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Arc Flash Evaluation for Single Phase Equipment

Arc Flash Evaluation for Single Phase Equipment

Arc Flash Evaluation for Single Phase Equipment

(OP)
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?

RE: Arc Flash Evaluation for Single Phase Equipment

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.  



RE: Arc Flash Evaluation for Single Phase Equipment

(OP)
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.  

RE: Arc Flash Evaluation for Single Phase Equipment

Dumbo,

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

Mike

RE: Arc Flash Evaluation for Single Phase Equipment

(OP)
Unfortunatley the customers typically require all panels to labeled.

RE: Arc Flash Evaluation for Single Phase Equipment

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.

RE: Arc Flash Evaluation for Single Phase Equipment

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.  

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