A type B or B+ differential protection device allowing the detection of leakage or fault current in an electrical installation supplied by a least two phase conductors of a network or by at least one phase conductor of a network and by one neutral conductor of said network, said device including two distinct detection and control modules (3 and 3') each comprising at least one signal processing stage (4, 4') able and intended, on the one hand, to exploit a fault signal generated by the appearance of a differential fault at said network and, on the other hand, to control an electromagnetic actuator, relay or means for breaking or opening the device when said fault signal exceeds a frequency-dependent predefined threshold value, each of said detection and control modules (3, 3') being functionally active or operational over its own specific frequency range, the two modules (3 and 3') being independent of each other and arranged so as to constitute two parallel and mutually independent detection channels, controlling the same actuator, relay or breaking means, in that the second module of the two modules (3, 3') being autonomous in terms of power supply, and in particular not depending on the voltage of the network or of the sector, and each module (3, 3') being connected to its own specific means (6, 6') for delivering a fault signal, the device characterized: in that a first of the two modules (3, 3') is a detection and control module which is functionally active or operational for frequencies of the fault signal from 0Hz to a few tens of Hz, this first module being supplied by the network, in that the second of the two modules (3, 3') is a detection and control module which is functionally active or operational for frequencies of the fault signal of a few tens of Hz to at least 1 kHz, in that the frequency domains of operational functioning of the two modules (3 and 3') mentioned above being partially overlapping, and in that the curves (C and C') of variation of the current sensitivity as a function of the frequency of the two modules (3 and 3') respectively, present a common point of intersection, the value of the frequency of this point being at most equal to the value of the frequency of the monitored network or of the sector. said device including two distinct detection and control modules (3 and 3') each comprising at least one signal processing stage (4, 4') able and intended, on the one hand, to exploit a fault signal generated by the appearance of a differential fault at said network and, on the other hand, to control an electromagnetic actuator, relay or means for breaking or opening the device when said fault signal exceeds a frequency-dependent predefined threshold value, each of said detection and control modules (3, 3') being functionally active or operational over its own specific frequency range, the two modules (3 and 3') being independent of each other and arranged so as to constitute two parallel and mutually independent detection channels, controlling the same actuator, relay or breaking means, in that the second module of the two modules (3, 3') being autonomous in terms of power supply, and in particular not depending on the voltage of the network or of the sector, and each module (3, 3') being connected to its own specific means (6, 6') for delivering a fault signal, the device characterized: in that a first of the two modules (3, 3') is a detection and control module which is functionally active or operational for frequencies of the fault signal from 0Hz to a few tens of Hz, this first module being supplied by the network, in that the second of the two modules (3, 3') is a detection and control module which is functionally active or operational for frequencies of the fault signal of a few tens of Hz to at least 1 kHz, in that the frequency domains of operational functioning of the two modules (3 and 3') mentioned above being partially overlapping, and in that the curves (C and C') of variation of the current sensitivity as a function of the frequency of the two modules (3 and 3') respectively, present a common point of intersection, the value of the frequency of this point being at most equal to the value of the frequency of the monitored network or of the sector. in that a first of the two modules (3, 3') is a detection and control module which is functionally active or operational for frequencies of the fault signal from 0Hz to a few tens of Hz, this first module being supplied by the network, in that the second of the two modules (3, 3') is a detection and control module which is functionally active or operational for frequencies of the fault signal of a few tens of Hz to at least 1 kHz, in that the frequency domains of operational functioning of the two modules (3 and 3') mentioned above being partially overlapping, and in that the curves (C and C') of variation of the current sensitivity as a function of the frequency of the two modules (3 and 3') respectively, present a common point of intersection, the value of the frequency of this point being at most equal to the value of the frequency of the monitored network or of the sector.