Current limiting for low voltage, high current applications

A pyrotechnic current-limiting interrupter (CLI) has been developed for use in high-current 60 Hz 480 V three-phase electrical bus circuits. The interrupter design combines a high continuous current rating (4800 A r.m.s.) with a high current interruption capability (210 kA r.m.s. symmetrical). Its electrical power loss is low and its mechanical construction uses no complex moving mechanisms. The CLI is used with a current sensor, electronic logic, and energy storage circuitry. the current sensor continuously monitors the current through and CLI and provides input to logic circuits which analyze and determine the validity of the fault condition. Both the fault current magnitude and rate of current increase are used in combination to make the decision when to activate the CLI. Using stored electrical energy, a detonator is activated causing an explosive cord to generate shock waves sufficient to cut the current-carrying conductors. Detection and initiation of the interruption process occurs within 1/4 cycle for a symmetrical fault and within 1/2 cycle for an asymmetrical fault. The first peak in the fault current is limited to the first half-cycle