Coodination Study on a PLC Control Panel

[RRoc]

I have never been asked to do a coordination study on my PLC Control panel.
I'm using various amperage of the same Allen Bradley Breakers
1489-A1D020 - 2 Amp
1489-A1D030 - 3 Amp
1489-A1D050 - 5 Amp
1489-A1D200 - 20 Amp

These breakers feed power to I/O module,Power Supplies, and various transmitters in the field (Ultra Sonics, Flow Meters, Gas Analyzer).

The Engineer reviewing my Panel Drawings is requesting a coordination study for the breakers and main breaker in my panel that gets power from the distribution panel.

I would believe if a fault (Line-Ground) were to occur the branch circuit breaker that is experiencing the fault would trip first. None of these breakers have adjustable trip curves.

My response for the my Main breaker to the distribution panel would be for the Arc Flash firm who is doing all the calculation on new equipment.

Do these response have a case?

 

[petersonra]

I think there's a good chance that the trip curve on all of these Breakers is basically the same so if you're expecting a lower rated one of these protected by a higher-rated one to trip in any predictable order I think you are sadly mistaken.

If you are hoping that these 1489 Breakers will trip before the breaker feeding the panel trips you will have to look at the trip curve for the breaker feeding a panel and compare it to the trip curve of these Breakers. If I recall correctly the D in the part number means that instead of a standard trip it is a higher trip like 12 times the rating of the breaker.

 

[Ingenieur]

it all depends on the magnitude of the fault
does the 20 feed the 2, 3 and 5?
page 7 has the curve(s) http://literature.rockwellautomation.com/idc/groups/literature/documents/sg/1489-sg001_-en-p.pdf

the 2 and 3 should go first, the 5 may be iffy
again, depends on the |I fault|
this will be hard to estimate since you need the max current the xfmrs and DC power supplies can supply, and the impedance of the circuits
but you can try to do it for each CB, min and max available, but might be a pita for so many circuits

I might try this
first the ratios are good (20/2 =10, 20/3 ~7, and 20/5 =4, should provide some inherent coordination
if that doesn't fly assume some fault currents and plot them on the curves, estimate voltage/wire Z for a few circuits

or run a test
put the 20 and 2 in series feed from the power supply, and short the 2's at its terminals, and again with a representative length of wire or resistor, this might be the easiest
or test with a multi-amp current source: set various currents and trip, start low and work high, see when only the lower CB goes and when they both go