Back to Basics question - what's the right arc flash PPE in this case?

[tankfarms]

So recently I noticed an electrician switching on/off a 480V MCC main breaker for maintenance. The arc flash label on the breaker panel is marked 60 cal. I told him it's best to get a flash suit on for the following two reasons
1. Main breakers like this haven't been exercised for a long time, we don't know its condition
2. Arc flash cal. is high in this case, and the 480V panels are NON arc blast resistant, and I told him if there was a fault, it wouldn't make a difference if you had that panel in front of you or not.

His argument of not wearing the flash suit:
I only need the flash suit if I rack the breaker in/out, since there's no racking in/out action, I don't need the flash suit.

So, what's the correct action in this case? Any particular place on the NFPA 70E we can look to seek some clarifications?

Thanks.

 

[petersonra]

I don't think there is an arc flash suit rated for 60.

So either you have to convince yourself no arc flash protection is required or you get a motor operator and stand a long ways away.

 

[mayanees]

He needed to use a remote operator!
60 calories makes it HRC Dangerous, such that no safe PPE exists to interact with the equipment.
The cutoff is 40 calories.
And you can't use the 70E 130.7(C)(15)(a) tables, because it's already labelled.
HOWEVER!!!
If the facility has an Electrical Safety Program that has determined that operating MCC controls is acceptable based on their Risk Assessment, (which is a defensible position perhaps based on the 2012 70E info note that states equipment is not subject to arc flash when operated as intended) then he would be okay to operate it. It's not likely that's been done, especially since it's HRC Dangerous.
John M

 

[zog]

2012 70E info note that states equipment is not subject to arc flash when operated as intended

That isn't exactly what it says.


Arc Flash Hazard. A dangerous condition associated with the possible release of energy caused by an electric arc.

Informational Note No. 1: An arc flash hazard may exist when energized electrical conductors or circuit parts are exposed or when they are within equipment in a guarded or enclosed condition, provided a person is interacting with the equipment in such a manner that could cause an electric arc. Under normal operating conditions, enclosed energized equipment that has been properly installed and maintained is not likely to pose an arc flash hazard.

Informational Note No. 2: See Table 130.8(C)(15)(1) for examples of activities that could pose an arc flash hazard.


IN Note 1 is refering to a normal (Steady state) condition, this is intended to clarify PPE is not required to simply walk past the equipment that is energized. It says there IS a risk an arc flash could occur but the probibility of that is low enough to not require PPE

IN Note 2 clarifies tasks listed in the task tables are example of activities that could pose a hazard, operating a breaker is one of the listed items.

I know some people will argue how I am reading this but this was a hot topic at NETA/Powertest last week and one of the 70E commitee members gave a presentation discussing this exact thing and this is how it was meant to read, ROP's for more concise verbage is already in the works for the next cycle.

 

[zog]

Get a remote operator and remote racking, or mitigate the Ei to <40cal/cm2. Those are the options.

 

[GoldDigger]

enclosed energized equipment that has been properly installed and maintained...

That part of it probably has not been demonstrated either based on the OP's description.

 

[zog]

That part of it probably has not been demonstrated either based on the OP's description.

Well that is a whole different debate. What does that mean? The OEM's recommend complete refirbishments of ANSI breakers every 250-2000 operations (Depends on the breaker), is that "peoperly maintained"? Nuclear plants and Google would say yes, many other places never do.

How do you even know your entire arc flash safety program is even legit? Arc flash labels and the PPE requirements are all based off an assumption they trip when the TCC's say they should. Typical trip tests can't verify that because you need to open and remove a breaker to test it and doing that act breaks free dried grease, gummed up mechs, dirt, etc... How long will it really take that breaker to trip when it has been sitting there closed for months or years? If you assumed a 5 cycle clearing time and it really would take 10 cycles that doubles the arc flash hazard and could easily exceed the ratings of the PPE being used.

 

[zog]

Tankfarm, what type of breaker is it?

 

[tankfarms]

Tankfarm, what type of breaker is it?

Thanks Zog, for your feedback. This is a 1200A molded case CB with trip unit. I don't know the exact brand/model as I haven't opened the panel door yet.

Please note, that you mentioned to use "remote operator" to "rack in/out". I want to mention that we are only talking about normal operation (manually switch CB on/off) with panel door closed in this case. However, because of the hi arc flash energy, it started the topic thus discussion here.

 

[GoldDigger]

Thanks Zog, for your feedback. This is a 1200A molded case CB with trip unit. I don't know the exact brand/model as I haven't opened the panel door yet.

Please note, that you mentioned to use "remote operator" to "rack in/out". I want to mention that we are only talking about normal operation (manually switch CB on/off) with panel door closed in this case. However, because of the hi arc flash energy, it started the topic thus discussion here.

The mention of remote operator applied to two different things: A remote operator for simple manual operation and a remote actuator for racking. The latter would only be needed or helpful if there were ever a need to rack it in or out while the feed was live. And in that case it would be mandatory because of the hazard level indicated.
Based on the information presented in this thread so far, I think the consensus is that remote actuation is also the only safe way to manually operate the breaker while it is still energized, unless the rating can be changed.