Low voltage circuit breaker coordination
NEMA publishes “NEMA AB 5 Establishing Levels of Selective Coordination for Low Voltage Circuit Breakers.”
Rosslyn, Va.—The National Electrical Manufacturers Association (NEMA) has published “NEMA AB 5 Establishing Levels of Selective Coordination for Low Voltage Circuit Breakers.”
AB 5-2011 examines selective coordination at high levels of short circuit fault current in the instantaneous region of the circuit breaker time-current curve by use of selective coordination tools. NEMA AB 5 includes molded case circuit breakers and insulated case circuit breakers, specifically instantaneous selective coordination at high levels of fault current. The intent of this standard is to ensure that circuit breaker manufacturers are consistent in the methods they use in validating the information that is published in selective coordination tools.
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