Which device provides earth leakage protection?

• A. RCD
• B. MCB
• C. Fuse
• D. Surge protector

Answer: (A)

Earth leakage protection is provided by a residual current device. It continuously compares the current flowing in the live conductor with the current returning through the neutral conductor. Under normal conditions these two currents are equal, but if some current leaks to earth (for example, through a fault or a damaged appliance), there is an imbalance. The residual current device detects this imbalance and disconnects the circuit quickly to reduce the risk of electric shock.

This is different from overcurrent protection devices like a circuit breaker or a fuse, which respond to excessive current but do not monitor leakage to earth. A surge protector, meanwhile, guards against voltage spikes rather than detecting leakage. Some installations use an RCBO, which combines residual current protection with overcurrent protection, but the earth leakage protection role is still performed by the residual current function.