A hybrid circuit breaker for interrupting fault currents comprises a mechanical switch (31) through which a normal current is passed, the mechanical switch being arranged to open in case of being exposed to a fault current; and a semiconductor breaker device (32) to which the fault current is commutated, the semiconductor breaker device being arranged to break the fault current. The mechanical switch has a contact arm (33) with two contacts (33a-b) abutting stationary contacts (34a-b) of a circuit when being closed, wherein the two contacts of the contact arm are located at different distances (x1, x2) from the axis of rotation such that the separations (z1, z2) between the two contacts of the contact arm and the two stationary contacts are different when the mechanical switch opens. The semiconductor breaker device is connected in parallel with the contact (33b) of the contact arm and the stationary contact (34b) which separate most when the mechanical switch opens.