DETD fuses in the feeder are used to provide what function?

• A. Voltage regulation
• B. Overcurrent protection at maximum permitted rating
• C. Short-circuit current limiting
• D. Ground fault protection

Answer: (B)

DETD stands for dual-element time-delay fuses. In a feeder, their job is to provide overcurrent protection up to the feeder’s maximum continuous current rating. They’re sized to interrupt if the current exceeds what the feeder can safely carry, preventing overheating of conductors and insulation. The time-delay element lets through brief surges (like motor inrush) without nuisance blows, but will still open if the overcurrent condition persists. They don’t regulate voltage, and ground-fault protection is handled by other devices (GFCIs/RCDs), not these fuses.