aluminium is more expensive then iron . why is aluminium not iron used for the central core in power cables ?

Question

i need to know for a practice exam paper im having trouble with

Answer 1

Aluminium is used due to the weight of the cables, cause steel have a density of 7.8 g/cm³, instead of this Al have only 2.7 g/cm³. So you can have a lightweight construction for the power poles.

The main reason is the electrical conductivity, this is for steel 9.3 * 10^6 S/m. For Al it's 37.7 * 10^6 S/m. The power cables have a lower electrical resistance, which leads to lower losses of energy and lower warming up of the power cables.

Answer 2

Eventually its all about money.

Aluminium is a better conductor of electricity than Iron, and thats the reason it is used in preference to it. For example, it would cost no more to lay an Aluminium Cable, Copper Cable or Iron cable in the ground. On overhead lines Aluminium is used because of its weight but most cables are burried.

So how does it cost less when the materials are more expensive?
Mainly the cable looses volts along its length and the higher its resistance it then the lower the volts are at the end of it. To keep the end users volts high enough you need shorter cables from the substations with a higher resistance cable (like Iron), and so you need many more substations. At a cost of over £100,000 each building a substation far outweighs the extra cost of Aluminium over Iron. Also, when laying a cable in a trench the main cost is actually the civil works of digging the trench (cable at say £45 a meter, and civil works at maybe £100 a meter - quite a difference)

There is a small consideration with the electrical resistance in the Iron. This means iron looses more energy per kilometer than an Aluminium or Copper, and this energy costs money to produce so there are savings there.


Anyway, its all down to the cost of making the distribution network rather than say the weight of the cables.

Answer 3

Two factors: density of Fe/Al= about 3:1. The same length and cross section of Al cable would have 1/3 the mass, adding to its cost effectiveness. Also resistance: aluminium for the same cross section and length has 1/4 the resistance of Iron. Power loss in transmission lines is proportional to the square of resistance, so for the same length and thickness the power loss is (1/4)^2=1/16. Of course if you used superconducting underground cables with appropriate em shielding, transmission could be even cheaper without the attendant risk of em polarisation attracting radon particles increasing the risk of leukaemia in the vicinity.

Answer 4

Iron is too heavy and it rusts. Aluminium is light and although it does corrode, it only does so on the outside. Iron will rust right through, aluminium just gains an aluminium oxide layer which makes it stronger.

The reason why aluminium is so expensive is due to the extraction process. Aluminium requires electrolysis to extract it from its ore while iron requires less energetic means of extraction. This electrolysis extraction process also proves aluminium to be a very good conductor of electricity. Iron is a lot denser so it doesn't conduct quite so well.

Answer 5

I'd agree that the mass of the cable and the resistance to corrosion are both probable reasons. Another might be the difference in the conductivity of the two metals. I don't know which metal has a greater resistance, but I'd guess that iron does.

This is just a guess....

Answer 6

Aluminium is no doubt more expensive than iron but is far more electrically conductive. Iron is a relatively poor conductor. It is also much lighter and thus will reduce the weight of the conductor. Copper is another good conductor but is quite heavy.

Answer 7

I believe weight has something to do with it, also there is the matter of durability and maintenance costs, aluminium is less susceptible to environmental conditions than iron.

Answer 8

First, aluminum is more expensive [than] iron. "Then" is not correct in that sentence.

It's lighter, a better conductor, and more ductile (easily drawn into wires) than iron. These factors make it a much better choice than iron for power cable cores.

Answer 9

well they both conduct electric, so there must be a good reason why, I suppose you mean the overhead power lines? Maybe it is bcoz that Iron is way heavy, so is copper for that matter.


will that do?

Answer 10

Copper is used in most types of cables because its a good conductor and its cheap.

Aluminium is used on overhead cables because it has a lower resistance than copper. And because of the great length of mains cables this is important to reduce voltage drop.