Additional electrical-fault-detection module configured to be attached to an electrical protection device comprising at least: - a housing in modular format, - a first output connection terminal, - a second output connection terminal, - a first electrical line comprising a first connection end which is connected to the first output connection terminal and a second connection end intended to be electrically connected to said electrical protection device or to an electrical installation upstream of the electrical protection device, - a second electrical line comprising a third connection end which is connected to the second output connection terminal and a fourth connection end intended to be electrically connected to said electrical protection device or to an electrical installation upstream of the electrical protection device, - a differential-fault measurement toroid traversed by the first electrical line and the second electrical line, - optionally an electrical-arc-fault measurement toroid, preferably traversed only by the first electrical line, - an electronic unit electrically connected on the one hand to the differential-fault measurement toroid and where applicable to the electrical-arc-fault measurement toroid configured at least to process on the one hand a first signal measured by the differential-fault measurement toroid and where applicable on the other hand a second signal measured by the electrical-arc-fault measurement toroid, the housing comprising a connection compartment accommodating the first output connection terminal and the second output connection terminal, the additional electrical-fault-detection module is characterized in that the differential-fault measurement toroid is contained in the connection compartment and in that the electronic unit and where applicable the electrical-arc-fault measurement toroid are arranged in the housing outside the connection compartment. - a housing in modular format, - a first output connection terminal, - a second output connection terminal, - a first electrical line comprising a first connection end which is connected to the first output connection terminal and a second connection end intended to be electrically connected to said electrical protection device or to an electrical installation upstream of the electrical protection device, - a second electrical line comprising a third connection end which is connected to the second output connection terminal and a fourth connection end intended to be electrically connected to said electrical protection device or to an electrical installation upstream of the electrical protection device, - a differential-fault measurement toroid traversed by the first electrical line and the second electrical line, - optionally an electrical-arc-fault measurement toroid, preferably traversed only by the first electrical line, - an electronic unit electrically connected on the one hand to the differential-fault measurement toroid and where applicable to the electrical-arc-fault measurement toroid configured at least to process on the one hand a first signal measured by the differential-fault measurement toroid and where applicable on the other hand a second signal measured by the electrical-arc-fault measurement toroid, the housing comprising a connection compartment accommodating the first output connection terminal and the second output connection terminal, the additional electrical-fault-detection module is characterized in that the differential-fault measurement toroid is contained in the connection compartment and in that the electronic unit and where applicable the electrical-arc-fault measurement toroid are arranged in the housing outside the connection compartment.