ALUMINIUM VS. COPPER CONDUCTORS FOR DC SUPPLY

[appunni]

Sir,
In one of our substations, we have to extent 110V dc supply to motor control panels which are 600 meter away. We have 16sq. mm aluminium cable. Can we use it for dc supply extension? Is there any problem in using aluminium cable for this purpose? If copper is to be used what should be its size? I request for your valuable comments. Thanks in advance.
With regards,
Appunni

 

[jghrist]

I would avoid using aluminum in a dc circuit for fear of accelerating any galvanic corrosion in aluminum/copper bimetallic connections. I am by no means an expert in galvanic corrosion, however. I don't really know if my fear is justified, but I personally would spend the extra for copper instead of the time to assure myself that there isn't a problem with aluminum.

As far as the size of copper, you don't give any information necessary for sizing the cable, so I can't comment.

 

[JJMI]

For wire, aluminum has a higher resistance than copper, which means that if aluminum is used over copper, then the wire will be of a lower AWG (thicker wire).

Aluminum also tends to corrode if left bare for a good amount of time, or if it becomes wet. Soldering the wire to the connections would prevent this.

To figure the AWG, many web-sites have wire AWG charts. The wire size depends on the current it will carry.

 

[jbartos]

Suggestion: Visit

http://www.epanorama.net/documents/wiring/wire_resistance.html

http://www.okonite.com/engineering/index.html

http://teacher.nsrl.rochester.edu/phy122/Lecture_Notes/Chapter28/chapter28.html

etc. for more info

 

[hsj]

No problem in using aluminium provided:
- Size selected is adequate for current capacity and voltage drop
- While instaling lug on the cable a special compound is aplied to reduce oxydation. Similarly while terminating a cable same compound is applied to the contact surfaces. I think the compound is petroleum jelly but not sure because not used aluminium cable for a while. But in India aluminium cables are used extensively and no problem if these precautions are taken
- If there is a copper to aluminium termation then either suitable lug(al to copper lug) or a bimetallic strip is used.