Arc-Resistant design

[Brimy]

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.

 

[Zogzog]

You are right, it is not addressed. The goal of arc resistant switchgear designs or retrofits is to eliminate the arc fash hazard.

ABB has some good info on its website.

 

[stevenal]

Some designs work to clear arcing faults more quickly. These would affect the boundary and PPE by NFPA. Other designs don't appear to be covered.

 

[Brimy]

Zogzog - If the switchgear is arc-resistant and the doors are closed, can I assume that the arc flash hazard is eliminated and PPE is not required. For example: from table 130.7(C)(9)(a)of 70E, CB or fused switch operation > 1kV with doors closed requires a PPE level 2. Does arc-resistant gear negate this hazard?

I guess I would like to have this blessing come from NFPA rather than the generalities given by the switchgear manufacturers.

 

[dpc]

Yes, if you have arc-resistant switchgear AND the doors are closed, PPE is not required.

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.

 

[Brimy]

Following reply is from are-resistant switchgear manufacturer: "Since arc resistant switchgear (not only ABB's but any manufacturer's) is intended to control the explosion from an arc event, and not to reduce the amount of incident energy, the standards do not state that the level of PPE can be reduced. It still is up to the user to define the level of PPE."

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.

 

[safetydan]

70E 130.7(C)(1) states that: When an employee is working within the Flash Protection Boundry he/she shall wear protective clothing and other personal protective equipment in accordance with 130.3.

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.

 

[Zogzog]

If the switchgear is ANSI-rated and tested for arc-resistance then you have removed the hazard. So why increase the risk of an accident by wearing PPE you dont need? Personally, I think OSHA would lose that battle in court.

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.

 

[Brimy]

The response from NFPA is that 70E does not address arc-resistant switchgear, and as such, there is no reduction in PPE requirements with the use of arc-resistant gear.

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.

 

[davidbeach]

Arc-resistant switchgear is ONLY arc-resistant with the doors closed and all bolts/latches in place. If you have the door open it is just switchgear.

 

[stevenal]

But is PPE required with even non-arc-resistant switchgear when doors are closed? NFPA 70E section 130 (where the PPE requirements are) is titled "working on or near live parts." Standing next to switchgear with latched/bolted doors doesn't seem to count. And what PPE is going to prevent injury when the door is blasted in your direction?

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.

 

[dpc]

The absence of permission in NFPA 70E does not constitute a requirement.

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.

 

[Brimy]

The NFPA 70E only requres a level 0 PPE around metal clad switchgear (with doors closed).

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!

 

[Brimy]

I should clarify my last post. Operate a circuit breaker or fused switch in >1kV metal clad switchgear and the PPE recommendation jumps to level 2.

 

[dpc]

Briny,

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

 

[Brimy]

Well now I am confused (again). Since the calculation does not take into consideration that the switchgear doors are closed or open, do I consider all tasks as if they are performed on energized and exposed equipment?

This would mean that the switchgear could not even be approached without PPE level 4 - regardless of task!

Thanks dave, I appreciate the discussion.

 

[Zogzog]

I discussed this with some guys on the 70E commitee last weeek at the NETA conference and they pointed out that you have to factor in risk. What is the risk when standing in front of a switchgear lineup when you are not doing anything? The answer is little or no risk, but standing in the same place when you are racking out a circuit breaker is a higher risk.

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).

 

[dpc]

That's the question, isn't it. NFPA-70E seems contradictory in this area.

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.