Differential protection device which makes it possible to detect a leakage or fault current in an electrical apparatus which is supplied with power either by at least two phase conductors (2, 2', 2", N) of a network or by at least one phase conductor (2, 2', 2") of a network and by a neutral conductor of said network, said device comprising at least one detection and control module which is functionally active or operational for frequencies of the fault signal from 0 Hz to a few tens of Hz, this module being supplied with power by the network, this module comprising, on the one hand, a measurement torus made of a ferromagnetic material which the aforementioned conductors (2, 2', 2", N) pass through, on the other hand, an excitation circuit for exciting the torus which comprises an AC signal generator which produces a periodic carrier and, finally, a measurement winding which is able and intended to generate a fault signal which results from the appearance of a differential fault in the network, said measurement winding being connected to circuits (7, 8, 9, 10) for processing and evaluating the fault signal and for transmitting a control signal for a breaking or opening means, which also forms part of the differential protection device, the aforementioned circuits (7 to 10) being arranged to form an operational electronic chain which belongs to the detection and control module, which device is characterized in that said operational chain of said module comprises a low-pass or band-pass filtering circuit, which forms the first circuit of said chain and processes the fault signal, or a derived signal (SD') which is directly dependent thereon, in order to extract therefrom the signal component which substantially corresponds to the excitation carrier. said device comprising at least one detection and control module which is functionally active or operational for frequencies of the fault signal from 0 Hz to a few tens of Hz, this module being supplied with power by the network, this module comprising, on the one hand, a measurement torus made of a ferromagnetic material which the aforementioned conductors (2, 2', 2", N) pass through, on the other hand, an excitation circuit for exciting the torus which comprises an AC signal generator which produces a periodic carrier and, finally, a measurement winding which is able and intended to generate a fault signal which results from the appearance of a differential fault in the network, said measurement winding being connected to circuits (7, 8, 9, 10) for processing and evaluating the fault signal and for transmitting a control signal for a breaking or opening means, which also forms part of the differential protection device, the aforementioned circuits (7 to 10) being arranged to form an operational electronic chain which belongs to the detection and control module, which device is characterized in that said operational chain of said module comprises a low-pass or band-pass filtering circuit, which forms the first circuit of said chain and processes the fault signal, or a derived signal (SD') which is directly dependent thereon, in order to extract therefrom the signal component which substantially corresponds to the excitation carrier.