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 Post subject: Arc Flash Analysis For Utilities
PostPosted: Sun Dec 23, 2007 6:10 pm 
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Joined: Sun Dec 23, 2007 1:44 pm
Posts: 348
Location: Charlotte, NC
As a utility electrical engineer for the past 28 years, NESC 2007-Part 4 is the most bewildering and confusing standard I have encountered. Seems not unlike many who use this forum. I am searching for software that will accurately model an overhead utility distribution system with phase spacings obviously greater than 153 mm. Seems ArcPro might be the preferred with many. Any suggestions or comments appreciated....Alan

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PostPosted: Mon Dec 31, 2007 7:12 am 
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Joined: Mon Sep 17, 2007 5:00 pm
Posts: 1682
Location: Scottsdale, Arizona
Arc Pro Questions

I was recently in contact with a person at kinectrics ( that handles Arc Pro and he said he understood it was used as part of the development of the NESC tables but he could not directly confirm it. I have not run the numbers myself but perhaps someone else in the forum has.

The big issue as many here have noted is arc flash calculations on overhead lines are not usually considered there phase events and therefore the calculated energy is different (typically lower) than the IEEE three phase model. Although Line-Ground faults can have a greater magnitude than three phase faults depending on the zero sequence impedance and grounding configuration, the energy released with one phase arcing is still less than three phases arcing together.

It appears the goal of the NESC is to mandate the analysis and leave it up to the individual organizations to determine how. This is similar to the approach that NFPA 70E took. Many will likely use tables initially in the absence of a clear understanding of the calculations but later migrate towards some form of calculations.

Many utilities that I have worked with are using calculations now i.e. programs like Arc Pro for overhead and EasyPower, SKM etc. for equipment, but many are scratching their heads and using the tables initially.

Jim Phillips, P.E.

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PostPosted: Thu Feb 14, 2008 12:09 pm 

Joined: Thu Feb 14, 2008 12:04 pm
Posts: 4
ArcFlash Hazard Assessments for Utility

We have completed the majority of our assessments. We used ARCPRO for above 1kV and EasyPower/IEEE1584 for below.

We have done extensive arc testing in our laboratory to complement the assumptions and are embarking on more testing to validate the calculation formulas and assumptions for typical utility equipment 480V and below.

I can verify first hand that ARCPRO is the base for NESC because I helped them with the tables.

Marcia Eblen
Principal Grounding Engineer-Pacific Gas & Electric

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