Electric Panel & Disconnect Switch-Arc Flash PPE 2

[Ishrit]

Hi All,

I did some research on this site looking some basic answers but could not get to the bottom of my dilemma.

In case of a 600V/480 V fused disconnect switch or an electric panel(240 V fed from 150 kVA TXF), if we have to just operate these equipment while these are encased and similar goes to a 600 V switchgear, Is it mandatory by NEC, CSA Z462, NFPA or recommended to wear proper PPE while operating this equipment.
I am sure a lot you guys look in to the electrical safety program in your facilities everyday. I am in consulting buisness and dont get to see a site everyday.

For example, a lighting panel in a office hallway, if it has a cat 3 energy, Is it ok for some body to operate it without a PPE may be for a Janitor.

I would appreciate an opinion.
Thanks

 

[Zogzog]

The 2009 70E clarified this, any interaction with the equipment, covers on or off, require the operator (Regardless of his or her job description) to wear the proper PPE. The person operating the equipment needs to be qualified per the 70E definition, that can be a task specific qualification if the janitor needs to operate this switch only.

It sounds like you (they) are using the tables, an actual Ei from an analysis may show a much lower hazard.

 

[Ishrit]

Thanks ZogZog. I have a situation where a switchgear is 600 v and has a 750 kVA dry type transformer and fed from a circuit breaker located far away. The switchgear has a non fused disconnect switch before primary.

It has a Cat3 .energy level. The suggestion is to install a current limiting fuse disconnect switch in parallel with the existing switch. So when a repair needs to be done
on the switchgear, the fused switch will be closed and the non-fused switch will be opened. So that while repair is being done the arc energy is less due to the fused switch.

What I am wondering is that; some body who will operate that non fused switch , Does he need to wear a PPE because that switch has a cat 3 arc level as well. If yes than there is no point in having this fused switch?

I would appreciate a word.
Thanks

 

[Zogzog]

You nned to do an arc flash study to see if you are gaining anything here, current limiting fuses only limit current in thier current limiting range so at low fault currents it may not help at all, often the lower fault currents and resulting long clearing times are your largest hazard.

Chances are there are better solutions. But to answer your question, the same hazard would exist for operating the fused and non-fused switch because it is the fault current coming to the switch and the clearing time of the upstream breaker that determne the hazard level.

 

[jraef]

But are you referring to operating these devices with the doors open or closed? It makes a big difference. Even if the equipment ends up as Cat 3, with the door closed it may be Cat 0 and most switchboards can be operated from the outside without opening a door. Same for panel boards. The Arc Flash issue is geared towards maintenance people who might be servicing equipment and components INSIDE of the switchboard or panel boards. I would not imagine you want a janitor doing that no mater what!


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[Zogzog]

jraef, I disagree, sort of. I know in real life there is a difference between doors open and closed, and when using the tables there is a difference. But when an arc flash analysis is done there is no difference, the doors have to be assumed to fail, unless the equipment is arc rated.

 

[dpc]

NFPA 70E is not consistent on this. If a study is done, then Zogzog is correct, at least in my interpretation.

But if you are using the Table in NFPA 70E in lieu of doing a study, then there is a difference because the table is task-based, rather than hazard-based.

This is big inconsistency in NFPA 70E that creates a lot of confusion.

We all feel safer with the doors closed or covers on, and instinctively we know it is safer, but it is always good to remember that there is no testing done to determine how much safer. If there is enough incident energy released, the doors and covers can be blown off, unless the gear is arc-rated as Zog says.

We generally revert to the NFPA table for 120/240 V panels just because there is no other approach that makes any sense.



"The more the universe seems comprehensible, the more it also seems pointless." -- Steven Weinberg

 

[Zogzog]

Totally agree with DPC's post. Remmember the tables are not based on any actual data but a "gut feeling" of the 70E commitee, hence the reduced HRC's for some tasks and equipment with covers on.

 

[Ishrit]

Thanks all.
So that means installing a fused switch in parallel with the non fused switch is ok and when ever a repair needs to be done on switchgear with doors open, the fused switch will be closed and non fused switch will be open.

Based on the current Arc flash analysis, I put a bus to simulate the energy level at the switch, the energy level is 3, So I should presume that it should not matter because all these switches have doors and can be operated without worrying about being blown off?

If arc flash is not a concern with doors closed, why we need remote racking device for breakers.
Iwould appreciate a word.

 

[dpc]

Who said arc-flash was not a concern if doors are closed?

I think you are mis-reading the comments made.

I'd suggest maybe hiring someone qualified to do an arc-flash hazard analysis.







"The more the universe seems comprehensible, the more it also seems pointless." -- Steven Weinberg

 

[Zogzog]

You are totally misunderstanding us.

First and foremost, you cant work on switchgear energized unless you have a justifiable reason to do the work energized.

Second, to operate the switches you are discussing (Fused or unfused) there is an arc flash hazard and you will need PPE.

Third, "energy level 3" makes no sense at all, you dont seem to be grasping the doors open/closed concept, the doors dont protect you, at least you have to assume they wont.

TPlease follow dpc's advice and hire a qualified engineering firm to do your analysis for you, or get the right training. We are glad to help but cant do it all for you.