What is the full form of RCD?

The most common and widely accepted full form of RCD is Residual Current Device. An RCD is a safety device used in electrical wiring systems to quickly disconnect the circuit if it detects an imbalance between the live and neutral currents, which could indicate a ground fault or leakage of current—protecting people from electric shocks and helping prevent electrical fires.

Alternative meanings: While "Residual Current Device" is the standard interpretation in electrical safety, in a railway context, RCD can sometimes stand for "Railway Communication Display," a device used in control centers for monitoring and managing railway operations. However, this usage is niche compared to the predominant electrical safety application.

Key functions of an RCD:

• Personal safety: RCDs can prevent fatal electric shocks by detecting even small leakage currents (as low as 5–30 mA) and disconnecting the power within milliseconds (typically less than 30 ms).
• Fire prevention: By interrupting faulty circuits, RCDs help reduce the risk of electrical fires caused by faults in appliances or wiring.
• Distinction from other breakers: Unlike standard fuses or circuit breakers (MCB, MCCB), which protect against overcurrent or short circuits, RCDs specifically protect against residual (leakage) current, which may not trip a conventional breaker.