Last week's question of the week stirred up an interesting discussion about using the IEEE 1584 equations above 15 kV. This lead to this week's QOW.

Have you/anyone you know ever used the IEEE 1584 equations above 15 kV?

Yes
No

The question is a little bit ambiguous as there are two different calculation modes included in IEEE 1584 (excluding fuse and breaker equations that are too restrictive and limited to one manufacturer products only anyway). Therefore, I chose "Yes" as the answer.

Specifically, IEEE 1584 provides Empirical Model equations for voltages in the range of 208 to 15,000V and gaps in the 13 to 152 mm range. For cases where voltage is over 15kV, or gap is outside the range of the model, IEEE 1584 recommends using the theoretically derived Lee method. The Lee method formulas are part of IEEE 1584 and they are listed in the IEEE guide sections 5.4 and 5.5.

Thanks Arcad. I did not think about this interpretation. The intent of the question is this. There are presently 4 empirically derived equations that are part of the existing IEEE 1584 model.

1) arcing short circuit current < 1kV
2) arcing short circuit current > 1 kV
3) incident energy (actually 2 equations including normalized and adjusted)
4) arc flash boundary

These equations have a range of validity from 208V through 15 kV

The questions is regarding these IEEE equations and NOT the Lee or other methods referenced in the standard.

Thanks for bringing up the ambiguity!

When using software program for arc flash analysis, you would rely on the program intellect selecting right calculation mode and applying appropriate equations for arc flash current, incident energy and arc flash boundary calculations based on input information like system voltage, gap between conductors value etc.

You don't really have to know which equations are being applied unless you are performing the calculations manually. Hence, you wouldn't typically know answer to the question of the week

Arcad,

I agree completely. The beauty of arc flash software!

This was just a follow up to a comment last week about people using 1584 above 15 kV. PaulEngr made some good comments last week too.

You would really have to go out of your way to use IEEE 1584 incorrectly. The data tables don't even go beyond 15 kV for gaps, X values etc. so this type of data would be a complete guess or made up. Or as you pointed out, misinterpreted the question and included Lee since it is technically included as part of the IEEE 1584 standard.

Good comment! After looking at the actual IEEE 1584 standard yesterday, I don't even know how someone could use the equations beyond 15 kV. They would have to literally pull numbers out of thin air for certain parameters since they don't exist at higher voltages. That doesn't even make sense.

This seems like an odd question. I assumed it was obvious (assuming you read the standard) that you can't use the IEEE equations above 15 kV.