70E 130.7 (C) requires an employee "working" within the Arc Flash Boundary to where the proper PPE.

Question: What is the definition of work? Opening a 600V switch with the panels on?Thermal imaging? We all know tasks requiring that the covers be removed is work that warrants wearing the PPE - that on is easy.

I ask because table 130.7(C)(9) calls out work procedures and corresponding PPE categories "IF" there has been no arc flash analysis performed. I've done the analysis and have the incident energy levels but cannot find a document that defines what work procedures require the PPE to be worn.

For example, I have a 2000A (480V) switch with 700 plus cal/cm2 available. I believe (if I remember correctly) that the table calls out operating a 600V rated switch with the covers in place as a risk category 0. Yet, in my system there is no risk category applicable - it must be worked on de-energized. But once again, what is the definition of work?

Thanks for all input!

See Article 100 definition of Arc Flash Hazard. FPN No. 1 says it may exist when "a person is interacting with the equipment in such a manner that could cause an electric arc." There has been a lot of discussion in this forum as to what that means. I think a good rule, based on FPN No. 2, would be that if anyone is performing a task that has a HRC > 0 in Table 130.7(C)(9), then anyone within the arc flash boundary has to wear PPE.

No free ride by deenergizing. Deenergization must be confirmed by test, and testing is an interaction with equipment presumed to be energized.

If your switch gives you 700 cal/cm2, then you most probably can't use table 130.7(C)(9) because of the fault current or the clearing time (see the corresponding note at the end of the table). Which means it's not a HRC 0.

Work

The way I interrupt WORK for my company has two meanings. 1) Diagnostic - your only looking visually or testing as a qualified worker and no physical contact with anything other then meter probes or test instruments. Or you are outside the boundaries again viewing only. You still wear the PPE inside the boundary as determined by the studies label as a guide not a right to work. 2) Manipulative (physical work) work that involves the touching, installing, moving, pulling in wire, etc. Any other physical work in or around exposed devices other then diagnostics and within the boundary is manipulative work and not allowed without a job brief and work permit. Some one may tell me if I am missing the point. I’m not sure this helps with your question.

Happening to be in the Boundary while employed (IMO).

If an employee is simply loafing about, but in the AFB they need to be protected.

If the IE is 700 cal/cm2 then the category is dangerous, no ppe exists for that available energy. It mustbe worked on deenergized. Work would include anything that could cause an arc to start, including just opening the panel.

How do you test to verify it is deenergized if no PPE exists? Bomb squad robot?

I think you need to look at how your study was done. 700cal/cm2 on a 2000A 480V switch is very unlikely correct. With conditions that would give you anything near 799cal you would not be able to use the tables anyways.

Article 100

NFPA 70E 2009 Article 100 defines "Working On" in very simple terms. It is defined as: "Coming in contact with energized electrical conductors or circuit parts with the hands, feet, or other body parts, with tools, probes, or with test equipment, regardless of the personal protective equipment a person is wearing." It is further broken down into 2 categories; Diagnostic Testing and Repair.

Catch 22

Here's the Catch 22. If we are to assume every electrical part is energized until proven otherwise (with a meter) what PPE should be worn to verify this 2000A bus is deenergized? I also do not believe it is 700 cal/cm^2. A 2000kVA transformer with 5.75% impedance would only have 41kA fault current with an infinite source. I would believe 70 cal/cm^2 which is still > CAT #4 or energized work prohibited.

If the high IE is on the secondary of a transformer or the line side of a main breaker protected only by high side fuses, would de-energizing the primary and testing the primary be acceptable? The primary is usually much lower IE.

Is having a one-line diagram sufficient to ensure that the primary of the transformer is the only source of power to the main breaker?

There should be a LOTO procedure for that main breaker, follow it.

How old and how accurate is the diagram? NFPA 70E says to check applicable up-to-date drawings, diagrams, and ID tags. Tie breakers and ATS's are usually going to be the culprits for multiple feeds. Loop distribution systems can also be quite complex.

Verifying downstream of the main breaker does not assure that there is no voltage on the line side of the main breaker. Something downstream may be disconnected. The main breaker or feeder breaker may be open (maybe failed with open contacts).