The use of low voltage current limiting fuses to reduce arc flash energy

Current-limiting fuses, in their current-limiting range, reduce the available short circuit current and clear faults in one-half cycle or less. Available fuse test data, such as let-through l/sup 2/t and peak let-through current, is based upon single-phase bolted-fault tests at full voltage. Currently there is no data available that relates single-phase current-limiting fuse test data with energy released by downstream three-phase arcs. A three-phase 600 V test program was conducted using Class L and RK1 fuses to determine the let-through arc energy and the incident energy produced 18 inches away from a 3-phase arc in a 20 inch cubic box. Incident energy produced by the downstream arc is correlated with the degree of current limitation and fuse bolted-fault test data. The benefit provided by current-limiting fuses in reducing arc flash energy is quantified.