Aluminium Overhead Bare Conductor

[Miguel Villarroel]

Why? in aluminium conductors elastic modulus changes but coefficient of linear expansion doesn´t change, (of course, changes over time)

If there was no electricity there would be no internet. Good point, don´t you?

 

[MikeHalloran]

I don't understand any part of your question. E.g.:
Why overhead?
Why aluminum?
Why bare?
Why does the elastic modulus change with time, but the coefficient of linear expansion doesn't change?

WRT to the last question above, I'd have to reply that the contained assertion is not true. I.e., aluminum in service is subject to strain hardening, which raises the yield point but does not change the elastic modulus nor the coefficient of linear expansion. If you have evidence to the contrary, I'd like to hear about it.

Answers to the first three questions above are all basically economic in nature.



Mike Halloran
Pembroke Pines, FL, USA

 

[jghrist]

For stranded conductors, there is a difference in the modulus of elasticity from initial (before loading) to final (after reaching maximum working stress). The initial modulus is lower because there is initially a slight slack in the individual strands that goes away under loading. The virtual initial modulus of aluminum cable is 7.3 * 10^6 lb/in². The final modulus is 9.1 * 10^6 lb/in².

 

[MikeHalloran]

Thank you for the education, jghrist.
Now the day is a success.


Mike Halloran
Pembroke Pines, FL, USA

 

[Miguel Villarroel]

Good point my friend, but internationally is accepted that after final, modulus of elasticity keep changing over time, my question is: why? it doesn´t happen with coefficient of linear expansion

If there was no electricity there would be no internet. Good point, don´t you?

 

[MikeHalloran]

I though jghrist's explanation, that the >apparent< E goes up with loading and with age, and approaches the measured E of solid wire, as the wires work and relieve initial slack space, was credible.

I suppose the apparent E of a length of stranded wire could also go down, as individual wires break from old age or unreported impact, and as their net cross section is reduced from chafing or corrosion.

... but I'm speculating. Have you got some old wire to test?
Or a way to test it? Or test data?


Mike Halloran
Pembroke Pines, FL, USA

 

[Miguel Villarroel]

Little changes in length are fatal, you know. In this way, i referred to coefficient of expansion 10 years down the road, why i must use same coefficient to study conductor´s behavior but modulus of elasticity changes. I refer the most to overhead distribution where is common using AAC or AAAC conductors to share energy. Best regards.

If there would not electricity, there would not internet