Which device primarily protects against ground faults in electrical circuits?

The device that primarily protects against ground faults in electrical circuits is the ground fault circuit interrupter (GFCI). A GFCI is designed to detect imbalances in the electric current between the hot and neutral wires, indicating a potential ground fault, such as when current is leaking to the ground. When it senses this imbalance, the GFCI quickly shuts off the electrical circuit to prevent electric shock, thereby protecting individuals from serious injury.

This type of protection is crucial in wet or damp environments where the risk of ground faults is higher, such as kitchens, bathrooms, and outdoor locations. GFCIs are specifically mandated in electrical codes for these areas because they provide a safety measure that regular circuit breakers or fuses do not offer.

While fuses and circuit breakers serve to protect against overloads and short circuits, they do not specifically address ground fault conditions. A transformer, on the other hand, is used for changing voltage levels in AC systems and does not provide protection against electrical faults. Therefore, the GFCI's unique function in monitoring and responding to ground faults makes it the correct answer.