NFPA 70E - PPE / Incident Energy Table

[AWG56]

I am implementing a new electrical safety program compliant to OSHA and NFPA 70E. I want to know how to determine the level of PPE (-1,0,1,2,3,4) based on my incident energy calculations. I have done an extensive arc fault / incident energy survey and I have studied NFPA 70E enough to be able to recite it, but it has a lot of missing pieces.
Does anyone have a table that shows Incident energy (expressed in cal/cm sq.) Vs PPE ?
For example: If a piece of electrical equipment has has an incident energy level of 1.2 cal/cm sq. (18" from face chest). What is the level of PPE needed ?

 

[Zogzog]

Table 130.7(C)(11) of the 2004 70E. And forget about the -1 category, that is going to be removed from the standard soon.

 

[AWG56]

Dear Zogzog,

Thanks for the quick reply but I have to disagree with you.
Table 130.7(C)(11) is the table for selecting the proper clothing - ie. shirt, pants, overalls, flash suit, layering etc.. Not the PPE level.
This table does not correlate to Table 130.7(C)(10).
Article 130.7(C)(11) - Protective Clothing Characteristics - has nothing to do with determining the PPE level. It only defines the "degree of protection for various clothing". Says nothing about eye protection, hand protection, foot protection or shock hazard.
Please read the FPN - of 130.7(C)(12).
I'm looking for a table - or - information that leads me to the level of PPE based on incident energy alone.
Example:
NFPA 70E Annex D.6.2 Arc in a cubic box.
D = 18"
t = .2sec.
F = 20KA
Incident energy = 8.1cal/cm sq.

8 cal/cm sq is a lot of energy at 18".

Example:
A 750KVA transformer 480/277Y secondary @6% imped - bolted fault = 16.2KA

Try dropping a wrench across the live front of a 750KVA trafo and tell me level 2 is OK.

You say Table 130.7(C)(11) is OK to use.

I don't think so.

 

[Zogzog]

Your PPE level is defined by the resultant Ei from your calc, the rating of the clothing used has to be greater that the Ei at the assumed working distance. Of course you must understand the basis of an ATPV and a EBT rating on the clothing ans the differences between those ratings.

Table 130.7(C)(11) defines the minimum arc rating of PPE for different HRC's. If your Ei os 8.1 cal/cm2 then you would need Level 3 PPE, I dont see why you think this is so complicated. Have you read the 70E Handbook, or just the standard?

I have had several conversations with members of the 70E commitee and I sit on commitees with members of the 70E group, this topic has been discussed several times.

The HRC levels are also programmed into your arc flash software (SKM, Easy power). You seem to be using the 70E equations, have you looked at IEEE 1584? I assume you have. IEE 1584 references Table 130.7(C)(11) for defining the HRC.

And I would not have a problem with dropping a wrench across a little 750kVa transformer, because if I was using a wrench it would be insulated in accordance with the 70E standard and I would be wearing level 3 PPE.

 

[AWG56]

Dear ZogZog,

Just got back from vacation, thanks again for reply.
Table 130.7(C)(11) is a table that list the hazard / risk catageory - protective clothing systems - for the incident energy dissipated on a FABRIC - during arc flash. That's all.
I can't believe that 4 cal/cm sq = Level 1 PPE. That's nuts.
Maybe I'm doing something wrong.
Please verify:
I have a 750 KVA transformer - pad mount 34.5KV/480V @ 5.75% imped.
Available Fault current = 16.39KA
AFC=750KVA/1.73x480x.0575

I want to know the PPE required when taking oil samples live - in the secondary compartment - live front.

IEEE Arc Flash Calculator says I have an incident energy of 2.86cal/cm sq. - PPE level 1.

PPE level 1 is not enough.

Am I doing something wrong ?

 

[Zogzog]

Your cals look right, and 2.86cal/cm2 would be level 1 PPE. What makes you think that is not enough? A typical cotton shirt will ignite around 5 cal/cm2. Level 1 PPE requires FR clothing rated at min of 4cal/cm2 so you would have non conductive safety glasses and a class E hard hat, FR coveralls (Jeans are acceptable for level 1 ) class 0 gloves with leather protectors and leather boots with rubber soles.

I assume you did you calc for 18 inches, typically the sample valve is further than that from the live terminations, I see no problem with your conclusion besides the fact I think you are over-thinking the issue.

Scott Peterson
Training Manager
Power Plus Engineering

http://www.epowerplus.com