In one aspect, a breaker circuit arranged to isolate a converter (300, 400, 500) from a direct current network (204) in the event of a fault condition is described. The breaker circuit comprises an isolation element (104) such as a mechanical switch arranged, on activation, to prevent current flow between the network (204) and the converter (300, 400, 500) and an energy absorption element (1 12, 414, 556), capable of receiving energy remaining in the circuit following activation of the isolation element (104). Also provided is a commutating voltage source (106, 206, 570) arranged to provide a source of commutating voltage to divert current away from the isolation element (104) and a switchable isolation element bypass path (1 10) arranged to the receive the diverted current. At least one of the energy absorption element (1 12, 414, 556), the commutating voltage source (106, 206, 570) and the isolation element bypass path (1 10) is operable in a non-fault condition to provide a functional component of the converter. Converters and methods of operation thereof are also described.