Opening live panelboards

Schwinn krate

Member
Location
Nyc
Occupation
Electrician
Have a switch gear 120v 208 2000 amp switchgear. Want to know if I need ppe when opening panel covers when circuit is live. Fed by 125 kva transformer.
 

Buck Parrish

Senior Member
Location
NC & IN
I'm going to out on a limb here and say yes.

from www.osha.gov
1910.335(a)
Use of protective equipment.
1910.335(a)(1)
Personal protective equipment.
1910.335(a)(1)(i)
Employees working in areas where there are potential electrical hazards shall be provided with, and shall use, electrical protective equipment that is appropriate for the specific parts of the body to be protected and for the work to be performed.

Note: Personal protective equipment requirements are contained in subpart I of this part.
1910.335(a)(1)(ii)
Protective equipment shall be maintained in a safe, reliable condition and shall be periodically inspected or tested, as required by 1910.137.
1910.335(a)(1)(iii)
If the insulating capability of protective equipment may be subject to damage during use, the insulating material shall be protected. (For example, an outer covering of leather is sometimes used for the protection of rubber insulating material.)
1910.335(a)(1)(iv)
Employees shall wear nonconductive head protection wherever there is a danger of head injury from electric shock or burns due to contact with exposed energized parts.
1910.335(a)(1)(v)
Employees shall wear protective equipment for the eyes or face wherever there is danger of injury to the eyes or face from electric arcs or flashes or from flying objects resulting from electrical explosion.
1910.335(a)(2)
General protective equipment and tools.
1910.335(a)(2)(i)
When working near exposed energized conductors or circuit parts, each employee shall use insulated tools or handling equipment if the tools or handling equipment might make contact with such conductors or parts. If the insulating capability of insulated tools or handling equipment is subject to damage, the insulating material shall be protected.
1910.335(a)(2)(i)(A)
Fuse handling equipment, insulated for the circuit voltage, shall be used to remove or install fuses when the fuse terminals are energized.
1910.335(a)(2)(i)(B)
Ropes and handlines used near exposed energized parts shall be nonconductive.
1910.335(a)(2)(ii)
Protective shields, protective barriers, or insulating materials shall be used to protect each employee from shock, burns, or other electrically related injuries while that employee is working near exposed energized parts which might be accidentally contacted or where dangerous electric heating or arcing might occur. When normally enclosed live parts are exposed for maintenance or repair, they shall be guarded to protect unqualified persons from contact with the live parts.
1910.335(b)
Alerting techniques. The following alerting techniques shall be used to warn and protect employees from hazards which could cause injury due to electric shock, burns, or failure of electric equipment parts:
1910.335(b)(1)
Safety signs and tags. Safety signs, safety symbols, or accident prevention tags shall be used where necessary to warn employees about electrical hazards which may endanger them, as required by 1910.145.
1910.335(b)(2)
Barricades. Barricades shall be used in conjunction with safety signs where it is necessary to prevent or limit employee access to work areas exposing employees to uninsulated energized conductors or circuit parts. Conductive barricades may not be used where they might cause an electrical contact hazard.
1910.335(b)(3)
Attendants. If signs and barricades do not provide sufficient warning and protection from electrical hazards, an attendant shall be stationed to warn and protect employees.
 

mayanees

Senior Member
Location
Westminster, MD
Occupation
Electrical Engineer and Master Electrician
Yes. It's rationalized using 70E Table 130.5(C) Estimate of the Likelihood of Occurrence of an Arc Flash Incident, for the task of opening hinged or bolted covers it's listed as a Yes so PPE must be worn. An IR guy wouldn't need to wear PPE as long as the restricted approach boundary wasn't crossed (12 inches).
 

don_resqcapt19

Moderator
Staff member
Location
Illinois
Occupation
retired electrician
How does a 125kva transformer supply 2000 amp switchgear? Typically the highest incident energies will be on the line side of the first overcurrent protective device for the secondary of the transformer.
 

mayanees

Senior Member
Location
Westminster, MD
Occupation
Electrical Engineer and Master Electrician
How does a 125kva transformer supply 2000 amp switchgear? Typically the highest incident energies will be on the line side of the first overcurrent protective device for the secondary of the transformer.
When it's owned by the Utility?
The difficulty comes in determining the appropriate PPE. If it is in fact the service-entrance off the secondary of a 3-phase, 125 kVA transformer then one couldn't use the PPE Categories method 130.7(C)(15) in 70E because that assumes there's an upstream ocpd. It should work for the fault current limitations imposed by Table 130.7(C)(15)(a) since the fault current will be 125,000/208/1.732 = 347 amps divided by the transformer's nameplate impedance. If it's as low as 2% there's only 347/.02 = 17,350 amps using the infinite bus fault current calculation, which is less than the 25kA limiter in the table. But again this assumes there's an upstream ocpd.
I would request details about the service-entrance, like primary ocpd and Utility contribution numbers and model it in SKM for determination of incident energy and then suit up accordingly.
I question whether the situation is real because 125 kVA is not a typical size and could be referring to the old 125 kVA exemption from a couple code cycles back. That limitation has been reduced in IEEE 1584 to 2000 amps of bolted fault current, which is closer to around 25 kVA.
 
