Circuit breaker device

A circuit breaker device for protecting an electric low-voltage circuit, the circuit breaker device comprising:

• a housing having grid-side connections and at least one load-side connection;
• an electronic interruption unit having semiconductor-based switching elements, said electronic interruption unit being associated with said grid-side connections;
• a mechanical isolating contact unit having contacts, said mechanical isolating contact unit having a series connection to said electronic interruption unit, and said mechanical isolating contact unit being associated with said at least one load-side connection;
• said mechanical isolating contact unit configured to be switched by opening said contacts to prevent a current flow or by closing said contacts to allow a current flow in the low-voltage circuit;
• said electronic interruption unit configured to be switched by said semiconductor-based switching elements into a high-resistance state of said semiconductor-based switching elements to prevent a current flow or into a low-resistance state of said semiconductor-based switching elements to allow a current flow in the low-voltage circuit;
• a current sensor unit for determining a current level in the low-voltage circuit;
• a control unit connected to said current sensor unit, to said mechanical isolating contact unit and to said electronic interruption unit, for initiating prevention of a current flow in the low-voltage circuit upon exceeding at least one of current limits or current-time limits;
• and
• a measurement impedance provided between conductors of the low-voltage circuit for causing a measurement current to flow through said electronic interruption unit via said grid-side connections, upon said contacts of said mechanical isolating contact unit being open and said electronic interruption unit being switched to low-resistance.