GFCI (Ground fault circuit interrupter) according to Wikipedia is a device that shuts off an electric power circuit when it detects that current is flowing along an unintended path, such as through water or a person. It is used to reduce the risk of electric shock, which can cause the heart to stop or cause burns. Ground fault circuit interrupter is also called Residual Current Device (RCD).
Electric shock has been identified as the greatest risk involved with electrical equipment use. Severe electric shock can lead to burns, electrocution and death. The role of the GFCI is the reduce the risk of this electric shock, thereby protecting individuals.
GFCI’s are usually required by local laws to be installed in 2 prong receptacles, kitchens, bathrooms, unfinished basements, garages, outdoors, and anywhere near water.
How GCFI works
GFCI is a fast-acting circuit breaker designed to shut off electric power in the event of a ground-fault within as little as 1/40 of a second. With the exception of small amounts of leakage, the current returning to the power supply in a typical 2-wire circuit will be equal to the current leaving the power supply. If the difference between the current leaving and returning through the current transformer of the GFCI exceeds 5mA, the solid-state circuitry opens the switching contacts and de-energizes the circuit.
GFCI installation and testing
Installation must be done by a competent person and adequately tested before it is certified to be okay. To test your GFCI system, press the test button of the protection device to ensure it turns off the power to the connected load. This should be done whenever GFCI installation is done, before relying on it to protect you. Do not assume that the protection device is operational unless you have properly test it.
Types of GFCI
The Receptacle Type incorporates a GFCI device within one or more receptacle outlets. Such devices are becoming popular because of their low cost.
Portable Type GFCIs come in several styles, all designed for easy transport. Some are designed to plug into existing non-GFCI outlets, or connect with a cord and plug arrangement. The portable type also incorporates a no-voltage release device that will disconnect power to the outlets if any supply conductor is open. Units approved for outdoor use will be in enclosures suitable for the environment. If exposed to rain, they must be listed as waterproof.
The Cord-Connected Type of GFCI is an attachment plug incorporating the GFCI module. It protects the cord and any equipment attached to the cord. The attachment plug has a non-standard appearance with test and reset buttons. Like the portable type, it incorporates a no-voltage release device that will disconnect power to the load if any supply conductor is open.
GFCI is a protective device, but it can only protect when it has been properly installed and tested.
Hence, it is needful to install it according to the statutory requirements to ensure safety on individuals where necessary.
Also see watch how it works and how to test it here