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All Posts By

Dave Rewitzer, PE

Dave is a power systems studies engineer and 25-year veteran of the electrical power distribution industry. He specializes in power system studies, short circuit coordination, arc flash hazard assessments, and energy management analysis. An authorized OSHA general industry trainer, Dave teaches arc flash hazard, electrical safety, energy management, & power quality courses. He is a member of IEEE-1584 voting committee and holds a BSEE & MSEE.

Data Center Miscoordination: A Case Study

By Conduit

The NEC requires over current protective devices (OCPD) to protect cables from overheating and catching fire which is achieved using long-time (LT) breaker settings. The NEC also provides guidance on ground fault (GF) and ground fault delay (GFD) settings. Additional settings on OCPDs include long-time delay (LTD), short-time (SD), short-time delay (STD), and instantaneous (I), which can be adjusted and coordinated to protect personnel and equipment from dangerous fault currents. If the only goal was…

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Green Eggs and Blam!

By Conduit

Prior to the 2018 version, NFPA 70E simply cautioned that “greater emphasis may be necessary with respect to de-energizing” equipment with incident energy (IE) exceeding 40 cal/cm2, “when exposed to electrical hazards.” This nebulous direction was applied within the industry by simply labeling everything over 40 cals as “Dangerous – No PPE Exists.” In its new 2018 version, NFPA 70E eliminated this cautionary language. This may lead some to infer that working on energized equipment…

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