Info Source for LV / MC Ratings

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charlie b

charlie b

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Semi-Retired Electrical Engineer
A client is asking for vast great deals of information to be placed on the one-line diagrams for a set of new buildings. I think they might be asking for some things that do not apply. Two examples:

? For 480/277 Volt Switchgear, they want ?Asymmetrical Momentary/Closing and Latching Current Ratings for Main, Tie, and Feeder Breakers.? They also want ?MVA Class.?
? For 480/277 Volt Switchgear and Distribution Panels, they want ?Symmetrical Interrupting Rating.? The also want ?KVA Class.?

I think these apply to medium voltage switchgear, but not to 480/277 volt switchgear and distribution panels.

Any thoughts? What information source(s) should I look for, in order to find out what standard ratings apply to what voltage class of equipment?
 
Charlie,

You are correct that a KVA class rating does not have anything to do with low voltage switchgear, and although I am not as old as dirt, I don't recall it ever being referred to that way. the following is from IEEE C37.20.1
View attachment 431

As far as Medium Voltage, C37.09-1999 went away from MVA ratings for medium voltage gear, and went to straight KA rating. This was when they took the "k" factor, set it to "1" and made the KA rating applicable to all voltages in that class. Breakers prior to 1999, would still fall under the old rating. Cutler Hammer has a nice section in their catalog that provides good info on this.

In general, IEEE C37 would be the place for LV and MV gear.

Sounds like your client needs a little polite schooling, Good Luck.
 
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