Wye Secondary, Floating Neutral, Missing SBJ

[infinity]

Does anyone have a laymen's explanation as to why a Wye transformer that is missing the SBJ would have strange voltage readings to ground?

 

[don_resqcapt19]

It is an ungrounded system without the system bonding jumper. The voltages to ground are based on the capacitance of the phases to ground.
If the capacitance on each would be identical, you would see the same voltage as line to XO, but that would be unusual and you see "strange" voltages.

 

[LarryFine]

Does anyone have a laymen's explanation as to why a Wye transformer that is missing the SBJ would have strange voltage readings to ground?

Another explanation: With no conductor solidly connected to ground, there is no set voltage to ground from any other conductor. Your trying to read voltages between points that are not connected to each other. Your meter is enough to shift voltages while measuring.

Picture a simple doorbell transformer:

Ground either secondary wire, and you'd have one wire that measures 16v to ground and one wire that measures 0v to ground.

Don't connect either secondary to ground, and your meter could read almost anything (or nothing) from either wire to ground.

 

[kwired]

Another explanation: With no conductor solidly connected to ground, there is no set voltage to ground from any other conductor. Your trying to read voltages between points that are not connected to each other. Your meter is enough to shift voltages while measuring.

Picture a simple doorbell transformer:

Ground either secondary wire, and you'd have one wire that measures 16v to ground and one wire that measures 0v to ground.

Don't connect either secondary to ground, and your meter could read almost anything (or nothing) from either wire to ground.

And the capacitance Don mentioned is the reason why.