Arc-Resistant design
Arc-Resistant design
(OP)
Can someone please tell me where I can find information on arc-resistant switchgear and it's impact on PPE requirements (if any)? NFPA 70E-2004 does not appear to address arc-resistant design of switchgear. Evidently this design does not reduce the Hazard/Risk Category per NFPA.





RE: Arc-Resistant design
ABB has some good info on its website.
RE: Arc-Resistant design
RE: Arc-Resistant design
I guess I would like to have this blessing come from NFPA rather than the generalities given by the switchgear manufacturers.
RE: Arc-Resistant design
If the switchgear is ANSI-rated and tested for arc-resistance, then it's much more specific than generalities. There are very specific test that the switchgear must pass to be considered arc-resistant. Canada has had standards on this for much longer than ANSI.
Remember that NFPA 70E is a consensus standard, not a legal requirement like the NEC. It doesn't cover every situation.
If you have concerns, I would call NFPA and talk with one of their EEs. They are usually pretty helpful.
RE: Arc-Resistant design
Since NFPA or IEEE does not address arc-resistant gear, my understanding is that arc-resistant gear has no effect on the PPE level.
I have joined the NFPA so that I can talk with one of their EEs, so my $135 dollar question is waiting now for a response.
RE: Arc-Resistant design
Even with arc-resistant switchgear, your approach boundries still apply. Even though 70E is a concensous standard, OSHA is incorporating the standard by reference. If you should ever be unlucky enough to go through an OSHA visit, you better hope the CSHO isn't an electrical expert, because he will cite you multiple times.
RE: Arc-Resistant design
I am going to call the OSHA rep to the 70E commitee and ask but I bet his answer will be "it depends on the region and whom the inspector is", but I will ask.
RE: Arc-Resistant design
Obviously arc-resistant gear increases worker safety, but I do not see an incentive for the significant increase in cost if there is no corresponding decrease in PPE requirements.
Thank you all for your input.
RE: Arc-Resistant design
RE: Arc-Resistant design
The design I mentioned above utilizes a leaky fiber optic cable that is strung within the switchgear compartments. When exposed to the intense light of an arc it initiates instantaneous tripping of the upstream device. It works on the t part of the incident energy calculations, and is therefore addressed by NFPA 70E (you gotta do the calcs and not use the tables). It also works with doors open. Just remember to turn off the flash on your camera.
RE: Arc-Resistant design
OSHA uses NFPA-70E as a guide. Companies are allowed to develop their own safety standards - strict compliance with NFPA-70E is not an OSHA requirement. What OSHA says is that if you comply with NFPA-70E, you will meet OSHA requirements.
Can anyone cite one case where a company was fined for not requiring use of PPE around arc-resistant switchgear when the doors are closed? Or non arc-resistant switchgear, for that matter.
OSHA typically gets involved after an arc-flash incident. If they did happen to question this during a routine inspection, I believe that arc-resistant switchgear would negate the requirement for PPE as long as the doors are closed.
RE: Arc-Resistant design
I like the arc-detection suggestion by stevenal. This definitely reduces the PPE requirements if the upstream device has a fast operate time. And thanks for the tip on using a flash!
RE: Arc-Resistant design
RE: Arc-Resistant design
You're basing your PPE requirements on the task-based table in NFPA-70E. But this table is used **in lieu** of an arc-flash hazard analysis.
If you do an actual analysis and calculate the energy levels, you need to use those results, not the table values.
This same table says that racking a breaker with the doors closed is a Hazard Risk Category #2. But there have been men killed racking breakers with the doors closed (while wearing 100 cal/cm2 flash suits).
The language in NFPA-70E regarding when a hazard exists needs to be improved and clarified - I suspect this will be addressed in the next edition.
The PPE requirements for arc-flash are in a very immature state and will probably be evolving pretty rapidly.
Cheers,
Dave
RE: Arc-Resistant design
This would mean that the switchgear could not even be approached without PPE level 4 - regardless of task!
Thanks dave, I appreciate the discussion.
RE: Arc-Resistant design
You see this addressed in the tables, same equipment has different PPE requirements for different tasks and they are based on risk or odds of an arc flash occuring, the hazard is the same, but the risk is different.
I asked specifically about a situation where a MCC is in an accessable area of a manufacturing plant, the arc flash boundary is lets say 15 feet, do the people walking by that MCC need arc flash protection? The answer I got was "No, as long as they are not operating any equipment and the covers are all on (And screws tight).
RE: Arc-Resistant design
It is interesting (if not actually helpful) to look at some of the definitions in NFPA-70E for things like "exposed", "live parts", etc. And then note that some of these definitions were changed between 2000 and 2004 versions.
Some industrial facilities require PPE to be worn to just walk into electrical rooms.
Most only require PPE if work is being done on or around the equipment. Some require PPE for all switching. Everyone requires PPE for racking breakers (or at least they should).
What if I'm opening the door just to look at something? In most cases, I would say PPE should be worn.
I think at this point, the interpretation is left up to you.