Device for detecting an insulation fault

The device (4) has a first current limiting circuit (41) connected between a first input terminal (47) and an intermediate point (49). A second current limiting circuit (42) is connected between a second input terminal (48) and the point. An insulation fault current detection circuit (45) is connected between an electric ground (93) and the point. The limiting circuits selectively open and close the connection between the respective terminals and the point. A control circuit (8) simultaneously maintains one of the limiting circuits in open state and the other limiting circuit in closed state. The control circuit is formed by a battery operation supervision controller. An independent claim is also included for a motorization system.