What component is primarily responsible for monitoring current balance in an RCD?

The component primarily responsible for monitoring current balance in a Residual Current Device (RCD) is the sensor. The sensor functions by continuously comparing the current flowing through the live and neutral conductors. In a properly functioning circuit, the current entering through the live wire should equal the current returning through the neutral wire. If there is a discrepancy—indicating that some current may be leaking to ground due to a fault—the sensor detects this imbalance.

When an imbalance is detected that exceeds a predetermined threshold, the sensor signals the RCD to trip, effectively disconnecting the electrical supply. This rapid response helps to prevent electric shock and reduces the risk of electrical fires. Understanding the role of the sensor is essential for recognizing how RCDs enhance electrical safety by monitoring current flow and providing critical protection against faults.