This article is the second in a series that provides a step-by-step approach for performing arc flash calculations. The first part, “A Calculated Introduction,” appeared in the January 2016 issue of ELECTRICAL CONTRACTOR.
Arcing short-circuit currents
“Don’t touch that dial” is an old phrase from the 1960s television era that an announcer would say just before “Batman” or another program cut to a commercial. They would pronounce it so authoritatively that you wouldn’t dare change the channel.
“Properly” and “Maintained”—these two words always come up when discussing arc flash hazards. Why? Because protective devices such as circuit breakers and relays that have not been properly maintained may not operate as quickly as they should.
There are many frequently asked questions about performing an arc-flash study (risk assessment) and understanding electrical safety requirements. A careful read of standards such as NPFA 70E or IEEE 1584 can answer some questions. Yet, other questions can be more complex.
I’ve heard it all before. “What were they thinking when they wrote this standard? If I were them, this is how I would have done it.” When it comes to arc flash and electrical safety standards, complaints, armchair quarterbacking and second-guessing follow as soon as the latest edition comes out.
This article expands on “Control the Risk” (ELECTRICAL CONTRACTOR, March 2015). It addresses six key areas in the risk-control hierarchy and how each can be used to reduce the risk associated with the arc flash hazard.
On Jan. 12, 2015, passengers on a Washington Metropolitan Transit Authority (WMATA) Metrorail train were trapped for some 40 minutes in the tunnels between two downtown D.C. stations, while smoke filled the air, according to the Washington Post.
New Year’s Resolutions are easy to make but difficult to keep. There is still time to make a few late resolutions. Here are 10 such resolutions for electrical safety that should be made (and kept) for 2015. They may just save a life.
Obtain the 2015 edition of NFPA 70E
Everyone tenses up in anticipation as they hear the countdown, “three, two, one.” Then there’s an extremely loud BOOM and blinding light. Sparks fly everywhere, and smoke fills the test area. Laughter and perhaps even a high five frequently follow.
Edward Murphy is famous for his law that states: “Anything that can go wrong will go wrong.” When performing an arc flash study, Murphy’s Law becomes very important if assumptions are made about this rare but potentially deadly event.
The first step in conducting an arc flash study is to obtain the data necessary to accurately represent the electrical system. Equations defined by IEEE 1584–IEEE Guide for Performing Arc Flash Hazard Calculations are at the heart of most studies and require a lot of data.
Without warning, smoke rolled out from under the tires as they squealed against the pavement with the brakes locked up. The big truck seemed to come from nowhere. It felt like an eternity; although it was really only a matter of seconds, then … CRASH!
The surface area of the earth is approximately 197 million square miles, and IEEE 1584—IEEE Guide for Performing Arc-Flash Hazard Calculations has been covering more of it every day since it was first published almost 11 years ago.