What Is a Residual Current Device (RCD)?
A Residual Current Device (RCD)—also known as a Ground Fault Circuit Interrupter (GFCI) in the U.S.—is a safety device designed to prevent electric shocks and reduce fire risks caused by electrical leaks.
Unlike standard circuit breakers, which protect against short circuits and overloads, RCDs monitor leakage currents that indicate a potential shock hazard or faulty insulation.
How Does an RCD Work?
An RCD constantly compares the current flowing through the live (hot) wire and the neutral wire.
✔ If both currents are equal, the circuit operates normally.
❌ If there’s an imbalance, it means electricity is leaking (possibly through a person or faulty wiring), and the RCD instantly shuts off power—usually within 30 milliseconds.