A circuit breaker (1; 100) comprising: a first dc line (6; 106) electrically connectable to first incoming and outgoing dc lines (8, 10; 108, 110), the first dc line (6, 106) including a first fault-interrupting switch contact system (2; 102) having contacts; and a first switching aid network (12; 112) including: first and second rectifier strings (16a, 16b), each rectifier string having one or more series connected reverse blocking power electronic devices (D1...Dn) that define a first H-bridge rectifier having first and second dc input terminals (22a, 22b) and first and second dc output terminals (24a, 24b), the first and second dc input terminals (22a, 22b) being connected to the first dc line (6; 106) in parallel with the first fault-interrupting switch contact system (2; 102), and a snubber string having one or more series connected power electronic devices (T1...Tn) capable of being turned on by gate control, the snubber string being connected between the first and second dc output terminals (24a, 24b) of the first H-bridge rectifier, characterised by the first switching aid network further including: a pre-charge string having one or more series connected power electronic devices (T1...Tn) capable of being turned on by gate control and a first resistor, the pre-charge string being connected between the first and second dc output terminals (24a, 24b) of the first H-bridge rectifier, and a surge arrester connected between the first and second dc output terminals (24a, 24b) of the first H-bridge rectifier, wherein the snubber string further comprises a capacitor connected in series with the power electronic devices (T1...Tn) of the snubber string. a first dc line (6; 106) electrically connectable to first incoming and outgoing dc lines (8, 10; 108, 110), the first dc line (6, 106) including a first fault-interrupting switch contact system (2; 102) having contacts; and a first switching aid network (12; 112) including: first and second rectifier strings (16a, 16b), each rectifier string having one or more series connected reverse blocking power electronic devices (D1...Dn) that define a first H-bridge rectifier having first and second dc input terminals (22a, 22b) and first and second dc output terminals (24a, 24b), the first and second dc input terminals (22a, 22b) being connected to the first dc line (6; 106) in parallel with the first fault-interrupting switch contact system (2; 102), and a snubber string having one or more series connected power electronic devices (T1...Tn) capable of being turned on by gate control, the snubber string being connected between the first and second dc output terminals (24a, 24b) of the first H-bridge rectifier, characterised by the first switching aid network further including: a pre-charge string having one or more series connected power electronic devices (T1...Tn) capable of being turned on by gate control and a first resistor, the pre-charge string being connected between the first and second dc output terminals (24a, 24b) of the first H-bridge rectifier, and a surge arrester connected between the first and second dc output terminals (24a, 24b) of the first H-bridge rectifier, wherein the snubber string further comprises a capacitor connected in series with the power electronic devices (T1...Tn) of the snubber string. first and second rectifier strings (16a, 16b), each rectifier string having one or more series connected reverse blocking power electronic devices (D1...Dn) that define a first H-bridge rectifier having first and second dc input terminals (22a, 22b) and first and second dc output terminals (24a, 24b), the first and second dc input terminals (22a, 22b) being connected to the first dc line (6; 106) in parallel with the first fault-interrupting switch contact system (2; 102), and a snubber string having one or more series connected power electronic devices (T1...Tn) capable of being turned on by gate control, the snubber string being connected between the first and second dc output terminals (24a, 24b) of the first H-bridge rectifier, a pre-charge string having one or more series connected power electronic devices (T1...Tn) capable of being turned on by gate control and a first resistor, the pre-charge string being connected between the first and second dc output terminals (24a, 24b) of the first H-bridge rectifier, and a surge arrester connected between the first and second dc output terminals (24a, 24b) of the first H-bridge rectifier, wherein the snubber string further comprises a capacitor connected in series with the power electronic devices (T1...Tn) of the snubber string.