Arc Flash Analysis For Utilities

Arc Pro Questions

I was recently in contact with a person at kinectrics (www.kinectrics.com) 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.