A protection system of a railway vehicle traction system includes an electric motor and an electrical power supply circuit. The system further includes: a mechanical coupler between first and second components of a transmission line, the first component being connected to an output shaft of the electric motor and the second component being connected to an input shaft of an axle of the railway vehicle, the coupler being able to be in an engaged or disengaged state; and a controller able to apply a disengagement signal to the coupling signal, to switch from the engaged state to the disengaged state if a failure of the power supply circuit and/or the electric motor is detected.