2. Residual current device (RCD) protection against ground faults

2.1 Principle and different types of devices

Earth leakage protection consists of three parts (figure 12 ) which can be incorporated into the same device or separated:

• detection, consisting of a toroid which surrounds all the active conductors of the circuit to be protected; when the vector sum of the currents in the conductors is zero, no current flows in the toroid's secondary circuit; if a difference occurs, for example in the event of a downstream earth fault, a current will be induced in the secondary circuit;

• measuring the current detected by the toroid; when this current reaches a predetermined value,...