A current consumed by an electric consumer is sampled as a first sampled current, and a main current sensor samples a current provided by an electric supply system as a second sampled current. A fault current detector detects a fault current between the electric supply system and the electric consumer, based on a non-zero difference between the first sampled current and the second sampled current and, in response, generates a circuit break signal. A residual current device receives the circuit break signal and, in response, to breaks a circuit between electric supply system and the electric consumer.