3 phase delta voltage to ground 2

[ggood]

Quick Question- What would I read on a volt meter if I measured one leg to any building ground on an ungounded 3 phase delta 480 volt secondary??

 

[jghrist]

Somewhere between zero and 277 volts, depending on the capacitance to ground of the connected cables and equipment and on the input impedance of the meter. Maybe more if the capacitance to ground is not balanced.

 

[tinfoil]

If the delta system happens to have an earth fault, you will see ~480V on two legs, and ~0 on the earthed leg.

 

[tinfoil]

By the way, make sure that your voltmeter has a decently high imput impedance (such as no less than 10 MegaOhms) and that your leads are fused, as you do not want your meter to become the 'second path to ground' on the delta system.