Improved selective tripping of low-voltage air circuit breakers

SINCE the first devices for interrupting short-circuit currents in electric systems were invented, the problem of having them operate to clear faults without removing energy from normal circuits has existed. Many devices, both separate and as parts of the interrupters, have been developed and good results obtained. Systems having potentials below 600 volts alternating current normally use air interrupting devices designed particularly for this service.