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 Post subject: 120 Volt arc flash
PostPosted: Fri Nov 11, 2016 8:10 am 
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I believe it to physically impossible to sustain an arc flash at 120 V but can someone point me to the proof? Can someone indicate where a code specifically states no arc flash PPE is required at 120 VAC?


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 Post subject: Re: 120 Volt arc flash
PostPosted: Fri Nov 11, 2016 9:17 am 
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Location: North Carolina
williamrucki wrote:
I believe it to physically impossible to sustain an arc flash at 120 V but can someone point me to the proof? Can someone indicate where a code specifically states no arc flash PPE is required at 120 VAC?


https://drive.google.com/file/d/0B6mGRC ... lDSWM/view

I collected what exists all in one place. There's nothing per se saying it but no research I've seen so far says that it is possible.


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 Post subject: Re: 120 Volt arc flash
PostPosted: Fri Nov 11, 2016 9:23 am 
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Thank you very kindle for the ultrafast response.

Bill


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 Post subject: Re: 120 Volt arc flash
PostPosted: Mon Nov 28, 2016 8:52 am 
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William - see if these two references help...

208-V Arc Flash Testing: Network Protectors and Meters. EPRI, Palo Alto, CA: 2010.
1022218

US Dept. of Labor, Interpretation Letter, 07/13/2015 – Selecting protective clothing based on
the IEEE National Electrical Safety Code, C-2, 2012


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 Post subject: Re: 120 Volt arc flash
PostPosted: Mon Nov 28, 2016 9:48 am 
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jdlaw1 wrote:
William - see if these two references help...

208-V Arc Flash Testing: Network Protectors and Meters. EPRI, Palo Alto, CA: 2010.
1022218

US Dept. of Labor, Interpretation Letter, 07/13/2015 – Selecting protective clothing based on
the IEEE National Electrical Safety Code, C-2, 2012


Eblen's testing (under EPRI) by the way is looking at what might be some rather extreme cases. High available fault currents with a type of meter socket that essentially looks like a rail gun tend to throw plasma out of them during a fault and give really high incident energy, and network protectors have the basic problem that it's really just about impossible to figure out what the "available fault current" is at any given time. There is at least one OSHA documented incident with each of these where a fatality occurred and so EPRI did equipment-specific testing on that type of equipment.

It is also very close to the threshold where incident energies start to climb. I used that one in my collection as well. I have not been able to nail down a specific threshold but somewhere in the neighborhood of 200-300 VAC is the point where almost irrespective of the available fault current and other initial conditions, incident energy won't get over 1.2 cal/cm2 to the point where even if the incident energy is less than predicted by the various equations, it is still high enough to be a concern.


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