When an electric current passes through air between ungrounded conductors or between ungrounded and grounded conductors, the temperatures can reach 35000F.
Exposure to these extreme temperaturs both burns the skin and causes the ingnition of clothing. Each year more than 2000 people are admitted to burncenters with severe arc-flash burns.
An arc-flash can and do kill at distances 10ft or greater.
Source: NFPA 70E-2004, Annex K.3
According to the title of the NFPA 70E standard it is the “Standard for Electrical Safety in the Workplace”. And that is just what it is. Now the better question would have been, do I need to understand NFPA 70E in my workplace?
Or how does NFPA 70E apply to me?
The typical workplaces that are covered by NFPA 70E are buildings, utilities, yards, parking lots, etc. However it does not cover ships, watercraft, underground mine installations, communication equipment and installations that are under the exclusive control of the electric utility.
In the last few years, NFPA 70E has been known synonymously with Arc Flash and Arc Flash PP. However that is only a small part of the standard in the whole. Arc Flash and Arc Flash PPE are covered only in Article 130, Working On or Near Live Parts. It is in this section that NFPA 70E talks about Limited Approach Boundarys as based on System Votage (Table 130.2(C)), the Protective Clothing and PPE Matrix (Table 130.7(C)(10)) and has many other useful tables to help to educate how to work on live equipment in the safest manner.
In fact if you go to the index the only place that the term Arc Flash is used is in Annex K. It is here where you can find a definition of what Arc Flash is, and the difference between Arc Flash and Arc Blast.
Some of the topics that NFPA 70E do discuss in depth is how to do maintence in different situations including Hazardous Locations, rotating equipment, Battery Rooms, and the PPE required in these situations. One thing the NFPA 70E stresses is that PPE is a last line of defense. Whenever possible Electrically and Mecahnically isolated the system that you or your employee is going to work on.
Finally NFPA 70E has great information in its Annexes. Some of this includes establishing a “Electrical Safety Program”, “Job Briefing and Planning Checklist” and “Cross reference Tables”.
If you work on energized equipment, even if it is only once a month or less. NFPA 70E will be evaluable to you in educating yourself and others on the risks involved and how to mitigate them most reasonably.
Finally if you liked this article or have questions please leave a comment.
Welcome to the site. Sparky Resource is my pet project to discuss Arc Flash and all related matters. I will be posting articles about NFPA, IEEE and other related materials. Solutions, problems and news.
I hope to discuss the topic with little if any “sales prejudice” since I am a consulting engineer for a medium sized General Engineering firm. I will discuss different presentations that I have been to that were given by fuse manufacturers, breaker manufacturers and try to point out the prejudices that are evident in what they say, and why you have to take everything that people tell you as defintes regarding Arc Flash with a grain of salt.
There will be some articles that will be technical in nature, so if you are reading this and don’t understand something please be sure to make a comment asking for clarification. I will do my best to help you fulling understand the topics.
