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 Post subject: Protective device/Labeling
PostPosted: Fri Dec 25, 2009 4:40 pm 
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Joined: Fri Dec 04, 2009 8:15 pm
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Location: washington
Recently a Arc Flash Study was completed at my facility-several of the labels list the protective device as being a feeder,i.e. a conductor-Iam not an engineer but something tells me this is wrong.What do you think? :confused:


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PostPosted: Sun Dec 27, 2009 11:35 pm 
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I don't see anything wrong with the label. Feeders and conductor wording doesn't really apply because you are not going to be working on live cables that are also bare. You'll be inside enclosures. But they are just stating the source of the energy.


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PostPosted: Mon Dec 28, 2009 11:29 am 
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Location: Lawrenceburg KY
AF Label

Looks like a good professional label.
Appears we are looking at a busplug device, I assume BP is a Bus plug + ### is the location.

As haze says this feeder (FDR) is only equipment type being indentified (e.g. feeder, wire, steel conduit, cable, etc.) to show mainly how the impedance is based towards calculation of the upstream protective device.

You should ask the person conducting the study to provide a nomenclature and method of protective device numbering to completely understand their intentions. The engineering firm would usually include this in the final executive report. This document should be on file with your company.


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PostPosted: Tue Dec 29, 2009 1:59 pm 
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You should ask the guy who designed the label to interpret it. As far as I understand, the FDR doesn't necessarily mean the cable that is providing the protection. It is probably refering to the feeder breaker on that equipment. Do you have labels that say Main to BP****?

Depending on the magnitude of fault current backfed from motors or stand by generators, it is quite possible for a feeder breaker to trip for a fault on the bus it is connected to. Obviously, your main breaker would trip in this case as well but it wouldn't clear 80% of arcing fault current.


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PostPosted: Wed Dec 30, 2009 9:01 am 
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There should be a one-line diagram that has the same nomenclature as the labels.


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PostPosted: Wed Dec 30, 2009 12:36 pm 
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amohammed wrote:
FDR doesn't necessarily mean the cable that is providing the protection. It is probably refering to the feeder breaker on that equipment. Do you have labels that say Main to BP****?


Good thought. I agree on your remark of the FDR. I also, name the upstream device on my labels. I did not catch that one. When responding earlier.
Thanks


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PostPosted: Fri Jan 01, 2010 2:17 pm 
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What I find interesting is that, at the bottom of the label, it states that this is Scenario 1 - Utility maximum - motors on.

I have found that typically the worst case for arc flash is with utility a minimum. So did they run several scenarios and find that utility maximum - motors on is worst than utility minimum - no motors on? This should be stated in the report. :confused:

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PostPosted: Sat Jan 02, 2010 2:18 pm 
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wbd wrote:
What I find interesting is that, at the bottom of the label, it states that this is Scenario 1 - Utility maximum - motors on.

I have found that typically the worst case for arc flash is with utility a minimum. So did they run several scenarios and find that utility maximum - motors on is worst than utility minimum - no motors on? This should be stated in the report. :confused:


As you may know you should have several scenario's built in the software when doing the AF study. Yes, I understand your confusion. But this scenario may be worse do to the company having large motors that contribute to the overall short circuit current. The motor contribution is the main player I suppose in this case.


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PostPosted: Mon Jan 04, 2010 8:12 am 
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If they have conducted the study using SKM's PTW then the results would surely have been pulled from the scenario which had the worst case incident energy for each piece of equipment.


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