Risk Analysis or Arc Flash Study?

Q. Is it true that a risk analysis can be performed in place of an arc flash study?

A. An arc flash study is in fact a “risk analysis” if liberally interpreted using NFPA 70E definitions and OSHA regulatory language. Unfortunately, the term “study” has been misinterpreted and misapplied often.

Here’s the bottom line. You must “label” all panels and equipment covered by OSHA regulations (there are three basic exceptions, plus executive decisions for level “0″ panels/equipment). The labels must include the proper PPE to be worn by authorized personnel exposed to potentially dangerous faults. In order to determine what “level” of PPE should be worn, certain electrical calculations must be made. This is where the term “study” comes into play.

If you can grab the electronic files of the coordination and fault study initially completed by the electrical engineer or circuit breaker manufacturer, the costs for printing correct labels can drop significantly.

As an aside, we recently reviewed a case where the breaker settings had been changed to prevent some nuisance trips. Of course, this threw the levels of required PPE into a different universe, making the labels useless. Plus, there was a 2.5MW temporary generator in place whose breaker tripped because of a fault that should have been cleared by a 50A breaker well downstream. “Coordination” was then a moving target, and negated some great planning.

Chisholm, president of MGI Consulting, Orlando, Fla., has provided emergency power supply systems (EPSS) consulting services and education to more than 1,500 health care facilities. He serves as a member of the National Fire Protection Association's Technical Committee responsible for NFPA 110, Emergency and Standby Power Systems and the Electrical Section of NFPA 99, Health Care Facilities. He also serves as a primary emergency power consultant to the U.S. Army Medical Department (AMEDD) and the Department of Defense.

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