What is the minimum feeder disconnect rating that triggers ground-fault protection on a solidly grounded, 150 V to ground wye system?

What is the minimum feeder disconnect rating that triggers ground-fault protection on a solidly grounded, 150 V to ground wye system?

• A. 1000 amperes.
• B. 500 amperes.
• C. 200 amperes.
• D. 2000 amperes.

Answer: (A)

Ground-fault protection of equipment is required for feeders when the system is solidly grounded and the feeder disconnect rating is at least 1000 amperes. On a solidly grounded 150 V to ground wye system, the NEC sets the trigger at 1000 A or more, so the minimum feeder rating that would require GFPE is 1000 amperes. If a feeder is rated at 2000 A, it would also require GFPE, but that’s not the minimum—1000 A is the threshold that starts the requirement.

Ground-fault protection of equipment is required for feeders when the system is solidly grounded and the feeder disconnect rating is at least 1000 amperes. On a solidly grounded 150 V to ground wye system, the NEC sets the trigger at 1000 A or more, so the minimum feeder rating that would require GFPE is 1000 amperes. If a feeder is rated at 2000 A, it would also require GFPE, but that’s not the minimum—1000 A is the threshold that starts the requirement.