Arc Flash disagreement 1

[Eleceng01]

I am having a disagreement on NFPA70E and IEEE1584-2002 with a collegaue. He believes that arc flash boundaries apply AT ALL times (i.e. no maintenance, inspection, or electrical work). I believe that the arc flash requirements only apply while performing 'live' electrical work.

Can I please get your opinion - have I missed something in the literature or my understanding?

 

[Zogzog]

This was discussed at the NETA conference in Denver last month with a panel of 70E commitee members. The consensus was that the boundaries apply when you are interacting with the equipment. Not necessarily when persorming live work but opening doors, operating switches or circuit breakers, etc.

However it was also noted that an arc flash can occur at any time (Animals, water, insulation failure) so you can be exposed to an arc flash if you are in the boundary doing nothing, but the term "Interacting with the equipment" was stressed.

 

[Eleceng01]

Zogzog, thanks. From your post it sounds like the NETA 70E committee members agree with me. Yes, I forgot to mention other 'interactions'.

 

[dpc]

Agree with zogzog. If you are just "passing through" and there are no exposed live parts, no special PPE is required. If you're opening doors, racking breakers, etc, then arc-flash hazard must be considered.

This is somewhat vague in NFPA 70E, probably intentionally.

 

[Zogzog]

I believe there was a proposal being reviewed by the commitee to add text to clarify this.

 

[stevenal]

Kinda academic to discuss when a boundary exists. Is it still a boundary when it doesn't apply to me? Hardy notice those fences when I'm out driving my tank. The real question is: where, when, and what level PPE is required. Already answered in the standard.

 

[Breakerboy]

The comments about passing by the bus with no interaction seems to make sense until you have a fault on a 13.8kv bus that blows the 170lb door off of the hinges, breaks the latches and the door stop and throws the door 25 feet into another bus. We had that happen 23 years ago and now we maintain the area roped off with red and black danger flaging and signs requireing Control Room permission to access the area. It is true that the arc flash boundary doesn't come into play unless there is "interaction". We prohibit acces to those areas unless we must interact with the equipment.

 

[Zogzog]

Well you could be golfing and lightning could strike nearby, so do we need PPE to golf? No, the probalibity factor comes into play here, I agree with you switchgear can fail without interaction for many reasons, we get emergency service calls quite often, but requiring PPE all of the time is just not practicle. Your policy makes sense for a 13.8kV substation room, but consider a 480V MCC on a production floor that people walk near all day long.

 

[Breakerboy]

I agree that 480v MCC's do not need flagged off nor do we need PPE to be in the area. We roped off our 13.8kv switchgear rated at 76.5 cal/cm2. We have considered roping off the 4.16kv switchgear as well since they are all in the mid 30's of cal/cm2. The need for anyone to casually walk in these areas is minimal. The whole idea of how to protect our employees comes in when they are performing work on those high energy busses. We should not put them at risk. The real problem besides the danger of the arc flash blast, is that we have not done a good job of getting the experience out to each other when something goes wrong. This stuff is happening every day and we only hear about a fraction of the incidents.

 

[rbulsara]

One more time:

All the discussion of PPE when you are not working live on electrical equipment are meaningless.

PPE offer "reasonable" protection only for "burn" injuriesfrom a arc flash blast. That too only to limit to a second degree which is most painful. PPE are not even intended to offer protection against flying debris or objects. So while boundaries may exist, PPE is only required or useful when interacting with "open" live equipment.

The type of risks that exist or injury that can occur when the gear is enclosed and blast occurs inside and one happens to be just walking by the gear, CANNOT be reduced by a PPE nor PPE are designed for it.

So all the discussion of PPE when you are not working live on it are meaningless.

 

[wbd]

Just to clarify:

1. PPE is required for interacting with the subject eqpt. This interaction could include operating breakers.

2. PPE is not required when walking by or standing by exposed eqpt even though it is within the arc flash boundary.

I have seen a situation in an old power plant that has open 480V, delta, copper bus bars for the bus with breakers directly bolted to the bus work with cable on the other side. These breakers are just behind a mesh screen with the bottom 3 ft completely open and all the bus work open about 10 feet off the ground. The plant operator has to stand with his back to this, about 6 feet away to synch and close in the generators attached to the bus.

The fault current on these buses is around 37 - 51kA, depending on generation. This put the AFH from Cat 3 to extreme hazard.

 

[stevenal]

Further clarification is needed.

1. PPE is required when anyone is interacting with the subject equipment.

2. PPE is not required when walking by or standing by exposed eqpt even though it is within the arc flash boundary; unless someone else is interacting with the equipment.

It is not enough that the guy performing the task wear the PPE; everyone else needs to suit up or leave the boundary area.

 

[don01]

hi all
I live under a different set of rules awhere limits of approach are set for all access to area. So this conversation is acedemic to that but lets take a step back - You & I have a duty of care to all in our charge & those around us.
If we dont have enough ppe for the tourists then they walk away. It is really hard to rebuild people & there is only one recorded case of resurection (and half the world doubts that).
SO I would (and probably am) known for being cautious and I suggest that life style to all playing with HV or looking to "save a bit".

Anyway enjoy the journey & grab the memories
Don