Arc Flash 480V vs 208V panels

[Davebones]

Just had SQ D finish up labeling panels for the Arc Flash study that we "FINALLY" got management to do . Thay did all of our panels in the plant . Really amazed at how high some of the 208V & 240V panels energy levels were . These were on systems feed from 480V to 208V , 75KVA to 225KVA . Just wanted to say how a lot of electricians don't understand how dangerous 208V , 240V panels can be . Heard it just the other day from a electrical contractor " It's just 208V " !

 

[augie47]

I am surprised you have a real high fault current on the secondary of a transformer as low as 75 kva.

 

[ron]

I am surprised you have a real high fault current on the secondary of a transformer as low as 75 kva.

Generally the high incident energy is due to low fault current. The protective devices are inverse time.

 

[augie47]

Interesting. Makes sense now that I think about it.

 

[zog]

I am surprised you have a real high fault current on the secondary of a transformer as low as 75 kva.

Me too, the general opinion is that a arc <240V fed at 112.5kVA or less will not self sustain, thus no duration. However there is some research that disputes that claim which is why it was removed from the 70E. Still in IEEE 1584 though.