LV & Single Phase Arc Flash

[lansford]

It is common knowledge and often noted that IEEE 1584 does not apply to LV single phase systems and the results are conservative for example 240 volts three phase systems sourced from "small transformers" as well.
Plant electrical personnel quickly loose confidence in arc flash studies (labels) where
a) a single phase 240/120 volt panel sourced from a 25 KVA, 480 v primary transf. OR
b) a 240 volt three phase panel sourced from a 45 kVA, 480 volt primary transf.
Show high levels of arc flash energy (labels)
and the IEEE 1584 exception < 125 KVA < 240 volts (208v) as well as calculations on 480 volt systems may yield low levels of arc flash energy (label)

Yes you can use the equivalent three phase model to model single phase but these often result in the same issues as noted.
I think the best approach for the single phase issue excluding the use of Heat Flux or ArcPro software is to use a simple software that documents to conform to NFPA 70E and parts of IEEE 1584 for single phase and use the major commercial software for three phase.
This is what I think is my best option even though it takes time to get the labels to look similar.

For case b) I don't have an easy answer.
thanks for comments

 

[waross]

Regulations pertaining to arc flash awareness and arc flash studies are a work in progress. I have no doubt that the regulations will continue to evolve to include lower voltages and lower power levels.
That is the nature of regulators and regulations.

Bill
--------------------
"Why not the best?"
Jimmy Carter