Which overload protection device is the most sensitive for detecting small amounts of current leakage to the ground?

The Ground Fault Circuit Interrupter (GFCI) is designed specifically for detecting small amounts of current leakage to the ground, making it the most sensitive among the options provided. Unlike traditional fuses or circuit breakers, which are intended primarily for overcurrent protection that can happen during overload situations, a GFCI actively monitors the current flowing through a circuit. If it detects a discrepancy between the outgoing current and the returning current, it interprets this as a potential leakage of current to ground, which could pose a shock hazard to a person.

The GFCI can trip very quickly, often in less than a second, thereby reducing the risk of electrical shock. This sensitivity allows it to protect in scenarios where traditional protective devices might not react quickly enough to prevent dangerous situations.

Fuses, circuit breakers, and relays serve different functions and are not specifically designed for ground fault protection. Fuses react to excess current, while circuit breakers offer similar protection but can also reset after tripping. Relays, on the other hand, are used for controlling circuits rather than providing direct protection against current leakage. Thus, the GFCI is uniquely qualified for the role of leakage detection and personal safety in electrical systems.