A power control apparatus comprises a transducer having an output (12,13) which is connected to a remotely activated device (25) mounted in a mains consumer unit (14). When a predefined parameter is detected, the device (25) is activated to connect a load (29) between the switched live output (18) of a residual current device RCD (15) and the neutral input (17) thereof, thereby creating an imbalanced current flow on the live and neutral output terminals (18,19) of the RCD (15) which causes contacts (20,21) inside the RCD (15) to disconnect the supply to an appliance circuit (22).