Arc Flash Evaluation for Single Phase Equipment

[Dumbo2929]

I was wondering what people are doing as part of arc flash evaluations when you have both 3-phase and single-phase equipment (panels, etc.) My experience is that some arc flash software ignores single phase equipment and that it is somewhat ignored in NFPA-70E. It seems silly to have a HRC/PPE specific label on a 3-phase panel and have a single-phase panel right next to it with no label. Any thoughts?

 

[dpc]

Single-phase 240V panels are discussed in IEEE-1584. Their recommendation is to model them as an equivalent three-phase 240V panel. The IEEE-1584 arc-flash equations are all based on three-phase faults. The results should be conservative.

 

[Dumbo2929]

I can model them as 3-phase, but them I have to model the upstream transformers as 3-phase (75kVA vs. 25kVA for example). It just complicates things.

 

[mpparent]

Dumbo,

The standard allows you to ignore xfmr's below 125kVA (480-208/120V systems).

Mike

 

[Dumbo2929]

Unfortunatley the customers typically require all panels to labeled.

 

[dbaird]

You might want to go to:

http://www.arcflash.com/

They have arcflash shareware ("Duke Power Heat Flux Calculator") that allows for 120VAC calculations.

David Baird

Sr Controls Designer
EET degree.
Journeyman Electrician.

 

[dpc]

Yes, you have to model the transformers as three-phase as well.

IEEE-1584 recommends that ALL 240V systems be evaluated. For 208V systems, they recommend evaluation for systems 125 kvA and larger. 240V and 208V are treated differently.