Differential protection device which makes it possible to detect a fault or leakage current in an electrical installation supplied with power 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 core, which is preferably toroidal, made of ferromagnetic material, with a primary composed of at least two of the aforementioned conductors (P1, P2, P3, N) and with one or more secondary windings (BS1, BS2), at the terminals of which secondary winding or of each of which secondary windings a signal induced upon the occurrence of a differential fault at the primary is established 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, control an electromagnetic actuator, a relay or an analogous breaking or opening means of the device, said circuit or circuits being connected to the terminals of said at least one secondary winding (BS1, BS2), which differential protection device is characterized in that the transformer comprises two secondary windings (BS1 and BS2) with a common point, in that a passive circuit comprising at least one inductor, as well as at least one resistor and/or at least one capacitor in series, is connected to the terminals of at least one of the secondary windings (BS1, BS2) and in that said processing and control circuit and said passive circuit are arranged and connected in such a way: - that one of these two circuits (ETC and CP) is connected, on the one hand, to the common point and, on the other hand, to the terminal, which is not connected to the common point, of a first of the two secondary windings (BS1 and BS2) and - that the other of these two circuits (ETC and CP) is either connected to each of the terminals (BBS1, BBS2) of the secondary windings (BS1 and BS2) which is not connected to the common point or connected, on the one hand, to the common point and, on the other hand, to the terminal, which is not connected to the common point, of the second of the two secondary windings (BS1 and BS2), the inductor forming part of the passive circuit advantageously being sized in such a way that, for fault current frequencies greater than about 20 kHz, the trip threshold of the circuit is less than or equal to 420 mA. said device comprising, on the one hand, a transformer with a core, which is preferably toroidal, made of ferromagnetic material, with a primary composed of at least two of the aforementioned conductors (P1, P2, P3, N) and with one or more secondary windings (BS1, BS2), at the terminals of which secondary winding or of each of which secondary windings a signal induced upon the occurrence of a differential fault at the primary is established 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, control an electromagnetic actuator, a relay or an analogous breaking or opening means of the device, said circuit or circuits being connected to the terminals of said at least one secondary winding (BS1, BS2), which differential protection device is characterized in that the transformer comprises two secondary windings (BS1 and BS2) with a common point, in that a passive circuit comprising at least one inductor, as well as at least one resistor and/or at least one capacitor in series, is connected to the terminals of at least one of the secondary windings (BS1, BS2) and in that said processing and control circuit and said passive circuit are arranged and connected in such a way: - that one of these two circuits (ETC and CP) is connected, on the one hand, to the common point and, on the other hand, to the terminal, which is not connected to the common point, of a first of the two secondary windings (BS1 and BS2) and - that the other of these two circuits (ETC and CP) is either connected to each of the terminals (BBS1, BBS2) of the secondary windings (BS1 and BS2) which is not connected to the common point or connected, on the one hand, to the common point and, on the other hand, to the terminal, which is not connected to the common point, of the second of the two secondary windings (BS1 and BS2), - that one of these two circuits (ETC and CP) is connected, on the one hand, to the common point and, on the other hand, to the terminal, which is not connected to the common point, of a first of the two secondary windings (BS1 and BS2) and - that the other of these two circuits (ETC and CP) is either connected to each of the terminals (BBS1, BBS2) of the secondary windings (BS1 and BS2) which is not connected to the common point or connected, on the one hand, to the common point and, on the other hand, to the terminal, which is not connected to the common point, of the second of the two secondary windings (BS1 and BS2), the inductor forming part of the passive circuit advantageously being sized in such a way that, for fault current frequencies greater than about 20 kHz, the trip threshold of the circuit is less than or equal to 420 mA.