PPE - Operating Breakers and Bolt-Loc Switches ?

Davebones

Senior Member
We have 4 main 480 services coming into our plant . These range from 4000 amp to 1600 amp . We have bolt-loc switches and molded case SQ D circuit breakers on them . They all have Incident energy level of ( 173 cal/cm at working distance of 1 ft 6 in ) . The PPE level - site-specific says " PROHIBITED " . ( Arc Flash Boundary is 31 ft 2 in ) . I use the PPE we have which is rated 25 Cal's when opening or closing a breaker or switch . Is PPE required to operate a breaker or switch ? If it says "PROHIBITED " is this saying that we must use a remote switch actuator ?
 

jim dungar

Moderator
Staff member
We have 4 main 480 services coming into our plant . These range from 4000 amp to 1600 amp . We have bolt-loc switches and molded case SQ D circuit breakers on them . They all have Incident energy level of ( 173 cal/cm at working distance of 1 ft 6 in ) . The PPE level - site-specific says " PROHIBITED " . ( Arc Flash Boundary is 31 ft 2 in ) . I use the PPE we have which is rated 25 Cal's when opening or closing a breaker or switch . Is PPE required to operate a breaker or switch ? If it says "PROHIBITED " is this saying that we must use a remote switch actuator ?
The term Prohibited is not in NFPA70E. Many, if not most, companies have chosen to prohibit 'work' on equipment >40 cal/cm^2, per their Electrical Safe Work Practices program.

Before I go any further.

How often have your bolted pressure switches been operated, daily, yearly, never?
How often are your switches been maintained, cleaned and lubricated? I think manufacturers recommend every 5 yrs.
 

mayanees

Senior Member
Normal Condition

Normal Condition

Davebones,
As long as the equipment is in normal condition it can be operated without PPE based on table 130.5(C).
The Normal definition includes properly maintained, which is where much equipment falls short of being Normal. Most electrical testing companies that I've dealt with put a dated sticker on the gear after performing maintenance.
 

Jraef

Moderator
Staff member
The incident energy levels and approach boundaries apply to EXPOSED conductive elements. Operating with the doors closed, although still risky for equipment that is NOT rated as Arc Resistant (but properly maintained as mentioned above), should not be assigned the same risk level. What you are seeing is likely a “lazy man’s” risk assessment technique. CYA by forbidding any interaction.

In my opinion this attitude is actually leading to MORE risk because people tend to ignore equipment they are afraid to use. As someone put it to me yesterday when discussing this, “Our switchgear is basically a fuse now. We can’t go near it, we can’t shut it down or test it, so the only time we can inspect, maintain or repair it is after something blows up.”
 

Davebones

Senior Member
We've had the switchgear cleaned and tested roughly every 5 years on . It's in a air conditioned environment . I understood that as long as you have maintained it you ( 70E ) said you can operate it . I choose to use the PPE as a extra precaution . I asked the question as with some of the previous posts I've seen it can get confusing about PPE and operating a switch or a breaker . The sticker " PROHIBITED " was put on it after we had the arc flash study done .
 

zog

Senior Member
We've had the switchgear cleaned and tested roughly every 5 years on . It's in a air conditioned environment . I understood that as long as you have maintained it you ( 70E ) said you can operate it . I choose to use the PPE as a extra precaution . I asked the question as with some of the previous posts I've seen it can get confusing about PPE and operating a switch or a breaker . The sticker " PROHIBITED " was put on it after we had the arc flash study done .
Then you technically don't need PPE per 70E with the doors closed for normal operations. But resetting it after a fault for example would not be normal so PPE should be worn (Or remote operators)
 

wbdvt

Senior Member
With such a high IE, I am curious to know if the utility actual available fault current was used or was it an infinite bus fault current at the transformer secondaries?

If modeled with utility actual available fault currents and utilizing the utility protective device on the primary side, your values may be lower.
 

Davebones

Senior Member
The electrical engineer contacted the utility and they did the study with what the utility said was the available fault current .
 

wbdvt

Senior Member
The electrical engineer contacted the utility and they did the study with what the utility said was the available fault current .
That could be the issue. As an engineer that has done many studies, the first time I request the available fault current, a customer service person provides me with the infinite bus fault current based on installed transformer size. It sometimes takes some effort to get the right info.

I also will model from the utility's riser fuse. This way the actual incident energy is known at the service entrance equipment as credit can be taken for the riser fuse protection and an arbitrary cutoff time of 2 seconds is not used.

That result seems extremely high.
 

powerpete69

Member
At our plant we service our large draw out breakers every 3 years on a rotation. They are inspected, tested, lubricated, cleaned and or replaced. Sometimes taken completely apart, re-zinced parts and re-tinned terminals. The same is done for the relay and trip units.

For the modeling of your arc flash, there is a selection in your arc flash tab. You can select "include main breaker" or "exclude main breaker". This significantly changes your calories on the secondary of a transformer switchgear.

