Methods for limiting arc flash hazards while maintaining system selectivity

Coordination studies utilize time current curves to determine the extent to which upstream overcurrent protective device pick-up and time delays must be increased to provide selectivity with downstream devices. These increases in device time delays result in increased let through energy and greater arc flash hazards. Advanced breaker trip unit technologies, including zone selective interlock, maintenance mode, and enhanced time current curve adjustment options, limit let through energy and reduce arc flash hazards without compromising system selectivity. This paper will detail how these new technologies can be utilized within cement facilities to enhance system reliability and protect personnel.