Copper is a good conductor of electricity but we use aluminium as a conductor instead of copper in transmission lines.
In order to investigate whether to use copper or aluminium in transmission lines, we should do comparasion of both including all of its factors.
Aluminum conductivity is very close to that of the copper i.e. about 1.6 times as much resistance per foot for equivalent gauge. So in equivalent wire sizes, aluminum would lose 60% more power to I²R losses. But aluminum has two properties that make it worth using.
In density aluminium is about 1/3 the weight the weight of copper per same volume. So this gives a serious advantage mechanically to aluminium over copper since we can increase the cross section area by 2 (make it 1.414 times the diameter) and also that it will have 0.8 times less the I²R loss of copper and still be 2/3 times the total weight, making the towers cheaper to build because they don’t need to be as strong by a factor of 0.66.
Secondly the cost of copper by weight is around 6 times as much from aluminum. That means even though we used 2/3 the weight above we are still at a 10% cost (0.66 x 1/6) for the wire itself excluding the tower costs savings.
So, we could conclude that:
- We can reduce 20% in resistance and hence I²R power losses from about 6% to 5% and saving 1% of all energy produced and transmitted for years to come.
- We can save 33% in construction costs as tower strength required is less for alumium as the wire is only of 66% of the copper weight.
- We can save as much as 90% of the cost of the wire itself due to material costs.
There are other problems with copper based strand aside from cost and density.
- It’s highly reactive to oxygen and corrosive factors from rain or pollution, placing a protective coating around the copper strands would only serve as a short term stopgap. The coating would wear away and it’s back to square one. Copper’s conductivity is negatively impacted by corrosion.
- It’s not strong enough to be used the way we use aluminum and steel strand now. The lines we use today function as a high tension line that supports more than just its own weight. They serve as a structural support member of all the towers and poles that are keeping it suspended. These lines stay in the air for many years if not decades before they require replacement, copper would necessitate most of the lines in the nation to be replaced every few years or less.