalance on one phase.

What did you use to measure the transformer impedance? did you test/measure the voltage from its actual output, at the end of the cable attached to it, or did you calculate it?

let me rephrase, if you have a transformer supplying various single phase loads between each phase and it's neutral point, and the number of loads between phase A and neutral is different to phase B and neutral, then you have unbalanced loads on the transformer.

My understanding is, with an ungrounded neutral point, there will be a voltage present on the neutral point of the transformer, as the vector sum of voltages for all 3 phases is no longer zero at the neutral point.

When you ground the neutral point, what happens to this voltage which results on the neutral point as a result of unbalanced loading on the transformer?

OK, now this sounds like a number of 120V single phase loads connected to the different phases of a 208V 3-phase transformer. If the neutral point is not grounded, then you can't guarantee 120V between any phase and neutral. The more heavily loaded phase will drop in voltage, and the other phases will rise. This could easily lead to destruction of some devices on the lightly loaded phase(s).

Yes I understand that, since the neutral point is floating, the voltage difference between phases and neutral is no longer the same. There is a voltage present on the neutral.

What happens to this voltage when the neutral is grounded? Does the voltage appearing at the neutral point, as a result of the unbalanced phases flow to ground?