Last edited:

mayanees

Senior Member
Location
Westminster, MD
Occupation
Electrical Engineer and Master Electrician
When it's owned by the Utility?
The difficulty comes in determining the appropriate PPE. If it is in fact the service-entrance off the secondary of a 3-phase, 125 kVA transformer then one couldn't use the PPE Categories method 130.7(C)(15) in 70E because that assumes there's an upstream ocpd. It should work for the fault current limitations imposed by Table 130.7(C)(15)(a) since the fault current will be 125,000/208/1.732 = 347 amps divided by the transformer's nameplate impedance. If it's as low as 2% there's only 347/.02 = 17,350 amps using the infinite bus fault current calculation, which is less than the 25kA limiter in the table. But again this assumes there's an upstream ocpd.
I would request details about the service-entrance, like primary ocpd and Utility contribution numbers and model it in SKM for determination of incident energy and then suit up accordingly.
I question whether the situation is real because 125 kVA is not a typical size and could be referring to the old 125 kVA exemption from a couple code cycles back. That limitation has been reduced in IEEE 1584 to 2000 amps of bolted fault current, which is closer to around 25 kVA.
To close the loop on this for my own good... I do 70E compliance electrical safety classes and have done this for hundreds of participants over the past 5 years. I always offer that my email address is listed in the handout material, and if I can ever provide you with an incident energy level for PPE usage, just email me and I'm happy to do it. So given that premise, if I was asked what PPE to wear to access the secondary of a 125 kVA 208V transformer, I'd say 20 calories. I used a 13,200 Volt, 75 MVA strength source, and a 150 kVA transformer with standard impedance, and a 2-second timeout of any overcurrent protection, line or load side, I came up with 18.3 calories. I've seen 300 kVA transformers in PDUs in Data Centers with 40 calorie secondaries, 130 calorie secondaries of 2000 kVA transformers and everything in between. So based on that I think a 20 calorie PPE suit would suffice. Sure, wear a 40 if you have it, and if you don't need to do much with mobility, and if it's cool enough, but a 20 cal suit should suffice.
 

Schwinn krate

Member
Location
Nyc
Occupation
Electrician
To close the loop on this for my own good... I do 70E compliance electrical safety classes and have done this for hundreds of participants over the past 5 years. I always offer that my email address is listed in the handout material, and if I can ever provide you with an incident energy level for PPE usage, just email me and I'm happy to do it. So given that premise, if I was asked what PPE to wear to access the secondary of a 125 kVA 208V transformer, I'd say 20 calories. I used a 13,200 Volt, 75 MVA strength source, and a 150 kVA transformer with standard impedance, and a 2-second timeout of any overcurrent protection, line or load side, I came up with 18.3 calories. I've seen 300 kVA transformers in PDUs in Data Centers with 40 calorie secondaries, 130 calorie secondaries of 2000 kVA transformers and everything in between. So based on that I think a 20 calorie PPE suit would suffice. Sure, wear a 40 if you have it, and if you don't need to do much with mobility, and if it's cool enough, but a 20 cal suit should suffice.
Thank you much appreciate
 

Schwinn krate

Member
Location
Nyc
Occupation
Electrician
When it's owned by the Utility?
The difficulty comes in determining the appropriate PPE. If it is in fact the service-entrance off the secondary of a 3-phase, 125 kVA transformer then one couldn't use the PPE Categories method 130.7(C)(15) in 70E because that assumes there's an upstream ocpd. It should work for the fault current limitations imposed by Table 130.7(C)(15)(a) since the fault current will be 125,000/208/1.732 = 347 amps divided by the transformer's nameplate impedance. If it's as low as 2% there's only 347/.02 = 17,350 amps using the infinite bus fault current calculation, which is less than the 25kA limiter in the table. But again this assumes there's an upstream ocpd.
I would request details about the service-entrance, like primary ocpd and Utility contribution numbers and model it in SKM for determination of incident energy and then suit up accordingly.
I question whether the situation is real because 125 kVA is not a typical size and could be referring to the old 125 kVA exemption from a couple code cycles back. That limitation has been reduced in IEEE 1584 to 2000 amps of bolted fault current, which is closer to around 25 kVA.
Not utility. This comes from customers side. 4160 coming in to step down to 120 208.
 

romex jockey

Senior Member
Location
Vermont
The Canadian model panels completely enclose service ent conductors , that our 408.3 (2) was going to follow suit a few cycles ago was exciting news. Only to find these international manufacturers cheesing it out in American markets , with corny little terminal covers.
1630835098413.png
~RJ~
 

infinity

Moderator
Staff member
Location
New Jersey
Occupation
Journeyman Electrician
The Canadian model panels completely enclose service ent conductors , that our 408.3 (2) was going to follow suit a few cycles ago was exciting news. Only to find these international manufacturers cheesing it out in American markets , with corny little terminal covers.
View attachment 2557745
~RJ~
What is the real benefit of this? Our line side terminals are already required to be protected so I see no benefit to following the things they do in Canada. That photo looks pretty dumb not coming into the top of the panel.
 

