What is the tripping mechanism of a GFCI designed to detect?

The tripping mechanism of a Ground Fault Circuit Interrupter (GFCI) is designed to detect when current leakage exceeds 5 mA. This threshold is critical for safety in preventing electrocution. The GFCI continuously monitors the electrical current flowing through the circuit; it compares the amount of current flowing to the electrical device and the amount returning from it. If there is a difference, which indicates that some current is leaking to the ground — potentially through a person who has come into contact with the device — the GFCI will automatically cut off the power to prevent serious electrical shock.

This sensitivity to currents as low as 5 mA is essential in environments like healthcare, where patients may be at heightened risk due to the presence of medical devices and the potential for accidental contact with water or bodily fluids. By tripping at this level, the GFCI provides a crucial safety mechanism to protect individuals from serious injuries or fatalities related to electrical hazards.