US Patent 8227721 Power line current interrupter having a vacuum switch chamber

This interrupter device includes a parallel branch (4) in which a vacuum switch chamber is connected for breaking current. The branch is inactive in normal operation, with current flowing in it only when the disconnector (2) has started its opening movement, by progressive transfer of the current from the main power line (1) to the branch (4). Since the vacuum switch (6) is generally at rest, it no longer needs to be dimensioned to satisfy stringent electrical and dielectric requirements for normal operation.