romex jockey

Senior Member
Location
Vermont
What is the real benefit of this?
the trade's safety , us , you, me & every other spark reading here ...

via the very same manufacturers that foist 'safety related' products and their subsequent updates upon the CMP's

70E could stay in the truck, along with the 12-20 cal suit & the osha man if we 'rated' the same as our northern counterparts

~RJ~
 

infinity

Moderator
Staff member
Location
New Jersey
Occupation
Journeyman Electrician
the trade's safety , us , you, me & every other spark reading here ...

via the very same manufacturers that foist 'safety related' products and their subsequent updates upon the CMP's

70E could stay in the truck, along with the 12-20 cal suit & the osha man if we 'rated' the same as our northern counterparts

~RJ~
How is really more safe? The terminals on the main are now required to be insulated so when the main CB is off there are no exposed live parts. For that reason I see no purpose for what is shown in the photo.
 

Fred B

Senior Member
Location
Upstate, NY
Occupation
Electrician
How is really more safe? The terminals on the main are now required to be insulated so when the main CB is off there are no exposed live parts. For that reason I see no purpose for what is shown in the photo.
well, apparently the Canadians do Infinity

~RJ~
The way it is done in the states here you still technically have a live panel even with breaker off (OSHA standards). The Canadian method of isolating the service conductors makes it no longer a live panel with breaker off, no access to live conductors while working on branch circuits.
 

romex jockey

Senior Member
Location
Vermont
The way it is done in the states here you still technically have a live panel even with breaker off (OSHA standards). The Canadian method of isolating the service conductors makes it no longer a live panel with breaker off, no access to live conductors while working on branch circuits.
bingo!
~RJ~
 

Jraef

Moderator
Staff member
Location
San Francisco Bay Area, CA, USA
Occupation
Electrical Engineer
Have a switch gear 120v 208 2000 amp switchgear. Want to know if I need ppe when opening panel covers when circuit is live. Fed by 125 kva transformer.
Those two data points don't match. Sure, it is POSSIBLE to over size your switchgear by 300% or so, but really?

You need PPE to open ANY switchgear that is live, the only issue is at what level.

You also need a Live Work Permit from whomever is in charge of safety for the organization you work for, because THEY need a Safe Electrical Work Practices program that would make SURE that you know all of this before you ever open or even think about opening a panel. The fact that you are asking means whomever you are doing this for is in violation of OSHA workplace requirements and if something bad happens, they can be held CRIMINALLY responsible. Ignorance is NOT an excuse either. You tell them that...
 

infinity

Moderator
Staff member
Location
New Jersey
Occupation
Journeyman Electrician
You need PPE to open ANY switchgear that is live, the only issue is at what level.

You also need a Live Work Permit from whomever is in charge of safety for the organization you work for, because THEY need a Safe Electrical Work Practices program that would make SURE that you know all of this before you ever open or even think about opening a panel. The fact that you are asking means whomever you are doing this for is in violation of OSHA workplace requirements and if something bad happens, they can be held CRIMINALLY responsible. Ignorance is NOT an excuse either. You tell them that...
I read things like this often but where I work we do not follow NFPA70E nor do we have live work permits. And no one is using PPE to open a panel cover. If safety Sam walks by when you're working inside of a live panel all he cares about is your hard hat being on your head.
 

mayanees

Senior Member
Location
Westminster, MD
Occupation
Electrical Engineer and Master Electrician
Those two data points don't match. Sure, it is POSSIBLE to over size your switchgear by 300% or so, but really?

You need PPE to open ANY switchgear that is live, the only issue is at what level.

You also need a Live Work Permit from whomever is in charge of safety for the organization you work for, because THEY need a Safe Electrical Work Practices program that would make SURE that you know all of this before you ever open or even think about opening a panel. The fact that you are asking means whomever you are doing this for is in violation of OSHA workplace requirements and if something bad happens, they can be held CRIMINALLY responsible. Ignorance is NOT an excuse either. You tell them that...
With all due respect Jraef, guru of all things motor/VFD related, The Energized Electrical Work Permit (EEWP) is not required if opening for inspection, but one must be suited to the correct PPE level.

130.2 (A) When Required.
When work is performed as permitted in accordance with 110.4, an energized electrical work permit shall be required and documented under any of the following conditions:
  • (1) When work is performed within the restricted approach boundary
  • (2) When the employee interacts with the equipment when conductors or circuit parts are not exposed but an increased likelihood of injury from an exposure to an arc flash hazard exists
I use table 130.5(C) Opening hinged door(s) or cover(s) or removal of bolted covers (to expose bare, energized electrical conductors and circuit parts). Equipment in Any condition, likelihood of occurrence of an arc flash is Yes, so PPE must be worn.

I recently took an NFPA-sponsored virtual live class and left with the understanding that when we do data collection for Arc Flash Studies we are okay to open panels and covers for documentation of the system without an EEWP as long as I'm suited to the incident energy level. But we can no longer install recording CTs in panels or on transformer secondary conductors without an EEWP.
 
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