Selective Coordination of Electrical Over Current Protection
Bernie Wright, General Electric
Thursday, 20 November 2008 at 6:30 PM
Clark-Nexsen
6160 Kempsville Circle, Suite 200A
Norfolk, VA 23502
+1 757.455.5800
Meal Cost (Pizza and soft drinks): Members and guests $5; Students FREE
Presentation: Free
The National Electric Code (NEC) defines selective coordination as the “localization of an over current condition to restrict outages to the circuit or equipment affected, accomplished by the choice of over current protective devices and their ratings or settings.” In a well-coordinated electrical system faults are isolated by having only the closest upstream breaker or fuse operate, leaving the rest of the electrical system in operation. Selective coordination requirements have increased with successive revisions of the NEC (NFPA-70) and as of 2008 cover 5 scenarios: health care facility essential systems, multi-elevator systems, emergency systems, legally-required standby systems and critical operation power systems. Achieving selective coordination requires the design engineer to carefully study the ratings of numerous components, as well as coordinate with the electric utility to understand the characteristics of the supply system.
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