Quote Originally Posted by weressl View Post
OK, that makes sense. Do you have an explanation why both L/N and L/L voltages are listed when the transformer is clearly inteded to be connected to the L/N in other word to a single voltage? Isn't it clear that one of the connection - the one w/o the HV bushing - is the 'grounded' conductor? Or is it to assure and clarify that it is NOT to be connected to an ungrounded system?
It shows that it can be connected with 7200V_L-L from a delta system or 7200V_L-N from a wye system voltage across the winding. The standard would be to show this label as "7200/12470Y" (my transformer guide references ANSI C57.12.00).

Not sure why a straight "7200" label would not be sufficient unless the grounded system adds voltage stress or something. My guide just shows "7200" for a connection to a delta system and does not mention the wye system. It was not in my guide, but I remember reading about voltage stresses between the windings and the tank/neutral or something but I don't recall the exact details and would have to look it up to get it straight. If you are interested, I've got a reference in my office somewhere and could look for it.

If the poster has the correct voltage order, I suspect the poster left off the "Grd" part of the label which would indicate that it has reduced insulation at the neutral end and must be a grounded neutral. If the "Grd" voltage is on the left, it means the neutral end may be connected to the tank and would be labeled as "12470GrdY/7200".

Without the neutral connection to the tank allowed, it would be on the right as "7200/12470GrdY" but still indicating that the neutral must be grounded because of reduced insulation.