Bundled Bare Conductor Derating

[TEWISUEE]

I'm trying to determine the ampacity rating of three 1590 AAC in parallel arranged in a flat configuration 2 inches apart. I have calculated the ampacity for a single conductor using the IEEE method and understand how to calculate the proximity effect of the conductors. Is there any additional derating I need to consider? I think to be conservative the amapacity of the two conductors on the leeward side of the first conductor should be calculated with no wind. Would this be a correct assumption?

 

[7anoter4]

Did you followed IEEE Std 738™-2006 IEEE Standard for Calculating the Current-Temperature of Bare Overhead Conductors ?
See ch. 3.4.3 Forced convection heat loss rate
“Equation (3a) applies at low winds but is incorrect at high wind speeds. Equation (3b) applies at high wind
speeds, being incorrect at low wind speeds. At any wind speed, the larger of the two calculated convection
heat loss rates is used.”

 

[TEWISUEE]

Yes, I think these equations are used to obtain the qc1/qc2 value if you are calculating the amapacity of conductor assuming a wind. Equations (5a or 5b) are used to obtain qcn if you are calculating the amapacity assuming no wind, e.g. conductor in a substation surrounded by buildings. I'm wondering what additional derating, beside proximity affect, does one need to consider when calculating the ampacity of three 1590 AAC conductors in parallel. i.e. bundled (same phase). Does one use qc1 or qc2 for one conductor and qcn for the other two OR is there something else that should be used to get the ampacity of each conductor then add those values together to get the amapcity of all three conductors.

 

[7anoter4]

In my opinion, in order to calculate the losses in conductors the following effects you have to consider: conductor resistance-temperature corrected, skin effect, proximity effect, hysteresis and eddy current effects, corona. See: Aluminum Electrical Conductor Handbook.
The solar heating has to be added.
Usually, if the conductors are laid in a horizontal row and the clearance between conductors is more than twice the conductor diameter, no derating is required.

 

[TEWISUEE]

Thanks for the input 7anoter4.