Arc Flash Calculation at voltages over 15 kV

[lume7006]

Hello everybody,

I know that IEEE Std 1584 is valid only in voltages up to 15 kV and for voltages above it, Lee equations are applicable.
Does anyboy have an example or reference that shows in detail the way to calculate the incident energy, distances and so on?

We have followed the Lee equations and the results are not believable in all cases, despite having very fast trip times and fault currents in the range of 5 kA at 34.5 kV, incident energy is over 100 cal/cm2.

I thank you in advance for your help!

 

[stevenal]

Sounds like you did it right. Lee is voltage dependent and extremely high values come out at higher voltages. If you have 1584, the spreadsheet that comes with it transitions to LEE above 15.
Suggest ArcPro.

 

[lume7006]

Dear stevenal,

I thank your comment.
One final point:
And the results are believable? despite being 100 cal/cm2?
What do people typically do?

Because, you would need a very extreme clothes, distances of more than 100 meters and so on.


Best Regards

 

[stevenal]

No they are not believable. Incident energy is generally not considered to be voltage dependent assuming there is sufficient voltage to sustain the arc.

 

[jghrist]

Is the equipment in question open or enclosed? If it is open, it may be more suitable to use ARC-PRO which was used to prepare the NESC HV arc hazard tables. ARC-PRO is for open air where spacings are such that arcs probable won't develop into 3Ø faults.

 

[stevenal]

There are multipliers for ArcPro results that can be used for three phase and enclosed arcs. Still may be better than using Lee.