Overhead Conductor Ampacities
Overhead Conductor Ampacities
(OP)
Would anyone have the ampacities for 336 & 556 AAC conductors at 90-95 degrees Fahrenheit?
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Overhead Conductor Ampacities
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RE: Overhead Conductor Ampacities
556 KCMILS AAC--680 AMPERES
Per Electrical Engineers Handbook, Thirteenth Edition
RE: Overhead Conductor Ampacities
RE: Overhead Conductor Ampacities
RE: Overhead Conductor Ampacities
dpc
RE: Overhead Conductor Ampacities
RE: Overhead Conductor Ampacities
RE: Overhead Conductor Ampacities
Thanks for being detailed. I should have been more specific.
RE: Overhead Conductor Ampacities
RE: Overhead Conductor Ampacities
RE: Overhead Conductor Ampacities
All the above takes some work to calculate, even more if you are going to account for emergency loading at higher temperatures which will sag your conductor as dpc pointed out, so most people cop out and use a table. The one I have handy (Hubbell/Anderson Technical Data) says 400 A for 336.4 kcmil AAC based on 61% IACS aluminum alloy, average temperature rise 30 C above 40 C ambient, horizontal, 60 Hz, outdoors, 2 fps wind, minimum 18" spacing. No mention of sun or emissivity.
Different tables will be based on different conditions and hence will have different ampacities. I have seen ampacities from tables differ by up to 50%. No offence, but it sounds like you don't have the technical background to come up with a meaningful ampacity number. Better start talking to your distribution engineers.
RE: Overhead Conductor Ampacities
It is published by McGraw-Hill.
There is now a fourteenth edition.
The authors are Donald G. Fink, and H. Wayne Beaty
I also use SynerGEE too. I think it is the best
for mapping, but for one-line analysis, it is pathetic.
RE: Overhead Conductor Ampacities
RE: Overhead Conductor Ampacities
The conductor temperatures are selected based on the clearances between the lines and from ground level.
You basically pick your mounting heights and sags taking into account a worst case ambient temp and the operating conditions you expect on the line.
Sooo, here's some numbers I ran on my OH line ampacity software for the listed conditions.
Conductor: 336.4 Merlin
35 degC (95degF)
2 ft/sec crosswind
3000 ft eleveation
38 degrees latitude
11:00am in sun
440 amps for 75 degC conductor temp
520 amps for 90 degC conductor temp
Conductor: 336.4 Merlin
40 degC (104degF)
2 ft/sec crosswind
3000 ft eleveation
38 degrees latitude
11:00am in sun
406 amps for 75 degC conductor temp
497 amps for 90 degC conductor temp
Without doing a lot of digging for your 556 AAC conductor, I don't know the exact properties, but I have on hand information on 559.5 Aluminum (Codeword Darien), if that is close enough for your needs.
Conductor: 559.5 Darien
35 degC (95degF)
2 ft/sec crosswind
3000 ft eleveation
38 degrees latitude
11:00am in sun
560 amps for 75 degC conductor temp
672 amps for 90 degC conductor temp
Conductor: 559.5 Darien
40 degC (95degF)
2 ft/sec crosswind
3000 ft eleveation
38 degrees latitude
11:00am in sun
516 amps for 75 degC conductor temp
637 amps for 90 degC conductor temp
The software uses the calculation method suggested in IEEE 738-1993. That IEEE standard would be a good reference on OH conductor ampacity if you haven't already looked at it.
Please remember that the ambient conditions are really your ruling factors for conductor ampacity, so you should design for worst case to be safe. Hope this helps a little.
RE: Overhead Conductor Ampacities
RE: Overhead Conductor Ampacities