CIRCUIT BREAKER AND METHOD

A circuit breaker protecting an electric low-voltage circuit includes grid-side and load-side connections for low-voltage circuit conductors, a mechanical isolating contact unit having a closed contact state for current flow or an open contact state for DC isolation preventing current flow in the low-voltage circuit. An electronic interruption unit series-connected to the isolating contact unit has a high-ohmic state of switching elements preventing current flow or a low-ohmic state allowing current flow in the low-voltage circuit. The current level of the low-voltage circuit is ascertained, and upon exceeding current limit values or current/time limit values, current flow in the low-voltage circuit is prevented. After preventing current flow by a high-ohmic state of the switching elements and closed state of the contacts, at least one electric parameter at least at one load-side connection is checked.