Arc Flash Reduction Maintenance Switch

[djr3203]

We have a project where we will be installing a new Eaton Magnum DS Low Voltage Switchgear with an arc flash reduction maintenance switch.

1. Does the maintenance switch set the main breakers to their lowest settings to reduce arc flash hazard while working on the gear?

2. If so, should the arc flash label posted on the gear be based on the settings when the maintenance switch has been switche? Or should the label assume the switch hasn't been activated?

Thanks for the help all.

DJR

 

[dpc]

1. It's a MANUALLY operated setting that will activate a very sensitive instantaneous trip element. Workers must remember to put the Maintenance Mode switch in Maintenance Mode and they must remember to put it back to normal when the work is completed. While in Maintenance Mode, selectivity (coordination) between the breakers is sacrificed in order to reduce the incident energy. There should be some feedback provided indicating that the trip unit is in maintenance mode.

2. Good question. The standards do not address this. My recommendation is to use a label based on the maintenance mode being OFF, since this will be the worst case. The effect of the maintenance mode can (and should) be covered in the required Energized Work Permit. If you base the label on the use of the Maintenance Mode, this needs to be very clearly called out on the label.

 

[davidbeach]

Two labels? One for each condition. Might get peoples attention and understanding as to why maintenance mode is their friend.

 

[dpc]

Yes, two labels is another option. This approach runs the risk of someone just picking the label they like best. It all comes down to proper training. The labels are only one part of the program.

 

[jraef]

I have taken the approach that the label assumes the worst case scenario. The only people that should have access to the Maintenance Mode switch are going to be qualified workers who will be following an established procedure WRT PPE, hot work permits, etc. That procedure would include operation and verification of the Maintenance Mode, then the corresponding slightly lower PPE requirement for those qualified to use it.

If you have two label, and an unqualified worker does not understand the meanings, then the fact that there is potential confusion can lead to an unsafe situation.


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

 

[jghrist]

I disagree. If you have a label that says where PPE for 36 cal/cm², and the work permits allows 7 cal/cm², based on operating in Maintenance Mode, this tells the workers that you don't always have to use the PPE listed on the label for hot work. I think that the work permit should require operating in Maintenance Mode. No hot work should be done unless you are in Maintenance Mode. This should be part of the training and the Electrical Safety Program.

 

[HamburgerHelper]

Are people leery about the effectiveness of using light sensor to detect an arc event? If I were a plant manager, I might want this rather than run the risk of maintenance forgetting put the switch back into normal mode.

 

[djr3203]

All,

I think you all have very good points, and I feel the topic could be argued to eternity... I guess no matter what, it falls on the worker to read labels prior to working and to follow procedures (and hopefully the employer has put in place good maintenance procedures).

Hamburger,

Light sensor to detect an arc event? I am failing to grasp what you mean by this?

DJR

 

[wbd]

By light sensor, I believe a arc flash detection relay such as ABB REA 101 is being referred to. This type of relay will react to overcurrent plus light to initiate a trip of the breaker. These are very fast acting relays around 3 mSec. The flash is sensed by fiber optic sensors (either continuous cable or spot sensors) carefully routed thru all switchgear compartments and coupled with a current input to prevent false tripping

 

[unclebob]

If I had the option of using the arc flash maintenance switch, or the ''light sensor'', or an arc resistance gear, I would use all of them.
As for the stickers, I met a poor USB gear wearing 4 stickers, with categories going from 1 to 4. Seriously... I prefer the worst case scenario and put only one label.

Bob

 

[stevenal]

Even if suited for the task, why would anyone be interacting in a way likely to cause an arc flash event without activating maintenance mode? And the non-qualified folks should not be interacting at all, and should be well back when someone else is. I'm with jghrist on this.

 

[dpc]

Why? Because human beings are involved and we always have the potential to do something really stupid. Industrial facilities often have a variety of contractors doing work on site. It's much different than a utility environment.

 

[DanDel]

I prefer to use the worst-case values on the attached label onsite, and keep the labels with the values from the maintenance-mode settings in a book kept secured by the facility maintenance manager. Since the worst-case labels are in effect for the vast majority of the time the equipment is in service, there will be no chance of a worker using the wrong PPE. And when the maintenance-mode settings are desired to be used for temporarily, the maintenance manager will be notified and involved in the procedure, provide the applicable hazard limits and PPE information needed, and then verify that everything is set back to normal and the book secured when the procedure is finished.

 

[wroggent]

If unqualified people are going to service the equipment I feel like those people aren't going to pay attention to the label at all anyway. Why not just label everything as no safe PPE and death is guaranteed if they touch it? When qualified people need to work on stuff get out your secret book and look up the real incident energy value.

 

[HamburgerHelper]

Djr

It is a fiber optic sensor as mentioned above. Schweitzer has been pushing their sel-751a which has it. If you want to read about it, look up the ieee pes magazine issue from 2011 that focuses on arc flash. There they compare a bunch of different methods for mitigation. The one I always thought was odd but I think it was the quickest was to crowbar the 3 phases to extiguish the arc.

 

[stevenal]

The assumption seems to be that too much protection is not harmful. I disagree. I also disagree that contractors are somehow different. And the vast majority of the time no interaction is taking place so no PPE is needed at all. Some scenarios to consider:

Scenario 1:

Company uses worst case labeling. A qualified worker dons PPE per the label prior to interacting with the circuit. Worker puts upstream device in maintenance mode significantly reducing IE from that shown on the label. Result: Possible injury due to unnecessary restriction of movement, sight, or overheating from oversized PPE, and violation of 70E 130.7(C) (9)(f)

Scenario 2:

Company uses worst case labeling. A qualified worker dons PPE per the label prior to an interacting with the circuit. Although provided, worker fails to put upstream device in maintenance mode. Although dressed for the potential IE, worker is still subjected to unnecessary restriction of movement, sight, or overheating; as well as being exposed to a higher than necessary potential IE. All these unnecessary risks due to the failure to use maintenance mode and use properly selected PPE for the task.

Scenario 3:

Company uses worst case labeling. A qualified worker ignores the label and instead goes to the book to select PPE for use during maintenance mode per company policy. Worker puts upstream device in maintenance mode significantly reducing IE from that shown on the label. Worker is not unnecessarily exposed to potential IE or the hazard of using oversized PPE for the task. The apprentice watching all of this is taught that labels are useless and should be ignored.

 

[dpc]

Stevenal,

What about the scenario where an Energized Work Permit is created, as required by NFPA 70E, and it specifies use of Maintenance Mode for this task and list the appropriate and correct PPE - and everyone live happily ever after?

And the vast majority of the time no interaction is taking place so no PPE is needed at all.

This doesn't seem relevant to the question at hand.

The argument that wearing PPE creates additional safety hazards has always been popular with those who are looking for reasons to not wear it. It can be a valid concern, depending the equipment, the location and the task to be performed, but in general it is very over-used IMO.

I still prefer to label for the worst-case, but I recognize that there are other valid approaches. There are many roads to Dublin. And wearing any PPE is better than wearing none.

 

[stevenal]

What about the scenario where an Energized Work Permit is created, as required by NFPA 70E, and it specifies use of Maintenance Mode for this task and list the appropriate and correct PPE - and everyone live happily ever after?

Scenario 3. I neglected to include the permit, but it's the same outcome. Any observer will see the label requirements are being ignored every time energized work is performed.

This doesn't seem relevant to the question at hand.

Thanks for seeing my point. I was responding to Dandel.