Abstract: A commutation type DC breaker having a commutation circuit electrically connected in parallel to a main contact. The main contact is connected between a DC power supply and a load. The commutation circuit is a series circuit of a commutation capacitor, a reactor and a commutation switch, with an energy absorption device electrically connected in parallel to the main contact. A switch or a breaker for preventing the flow of commutation current from the commutation circuit to the load in a non-load opening mode is connected between an electrical connection point (P), of the main contact and the commutation circuit, and the load and is opened substantially simultaneously with the opening of the main contact, or before the closure of the commutation switch. In this manner, the safety on the load in the non-load opening mode is enhanced.

Abstract: A commutating type DC circuit breaker arrangement comprising: a vacuum circuit breaker having a movable electrode and stationary electrode; a series circuit of a capacitor, a saturation reactor and a commutating switch which is connected in parallel with the vacuum circuit breaker; and an electrical relay for detecting a predetermined electrode open position at which a sufficient insulating distance between the movable electrode and the stationary electrode is maintained via movement of a predetermined position on an actuating rod for the movable electrode and for closing the commutating switch in response to the detection of the predetermined electrode open position.