switchgear short circuit ratings
switchgear short circuit ratings
(OP)
We have an old medium voltage Allis-Chalmers switchgear system. The breakers are rated for 1200A, and 29KA interrupting rating. The e-tap model shows a 3-phase bus fault value of 40KA. This is all contribution at the bus these breakers are connected to. My question is, when we are considering bus fault, should we be looking at bus or breaker short circuit rating?





RE: switchgear short circuit ratings
Some programs can compute the individual breaker duties automatically. I don't know about ETAP.
Since it appears your breakers may be underrated or at least close to it, you may also need to consult ANSI C37 to make sure your software is calculating the fault duty in accordance with the ANSI requirements for that vintage breaker.
It looks like there may be some problems, based on the data you have provided.
RE: switchgear short circuit ratings
RE: switchgear short circuit ratings
If you're within 80% or so of the breaker rating, you should probably do an ANSI C37 calc. Maybe that is what ETAP is giving you - not sure. But it is not a straight Ohm's Law network reduction.
RE: switchgear short circuit ratings
RE: switchgear short circuit ratings
RE: switchgear short circuit ratings
If you're really up against it you could check with these guys about their CLIP device:
http://ww
But the best solution is to upgrade the breakers.
RE: switchgear short circuit ratings
RE: switchgear short circuit ratings
RE: switchgear short circuit ratings
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If we learn from our mistakes I'm getting a great education!
RE: switchgear short circuit ratings
RE: switchgear short circuit ratings
www.cbsnuclear.com
RE: switchgear short circuit ratings
RE: switchgear short circuit ratings
You might want to get a copy of A Practical Guide to Short Circuit Calculations by Conrad St. Pierre. He covers all of this in detail.
As I mentioned before, this is not a straightforward calculation.
RE: switchgear short circuit ratings
RE: switchgear short circuit ratings