2500A Round Copper Bus 1

[flyboyz]

Hi all,

I have an outdoor metal-clad switchgear application at 34.5kV, 2500A that required the use of hollow round copper bus. Outdoor condition is hot and high humidity.

A 1/4 x 6'' flat bar rated 2700 A @ 65 deg C rise was the guideline according to this Copper.org website.

http://www.copper.org/applications/busbar/ampacity/busT1.htm

If I take the flat bar cross section and applied the equvalent cross section to the round copper bar, is it going to be valid? Say, a 2'' diameter with 0.5'' outer wall thickness?

Also, does heat shrinking the bus derate the temp rating hence the ampacity?

Any feedback will be very much appreciated.
Thanks in advance.

 

[jbartos]

Suggestion: Tubular copper bus has imbedded advantages over rectangular cross-section bus, namely: Skin effect phenomena is resolved, it can be cooled (Incidentally, is the tubular bus cooled internally?), etc.
The rectangular bus should have the ampacity rating the same of higher than the tubular copper bus. It may be a good idea to adhere to industry standards for bus applications, e.g. IEEE Std 605:

http://standards.ieee.org/catalog/olis/subst.html

http://standards.ieee.org/reading/ieee/updates/errata/605-1998_errata.pdf

 

[alehman]

A tube of equivelant wall thickness will have less capacity becuase effectively only one side is exposed to ambient air (unless you force air through the tube). Also, heat radiated from the interior surface will be re-absorbed rather than dissipated. The skin effect should be roughly the same if the thickness is the same as the bar.

You should probably consult the copper supplier for specifics on the exact material being furnished.

 

[BJC]

I've posted this before, It's worth downloading and saving on disk. See table 13 on page 10..

http://www.hubbellpowersystems.com/powertest/catalog_sections/Technical_Data.pdf

 

[flyboyz]

Thanks again for all your feedback and references.

 

[jbartos]

Comment on BJC (Electrical) Mar 22, 2004
I've posted this before, It's worth downloading and saving on disk. See table 13 on page 10..
///The link does not appear to be working.\\\

 

[BJC]

Worked for me just now. Different computer but all 96 pages came up.

Try Google searching for "Hubbell Power Systems Anderson Electric"
It's the first hit I get, then go to catalogs, then refernece data. It's number 6 on the list.

 

[tulum]

worked for me as well

 

[jbartos]

I beg your pardon. The link works. File is about 5.3MB.
More comment from current Fink, Beaty "Standard Handbook for Electrical Engineers":
Tubular conductors used on alternating current have a better current distribution than any other shape of conductor of similar cross-sectional area, but they also have a relatively small surface area for dissipating heat losses. These two factors must be balanced properly in the design of a tubular bus. Tubing provides a relatively large cross-sectional area in minimum space and has the maximum structural strength for equivalent cross-sectional area, permitting longer distances between supports. In outdoor substations, spans up to 40 or 50 ft with 6-in-diameter copper or aluminum tubes are considered practicable. ....
Current rating tables are included therein.