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 Post subject: Non-electrical worker turning off 3PH 480 Panelboard Circuit Breaker?
PostPosted: Thu Nov 29, 2012 10:39 am 
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Location: Lawrenceburg KY
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I have 3Ph lighting panel board 277/480V with breakers. Now normally the operators would not be working around this panel nor have any need to be switching. The hazard study indicates this panel board is a CAT 0 hazard with the covers removed. I am looking at putting in our arc flash policy the points that operators are not allowed to operate switches at in the facility. Normal maintained equipment with low hazard ratings of CAT 0 in which the operator has been trained to recognize and avoid the hazards and qualified in the functions of the equipment will be allowed to LOTO control panels, circuit breakers and safety disconnect switches as long as the operator LOTO placard has identified the LOTO point to safely remove the hazard. This would allow equipment/machine operators to turn of the equipment power on their machine for specific task of cleaning or preventive maintenance in areas identified by a hazard risk analysis and the placard has identified the source of the energy. The operator is trained that the switching device must be in a secured enclosure at all times and recognizes the hazards. The operator wears safety glasses, steel toe shoes and hearing protection.

The 277/480 panel board hazard is low but without hand PPE this may not be safe to interact because the panel is not a total enclosed system as it being a breaker panel. Any thoughts?

1.No machine operator shall switch or de-energize a bus way fused switch. This system is located approximately 30 feet off the floor and contains high levels of hazardous energies. (Cat2-3 hazard level)

2.No machine operator shall switch or de-energize a HV (>240V) 3 Phase circuit breaker within an enclosed panel board or circuit breaker panel. The system is not totally enclosed. Previous incidents in industry have found this hazardous and special PPE may be required in some cases. (Cat 0)

3.No machine operator shall switch or de-energize the plants main switchgear systems. The area is for authorized employees only and contains hazardous energies. (High Danger)


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PostPosted: Thu Nov 29, 2012 5:44 pm 
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Qualified personnel are qualified to perform certain tasks and use certain work methods. Your "qualified" electricians for instance may not be qualified to work on 69 kV lines, to say nothing of using live-line, bare-hands methods on 345 kV transmission lines. Conversely the transmission line guys probably need to stay out of 480 V or even 120 V panelboards. Just because someone is "qualified" does not necessarily mean that they will need to be trained on how to deal with an exposed, energized line. The limit of their training may be only to avoid such hazards in the first place and to report them to someone else who is qualified to deal with such things. So the clerks in the front office are probably qualified to operate light switches and plug in a coffee maker. They would not be anywhere near qualified to operate some (many) power tools.

Do you see what I'm saying. "Qualified" does not automatically mean "electrician". It means having the knowledge and skills necessary to perform certain tasks using certain work methods and to be able to successfully recognize and respond to the hazards involved in those tasks appropriately. There is no such thing as a "super electrician" that can work equally well on house wiring, on complicated 480 V drive systems in a large paper mill, and on 345 kV overhead transmission lines.

THE CABLE GUY wrote:
The 277/480 panel board hazard is low but without hand PPE this may not be safe to interact because the panel is not a total enclosed system as it being a breaker panel. Any thoughts?


Now we get to the rather interesting part. The question you need to ask yourself is what is the RISK. You've described the hazard, sort of. You mentioned H/RC 0 several times. In other words, what would be the required PPE to ensure with high probability (95% confidence according to IEEE 1584) that it is not fatal. What you are seriously missing here though is considering what the risk is...in other words, what is the hazard, and what is the likelihood that it may occur. Although it is pretty much guaranteed that if you are struck by a meteor, you will die, we don't install meteor shields over parking lots because the likelihood of you being struck by a meteor on your way from your vehicle to the office is extremely small. By the same token you need to look at arc flash the same way to determine whether or not such things are required. That is why the 70E Technical Committee in their table assigned a value of "0" for operating breakers on 480 V panelboards but used the actual incident energy value for other activities. IEEE 493 data suggests that under average conditions the likelihood of an arcing fault is very low. However, if it is known that the breaker is contaminated, corroded, a fork truck just crashed into the panel, or the breaker just tripped (see NEMA AB-4, available for free, and widely published as the reference standard for molded case breakers), pending an inspection by your electricians, you cannot make the assumption that the likelihood is still very low. Thus if your qualified personnel are not trained to inspect the breaker (and perhaps other equipment especially with IEC Type 1 motor protection), then they just became unqualified to operate the breaker and more qualified personnel have to move in.

Quote:
1.No machine operator shall switch or de-energize a bus way fused switch. This system is located approximately 30 feet off the floor and contains high levels of hazardous energies. (Cat2-3 hazard level)


Interesting. There are lots of reasons why you'd want to avoid this. Many times these switches don't have a mechanical "snap action" so training is required on how to open/close them properly without causing an instant arcing fault or welding the contacts. But with the equipment located so far away there is probably not a significant incident energy at the working distance of 24 feet (trying to read from your description), or 2880 inches. That happens at my work place. The incident energy on overhead distribution lines is minimal at 10 feet distance, the working distance for the hot sticks that we use. Still though all operators and most electricians are not trained to energize equipment by putting saddles on the lines and attaching jumpers, so only linemen are qualified.

Quote:
2.No machine operator shall switch or de-energize a HV (>240V) 3 Phase circuit breaker within an enclosed panel board or circuit breaker panel. The system is not totally enclosed. Previous incidents in industry have found this hazardous and special PPE may be required in some cases. (Cat 0)


It's not a matter of being enclosed (unless you have old, open switch gear and not metal clad or metal enclosed). It's more a matter of how again it is designed. The major hazard from this equipment in the plant I work at is that with much of it, "lock out" means that you have to move the breaker out of the cell. 80% of failures in this equipment (all arcing) occur during racking breakers, either in or out. This equipment is an order of magnitude less reliable than bolted in breakers. Even non-enclosed gear is not necessarily "exposed" using NFPA 70E standards. For instance, the bus gear switches you described earlier, even if the busbar is open and clearly visible are not exposed because they are not accessible normally. This situation could change for instance if you were in a scissor lift or built scaffolding under it.

Quote:
3.No machine operator shall switch or de-energize the plants main switchgear systems. The area is for authorized employees only and contains hazardous energies. (High Danger)


I'd avoid using words like "high danger". It gives electricians that are required to work on it the wrong impression. Those areas are simply accessible to authorized personnel only (qualified electricians). Simple as that. NEC is pretty clear about this for >600 V switchgear. And once again, NEC has a similar wording of "qualified" vs. "unqualified".


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PostPosted: Fri Nov 30, 2012 11:04 am 
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Thanks Paul


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