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Thursday, January 23, 2020
Question:
Thank you for providing this service!
I have an ungrounded three-phase 480-volt delta system and was wondering what the phase-to-ground voltage is. Hopefully you can provide some clarification. Not sure if the NEC addresses this situation.
Kenneth McQuaid
A
Answer:
Hi Kenneth,
Ungrounded systems are dealt with in multiple NEC requirements. As for the voltage to ground for an ungrounded system, that information is specifically addressed in the definition of the term "voltage to ground." This definition indicates that Voltage to Ground. For grounded circuits, the voltage between the given conductor and that point or conductor of the circuit that is grounded; for ungrounded circuits, the greatest voltage between the given conductor and any other conductor of the circuit. So for an ungrounded 240-volt system the voltage to ground should be 240 volts. For an ungrounded 480-volt delta system, the voltage to ground would be 480.