Differential protection device for detecting leakage current or fault current in an electrical installation powered by at least one phase conductor (P1, P2, P3) of a network and at least one neutral and/or earth conductor of said network, said device comprising, on the one hand, a transformer with a preferentially toroidal core made of ferromagnetic material, with a primary winding composed of at least two of the aforementioned conductors (P1, P2, P3, N) and with at least one secondary winding (BS1, BS2) across the terminals of which, or each of which, is established a signal induced when a differential fault occurs at the primary winding and, on the other hand, at least one processing and control circuit designed to process the induced signal and, in the event that a predefined threshold value is exceeded, to control an electromagnetic actuator, a relay or an analogue means for disconnecting or opening the device, said circuit(s) being connected to the terminals of said at least one secondary winding (BS1, BS2), the differential protection device being characterized in that the transformer comprises two separate secondary windings (BS1 and BS2) which form part of two mutually independent electrical circuits, in that the processing and control circuit is connected to the terminals of a first secondary winding, and in that a passive circuit comprising one inductor at least, and at least one resistor and/or at least one capacitor connected in series with said at least one inductor, is connected to the terminals of the second secondary winding, the inductor that forms part of the passive circuit being dimensioned in such a way that, for fault current frequencies greater than approximately 20 kHz, the triggering threshold of the circuit is less than or equal to 420 mA. said device comprising, on the one hand, a transformer with a preferentially toroidal core made of ferromagnetic material, with a primary winding composed of at least two of the aforementioned conductors (P1, P2, P3, N) and with at least one secondary winding (BS1, BS2) across the terminals of which, or each of which, is established a signal induced when a differential fault occurs at the primary winding and, on the other hand, at least one processing and control circuit designed to process the induced signal and, in the event that a predefined threshold value is exceeded, to control an electromagnetic actuator, a relay or an analogue means for disconnecting or opening the device, said circuit(s) being connected to the terminals of said at least one secondary winding (BS1, BS2), the differential protection device being characterized in that the transformer comprises two separate secondary windings (BS1 and BS2) which form part of two mutually independent electrical circuits, in that the processing and control circuit is connected to the terminals of a first secondary winding, and in that a passive circuit comprising one inductor at least, and at least one resistor and/or at least one capacitor connected in series with said at least one inductor, is connected to the terminals of the second secondary winding, the inductor that forms part of the passive circuit being dimensioned in such a way that, for fault current frequencies greater than approximately 20 kHz, the triggering threshold of the circuit is less than or equal to 420 mA.