Ground fault circuit interrupter (GFCI) is an electrical protection device which disconnects the power if a current leakage to ground is detected. There are two types of GFCIs which are named as life protection GFCIs and equipment protection GFCIs.
Life Protection GFCI:
This GFCI is used to prevent the shock hazards to the personal particularly in bathrooms and around water. Without a GFCI, a person who touches a hot wire while standing in water or on wet floor will get shocked because his or her body provides an electrical path to the hot wire current to flow to the ground. The GFCI opens/trips the circuit breaker quickly if it senses that more current in the hot wire than in neutral wire, indicating that the current has found an alternate path to ground. (Through the persons body).
The power lines from the power source are equipped with the circuit breaker. After the circuit breaker, GFCI is connected between the hot and neutral wire in the form of toroidal coil. If any imbalance (High current flows) with hot wire, the solid state sensing circuit senses and commands the circuit breaker to open.
Equipment Protection GFCI:
This GFCI is used to prevent equipment damage and possibly fire due to internal arching. Under normal circumstances, a current should not flow in the safety wire of the equipment. For example the motor current should flow in hot and neutral wires not in the ground wire. Only if there is a short circuit or fault between the hot wire and motor chassis will there be a small current in the ground wire. This fault current may not be sufficient to trip the overload or earth fault detector but it can cause a fire hazard in the equipment. The GFCI monitors the excess current in hot wire and opens a circuit breaker id the current exceeds a preset level.
Apart from the above two types GFCIs in physical divided as GFCI outlet, GFCI circuit breaker, portable GFCI. They perform the same function of protection but the application is different.
It is a replacement of standard electrical outlet which provides protection for the appliances plugged in to it. It has hot wire slot and neutral wire slot and one small hole. It checks the imbalance in current flow and acts for even Milli ampere difference.
GFCI Circuit Breaker:
These acts as replacement of standard circuit breakers in home main switch board. It provides the protection of the entire circuit, it is economical to place the GFCI circuit breaker instead of putting GFCI outlet in all bath rooms and kitchens. Once it is tripped due to fault it has to be reset by fully switching off it and switching on again to restore the power.
Portable GFCI are used generally contract workers at work sites. These does not need a ground to function. These are generally used the places where you have to bring power from unprotected outlets.