Use of Specific Purpose Fuses for Mitigation of ARC Flash Hazard

Abstract

In certain circumstances, the calculated arc flash potential for components downstream of a circuit breaker can be extraordinarily high, due to the worst case condition for arc flash falling in an area of the breaker trip curve where instantaneous protection is not assured. In certain cases, addition of fuses that are rated significantly above the circuit breaker trip value in series with the circuit breaker can reduce the arc flash potential significantly. These fuses do not significantly affect the trip coordination of the system, since they will only actuate when there is a severe fault, such as a bolted short circuit fault or a fault sufficiently severe as to present an arc flash hazard. This paper examines an applicable case, using trip curves to analyze the arc flash potential, and reducing arc flash from above 15 cal/cm2 to below 1.2 cal/cm2 by addition of fuses.