What is the function of a Residual Current Device (RCD)?

What is the function of a Residual Current Device (RCD)?

• A. It detects imbalance between live and neutral currents and trips
• B. It increases circuit breaking capacity
• C. It measures voltage drop
• D. It stores energy for later use

Answer: (A)

RCDs protect people by detecting earth leakage. They continuously monitor the current going through the live conductor and the return current in the neutral conductor. When both currents are equal, no net current leaves the circuit. If some current leaks to earth—through a person or through faulty insulation—the currents become unbalanced. The RCD senses this residual current and trips the switch quickly to disconnect the circuit, reducing the risk of electric shock. This device does not increase the circuit’s breaking capacity, nor does it measure voltage drop, nor store energy for later use. Those functions belong to other protective devices or systems. Typically, RCDs trigger on small leakage levels (around 30 mA in many domestic applications) to provide fast protection.

RCDs protect people by detecting earth leakage. They continuously monitor the current going through the live conductor and the return current in the neutral conductor. When both currents are equal, no net current leaves the circuit. If some current leaks to earth—through a person or through faulty insulation—the currents become unbalanced. The RCD senses this residual current and trips the switch quickly to disconnect the circuit, reducing the risk of electric shock.

This device does not increase the circuit’s breaking capacity, nor does it measure voltage drop, nor store energy for later use. Those functions belong to other protective devices or systems. Typically, RCDs trigger on small leakage levels (around 30 mA in many domestic applications) to provide fast protection.