Ground-fault protection is required for a feeder disconnect if any of the following conditions apply.

• A. The feeder is rated 1,000 amps or more
• B. It is a solidly grounded wye system
• C. The system voltage is 480Y/277 volts
• D. All of these

Answer: (D)

Ground-fault protection of equipment is required on feeders to quickly detect and interrupt a ground fault, protecting equipment and reducing shock and fire hazards. This protection is needed for large feeders because the potential fault energy is significant, so a fast disconnect minimizes damage. A solidly grounded wye system has a direct path to ground, making ground faults more consequential unless promptly cleared, so GFP is appropriate. Higher system voltages, like 480Y/277 V, carry more fault energy and risk, reinforcing the need for protection. Since any one of these conditions triggers the requirement, the correct choice is all of these.