NFPA 70E, Opening of doors is an arc flash risk?

[skeet67]

I am trying to get some opinions on the arc flash hazard identification from Table 130.7(C)(15)(A)(a) in the 2015 NFPA 70E
The task I am most interested in is: Opening voltage transformer or control power transformer compartments.
Almost everywhere on our system I consider opening a door not an action that can cause an arc flash. As soon as someone crosses the plane of the door then I will say they need to have the proper PPE. I do work for a utility so the 70E standard does not apply for most of my work.

In this case the 70E standard does apply.
The equipment in question is a 24kV/480V pad mount transformer 1000kva, no exposed conductor on the 24kV side, exposed connection pad on the 480V side where the cables bolt to.
When I look at the risk register for this it seems very unlikely that an arc flash could occur.

What has your position been on this?

If I look at this scenario and determine the risk is low do I have to wear PPE specifically for opening the cabinet door?

Thanks for your input,

 

[krisys]

Opening door is certainly has an arc flash hazard.

 

[dpc]

Agreed. NFPA 70E-2015 clearly indicates that opening a door to expose live parts requires appropriate PPE. In my opinion, pad-mounted transformer terminal compartments are fairly high risk to open while energized, especially since the LV side must be opened first before the HV side can be opened.

 

[wbd]

I am trying to get some opinions on the arc flash hazard identification from Table 130.7(C)(15)(A)(a) in the 2015 NFPA 70E
The task I am most interested in is: Opening voltage transformer or control power transformer compartments.

I don't think opinions really matter as NFPA 70E is very clear on the requirement for Arc Flash PPE when opening up covers. There have been arc flash events during opening covers and that is why the requirement is there.

 

[jraef]

As I see it, you are falsely interpreting the act of opening the door as creating a risk of an arc flash. In fact, the risk is already there because there are live components inside of the shared air space, and if an arc flash happens anywhere within that shared space, the effects are transmitted throughout it; the extreme pressure wave, the heat blast, even the plasma ball are not stopped by having to go around corners or though wire way openings etc. So really, opening the door merely exposes one to that risk.


"You measure the size of the accomplishment by the obstacles you had to overcome to reach your goals" -- Booker T. Washington

 

[ScottyUK]

OTOH, the very act of disturbing the equipment is often the act which provokes a fault to occur even if it might sit there benignly if left undisturbed.

Over here we aren't governed by NFPA 70E but we take an interest in it because there isn't an equivalent IEC or EN standard, plus we're American-owned and head office do take some interest in what we do. I agree with the guys above: the only question is whether can you lower the flash hazard sufficiently to be able use PPE at all. Unless you have some sort of unit scheme - which is unusual on a small transformer - the only protection which will help you is the HV overcurrent element and that will be relatively slow to respond to an LV arcing fault.

FWIW, the heaviest arc-flash PPE we can get is 100 cal/cm². The manufacturer's sales guy described it as being 'a bag to hold all the bits together when you go through the switch-house wall'. It's comforting to know that.

 

[davidbeach]

Maintenance mode protection on the high side, set to trip instantaneously for low side faults can provide a significant reduction flash energy. I've heard the higher level arc flash suits as providing the difference between an open casket funeral and a closed casket funeral. If there are ever to be higher energy arc flash suits they will have to be fully rigid as the pressure impulse will be lethal even before the skin begins to warm up.

 

[Zogzog]

Just looking at risk you have to ask why are you opening the door? If you are investigating a proplem, like maybe the transformer is singled phased there is a good chance there is a broken bushing or something in that LV side and when you open the door a very high risk of disturbing the cables. Giong in there for IR scanning maybe not so much. Taking an oil sample, usually you have to get pretty close and move the cables around a bit to get to the sample valve.

 

[jimmy2times]

I've heard of an incident whereby a loose cover was dropped on busbar during a thermographic survey. person involved was air lifted from the ship to shore for treatment. agree with Scotty Re: the act of distrubing; the likliehood is high on a ship where vibration could effect securings/fittings of latches, hinges, covers etc.