Circuit breaker and method

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

• a housing having network-side and load-side connections for conductors of the electrical low-voltage circuit;
• a voltage sensor for determining a level of a voltage of the electrical low-voltage circuit;
• a fault current sensor for determining a level of a differential current of the conductors of the electrical low-voltage circuit;
• a mechanical isolating contact unit having contacts being switchable, with a result that an opening of said contacts avoids a current flow and a closing of said contacts allows the current flow in the electrical low-voltage circuit;
• an electronic interruption unit connected in series with said mechanical isolating contact unit on a circuit side and being switched, by means of semiconductor-based switching elements, to a high-impedance state of said semiconductor-based switching elements to avoid the current flow or a low-impedance state of said semiconductor-based switching elements for the current flow in the electrical low-voltage circuit;
• a controller connected to said voltage sensor, said fault current sensor, said mechanical isolating contact unit and said electronic interruption unit, wherein avoidance of the current flow in the electrical low-voltage circuit is switched in if a differential current limit value is exceeded;
• and
• the circuit breaker device is configured such that, when said contacts of the circuit breaker device are closed and said electronic interruption unit has the low-impedance state, said electronic interruption unit comes to have the high-impedance state when a voltage-reduced state of the electrical low-voltage circuit occurs, and that, after leaving the voltage-reduced state, said electronic interruption unit comes to have the low-impedance state again.

A method for operating a circuit breaker device to protect an electrical low-voltage circuit, which comprises the steps of:

• determining a level of a differential current of the electrical low-voltage circuit;
• switching a mechanical isolating contact unit having contacts, with a result that opening of the contacts avoids a current flow and closing of the contacts allows the current flow in the electrical low-voltage circuit;
• switching an electronic interruption unit which is connected in series with the mechanical isolating contact unit on the circuit side, by means of semiconductor-based switching elements, to a high-impedance state of the semiconductor-based switching elements to avoid the current flow or the low-impedance state of the semiconductor-based switching elements for the current flow in the electrical low-voltage circuit;
• comparing a determined level of the differential current with at least one differential current limit value and avoidance of the current flow in the electrical low-voltage circuit is switched if the at least one differential current limit value is exceeded, wherein, when the contacts of the circuit breaker device are closed and the electronic interruption unit has the low-impedance state, the electronic interruption unit comes to have the high-impedance state when a voltage-reduced state of the electrical low-voltage circuit occurs;
• and
• switching the electronic interruption unit to come to have the low-impedance state again after leaving the voltage-reduced state.