In typical pullout switchgear, the main breaker is in a different compartment from the rest of the breakers. For the main breaker compartment, you want to "exclude the main breaker" because the line side of the breaker will cause the most arc flash. This will have a large arc flash rating, put the big sticker on that compartment.

For all the downstream breaker compartments that are separate, you want to select "include main breaker" for all these compartments because the line side of the main breaker is no longer in play. This will significantly reduce your arc flash calories in these downstream compartments because that main breaker will significantly reduce arc flash. Use the smaller calorie stickers for these feeder breakers in this case.

For example, on a 2300 KVA transformer with a main breaker and a fuse before the primary of transformer, 4160V to 480V, 3200 Amp breaker, if I EXCLUDE the main breaker, the calories are 73 per cm squared on the line side of that breaker, which is correct for main breaker compartment. If I click the INCLUDE main breaker for all the feeder breakers in different cabinets, the bus now drops to 18 calories per cm squared, big difference!!!

In a typical I line panel, the main breaker is wide open to the rest of the panel with the cover removed. The line side of the breaker is exposed, therefore, you must use the worst case for the whole panel, "EXCLUDE" main breaker.

In your case, you have molded case breakers and switches. Is the main breaker in a separate compartment from the rest of the breakers? Either way, exclude main breaker calculation for that main breaker compartment. Is the main breaker open to the rest of the feeder breakers? If so, exclude main breaker calculation for all the feeder breakers as well. If main breaker is in its own compartment, include the main breaker calculation for all downstream breakers and their arc flash stickers which will be much less calories.

173 calories per cm squared sounds real high. Something likely not quite right. My 2300 KVA example above I bet is pretty close to your bigger 4000 amp breaker situation. However, if there is no fuse before the primary of the transformer, perhaps 173 calories is correct.

When your compartments are closed tightly as in your case, arc flash is theoretically not suppose to be able to jump out and get you. "Theoretically".

That being said, I would personally still wear a 40 calorie full suit when switching any of these breakers or switches in your case with the compartments COMPLETELY closed.

Also, look into getting your gear cleaned, serviced, etc. Dust is a big player in arc flash accidents. Faulty breakers are also a big player in arc flash accidents. Although you can't service or replace molded case breakers, you can certainly test them and replace bad ones. Get the primary of the transformer completely turned off before attempting to service the internals of this electrical gear!
 

ron

Senior Member
That result seems extremely high.
I have found the opposite results.
The utility fusing is often very lenient and with any relatively stiff source (I work on large systems), the let through energy to the facility's line side switch is often pretty high in my studies using real available currents. With the "Smart" grid, the path of power flow on the grid is dynamic and the highest path needs to be considered through the transformer.
 

wbdvt

Senior Member
For the modeling of your arc flash, there is a selection in your arc flash tab. You can select "include main breaker" or "exclude main breaker". This significantly changes your calories on the secondary of a transformer switchgear.

In typical pullout switchgear, the main breaker is in a different compartment from the rest of the breakers. For the main breaker compartment, you want to "exclude the main breaker" because the line side of the breaker will cause the most arc flash. This will have a large arc flash rating, put the big sticker on that compartment.

For all the downstream breaker compartments that are separate, you want to select "include main breaker" for all these compartments because the line side of the main breaker is no longer in play. This will significantly reduce your arc flash calories in these downstream compartments because that main breaker will significantly reduce arc flash. Use the smaller calorie stickers for these feeder breakers in this case.


When your compartments are closed tightly as in your case, arc flash is theoretically not suppose to be able to jump out and get you. "Theoretically".

That being said, I would personally still wear a 40 calorie full suit when switching any of these breakers or switches in your case with the compartments COMPLETELY closed.
Even though the main breaker is in a different compartment does not mean it can be included to use for arc flash. The fault pressure and ionizing gases can get past any sheet metal barrier and cause the line side terminals to arc, thereby continuing the arcing fault. Unless the equipment has been tested and given an arc resistant rating/certification, I would never include a main breaker that is in the same line up as the other breakers to interrupt the fault. I would not want to be deposed or on the witness stand justifying that decision to include the main breaker when there is so many unknowns and prevailing wisdom has been to not include the main breaker.
 

powerpete69

Member
Even though the main breaker is in a different compartment does not mean it can be included to use for arc flash. The fault pressure and ionizing gases can get past any sheet metal barrier and cause the line side terminals to arc, thereby continuing the arcing fault. Unless the equipment has been tested and given an arc resistant rating/certification, I would never include a main breaker that is in the same line up as the other breakers to interrupt the fault. I would not want to be deposed or on the witness stand justifying that decision to include the main breaker when there is so many unknowns and prevailing wisdom has been to not include the main breaker.
I would certainly agree that engineering judgment needs to be used when determining arc flash parameters. Most cases you do need to exclude the main breaker. However, there are some cases where you can include the main breaker in a lineup.
In a MLO panel, you can always include the main breaker for the arc flash study since the line side of the main breaker is not in the panel in question.
 
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