System and method for detecting faults in an aircraft electrical power system

An aircraft electrical power system includes a monitored load (e.g. group of lightbulbs) connected through a sub_system power unit and a power distribution center to a power bus. A current monitor of the power distribution center is able to detect a total failure of the sub_system power unit and its connected monitored load, but is not able directly to detect the failure of a single load component (e.g. single lightbulb). The sub_system power unit includes a fault detector able to detect a fault or failure of a single load component (e.g. single lightbulb) in the monitored load. When the fault detector detects such a fault, the sub_system power unit generates a modulated current signal in the current drawn by the sub_system power unit, with a magnitude greater than the detection threshold of the power distribution center, which thus recognizes the detected fault based on the modulated current signal.