A device for monitoring and protecting equipment powered by at least one solid-state power controller called SSPC (5, 6, 7), said device including at least one current measurement circuit characterised in that it includes: - a current measuring transformer receiving at the primary at least the three phases (1, 2, 3) of a three-phase power supply of the equipment or the phase and the neutral of a single-phase power supply of the equipment and provided at the secondary with at least two windings (13, 14) for measuring the current at the primary, - a measuring and testing module including a measuring and testing controller provided with at least one analog input (10a, 11a) connected to at least one of said measurement windings (13, 14) by a measurement channel (10, 11) for measuring a current at the secondary I m, representative of a differential current I d at the primary and provided with a measurement program and a digital channel for communication with said SSPC for controlling a switch of said SSPC in the event that said current I d exceeds a given threshold; wherein said module includes a channel for injecting current into said transformer, said channel comprising a current I inj generator controlled by an output of the measuring and testing controller and connected to an injection winding on said transformer, said injection winding including a number of turns N inj adapted so that the current I inj produces in said measurement windings (13, 14) a test current I m of said secondary in the absence of current at the primary characterized in that said module includes a test program adapted to control a current injection in parallel with a current measurement; and wherein said two measurement windings (13, 14) at the secondary are such that a first measurement winding is adapted for a measurement of a leakage current at the primary in a range 0 to 100 milliamps and a second measurement winding is adapted for a measurement of a leakage current at the primary in a range of 0 to 2 amps. - a current measuring transformer receiving at the primary at least the three phases (1, 2, 3) of a three-phase power supply of the equipment or the phase and the neutral of a single-phase power supply of the equipment and provided at the secondary with at least two windings (13, 14) for measuring the current at the primary, - a measuring and testing module including a measuring and testing controller provided with at least one analog input (10a, 11a) connected to at least one of said measurement windings (13, 14) by a measurement channel (10, 11) for measuring a current at the secondary I m, representative of a differential current I d at the primary and provided with a measurement program and a digital channel for communication with said SSPC for controlling a switch of said SSPC in the event that said current I d exceeds a given threshold; wherein said module includes a channel for injecting current into said transformer, said channel comprising a current I inj generator controlled by an output of the measuring and testing controller and connected to an injection winding on said transformer, said injection winding including a number of turns N inj adapted so that the current I inj produces in said measurement windings (13, 14) a test current I m of said secondary in the absence of current at the primary characterized in that said module includes a test program adapted to control a current injection in parallel with a current measurement; and wherein said two measurement windings (13, 14) at the secondary are such that a first measurement winding is adapted for a measurement of a leakage current at the primary in a range 0 to 100 milliamps and a second measurement winding is adapted for a measurement of a leakage current at the primary in a range of 0 to 2 amps.