Device for detecting a direct or alternating electric fault current (If), comprising: - a direct current sensor, comprising: - a first magnetic circuit which has at least one current conductor through which the electric fault current (If) to be detected flows passing through it, said current conductor forming a first primary circuit, - a first winding coiled about said first magnetic circuit in order to form a first secondary circuit and produce a first signal which is representative of the fault current (If), and - a generator connected to the terminals of the first winding in order to generate an alternating current (Ig) for exciting the first magnetic circuit and to induce a magnetic field in the first magnetic circuit, and - a current measurement circuit, and - an alternating current sensor, comprising a second magnetic circuit about which a second winding is coiled in order to produce a second signal which is representative of the fault current (If) flowing through the current conductor, characterized in that said second winding is connected in series with the first winding so that the first signal and the second signal (Is1, Is2) which are representative of the fault current (If) flowing through the current conductor are in phase, and with the current measurement circuit, the second magnetic circuit having the current conductor through which the electric fault current (If) flows passing through it, said current conductor forming a second primary circuit, and said generator is arranged in order for the magnetic field to saturate the first magnetic circuit alternately in a given direction and then in the opposite direction. - a direct current sensor, comprising: - a first magnetic circuit which has at least one current conductor through which the electric fault current (If) to be detected flows passing through it, said current conductor forming a first primary circuit, - a first winding coiled about said first magnetic circuit in order to form a first secondary circuit and produce a first signal which is representative of the fault current (If), and - a generator connected to the terminals of the first winding in order to generate an alternating current (Ig) for exciting the first magnetic circuit and to induce a magnetic field in the first magnetic circuit, and - a first magnetic circuit which has at least one current conductor through which the electric fault current (If) to be detected flows passing through it, said current conductor forming a first primary circuit, - a first winding coiled about said first magnetic circuit in order to form a first secondary circuit and produce a first signal which is representative of the fault current (If), and - a generator connected to the terminals of the first winding in order to generate an alternating current (Ig) for exciting the first magnetic circuit and to induce a magnetic field in the first magnetic circuit, and - a current measurement circuit, and - an alternating current sensor, comprising a second magnetic circuit about which a second winding is coiled in order to produce a second signal which is representative of the fault current (If) flowing through the current conductor, said second winding is connected in series with the first winding so that the first signal and the second signal (Is1, Is2) which are representative of the fault current (If) flowing through the current conductor are in phase, and with the current measurement circuit, the second magnetic circuit having the current conductor through which the electric fault current (If) flows passing through it, said current conductor forming a second primary circuit, and said generator is arranged in order for the magnetic field to saturate the first magnetic circuit alternately in a given direction and then in the opposite direction.