In order to dissipate heat losses from the inner conductor (21), the circuit breaker (20) having an elongated inner conductor (21) and an outer conductor (22) which surrounds the inner conductor (21) like a housing has at least one heat pipe (1) which extends from the inner conductor (21) to the outer conductor (22) and has an insulating hollow body (5) in order to form an electrical insulating gap (7). The heat pipe (1) advantageously has a flexibly deformable section (9). The heat pipe (1) can run in a supporting insulator (24) which supports the inner conductor (21). In addition to a working medium, the heat pipe (1) advantageously also contains an auxiliary gas which results in an enhanced dielectric strength at low temperatures.