A power distribution system for connection to an AC voltage network, having a UPS power supply unit for uninterruptible power supply with a network-side input and with at least one output to which a number of loads are connected or can be connected in parallel load circuits, wherein a protective device having an electromechanical tripping device, in particular a thermal/magnetic tripping device, and having an evaluation and tripping unit is connected in the or each load circuit, which tripping unit trips the tripping device on the basis of an electronic overload and/or short-circuit characteristic curve and on the basis of the output voltage from the UPS power supply unit.