An apparatus for use in a power delivery system, the apparatus comprising: a DC circuit breaker having first and second terminals and configured to automatically switch from a closed state to an open state during an overcurrent condition; a disconnector switch in series with the DC circuit breaker, the disconnector switch having a first terminal for connecting to a first polarity terminal of a DC power supply, a second terminal for connecting to a second polarity terminal of the DC power supply and a common terminal connected to the first terminal of the DC circuit breaker, the disconnector switch having at least a first position in which the first terminal is connected to the common terminal and a second position in which the second terminal is connected to the common terminal; and an interlock mechanism coupled to the DC circuit breaker and the disconnector switch, the interlock mechanism configured to disable the DC circuit breaker from automatically switching from the closed state to the open state during the overcurrent condition when the disconnector switch is in the second position.

An apparatus for use in a power delivery system, the apparatus comprising: a DC circuit breaker having first and second terminals and configured to automatically switch from a closed state to an open state during an overcurrent condition; a disconnector switch in series with the DC circuit breaker, the disconnector switch having a first terminal for connecting to a first polarity terminal of a DC power supply, a second terminal for connecting to a second polarity terminal of the DC power supply and a common terminal connected to the first terminal of the DC circuit breaker, the disconnector switch having at least a first position in which the first terminal is connected to the common terminal and a second position in which the second terminal is connected to the common terminal; and an interlock mechanism coupled to the DC circuit breaker and the disconnector switch, the interlock mechanism configured to disable the DC circuit breaker from automatically switching from the closed state to the open state during the overcurrent condition when the disconnector switch is in the second position.

A high voltage circuit-breaker comprising a housing defining a volume for an insulating gas, at least two making and breaking (M&B) units arranged therein, each M&B unit comprising a first and second contact element for forming an electrically conductive connection, at least the first contact element is movable along an axially extending switching axis of the high voltage circuit-breaker, and the first contact elements of the at least two M&B units are motion-coupled; a drive device connected to the first contact element of at least one M&B unit and configured for moving the first contact element along the switching axis over a moving distance for separating conductive connections; and a gas damper connected to the first contact element of the at least one M&B unit and configured for damping movement of the first contact element with a damping force increasing in relation to the moving distance.