IEEE 1584 & NFPA 70E

[wbd]

Is there any fundamental differences in the calculations for arc flash hazards between IEEE 1584 & NFPA 70E?

My understanding is that 1584 is the main document for arc flash hazard analysis and 70E puts those to use in tables for safety in the workplace.

The reason for my question is that I was shown some software programs where, for arc flash analysis, you could pick whether it is based on 1584 or 70E. I thought they were the same.

 

[dpc]

NPFA 70E doesn't really specify a calculation method. In Annex D, they give the Ralph Lee equations from his 1982 paper as an example. They also mention the IEEE 1584 standard.

So the "NFPA 70E" equations in the software are probably based on the Lee equations, while the IEEE 1584 equations are obviously based on the IEEE standard.

But above 15 kV, IEEE 1584 I believe uses the Lee equations, so there should be no difference above 15 kV.

Cheers,

Dave

 

[Zogzog]

The 70E Equations (Dcb=sqrt(53xMVAxt)) for example, are much easier to use and also make more assumptions so they tend to be more conservative.

The 1584 equations are more complex, but in most cases I believe, more accurate.

They also both have different limitations as Dave pointed out.

 

[JBD]

NFPA 70E is the law (as enforced by OSHA). 70E says what you should do. Anything in an Annex is reference material only and not enforceable.

IEE1584 is a simply one of several tools that can be used to comply with 70E.

 

[WDeanN]

If the software you are using is SKM, I can say that the 70E equations referred to are Ralph Lee's equation, and the 1584 equations are those developed by the IEEE 1584 Committee.