In comparing the aluminum conductor and the copper conductor cable, the copper was always a better conductor but what about the high voltage power transmission used in underground, can it beat the copper? Which one will be the winner? In this article we will discuss this matter.
High Voltage Aluminum Cable
The electrification of the world is being facilitated in large part by the installation of electricity cables buried underground.
Copper's high conductivity would seem to make it the material of choice for the conductor, therefore it's not surprising that it is.
On the other hand, this is not always the case.
When a thorough life cycle analysis (LCA) is performed, the experience gained from France's transmission grid has demonstrated that aluminum may on occasion prove to be the preferable choice.
When deciding on a conductor for an underground cable system, there are a lot of different factors that need to be taken into consideration.
Considerations pertaining to electricity, thermal design, methods of installation, mechanical tensions, and so on are some examples of these.
ELECTRICAL RESISTANCE
Because of their high conductivity, copper (Cu) and aluminum (Al) are the only two metals that are utilized in the production of underground cables.
Silver is the best metal for conducting electricity, despite popular belief to the contrary.
Unpredictably, gold comes in at the third spot, right after copper, with aluminum coming in at the fourth spot.
Copper has an electrical conductivity that is significantly higher than that of aluminum by a factor of 1.64.
However, it is over three times heavier and has a significantly higher price tag.
Copper prices are subject to significant swings; yet, there have been periods in this century when the price of copper was five times higher than the price of aluminum.
Because of these considerations, a conductor made of aluminum must be larger in order to carry the same amount of current as one made of copper.
Despite this, the aluminum cable can be purchased at a lower cost and is easier to work with than copper cable.
A few modifications are available, such as enamelled copper wiring (CUE) or oxidized aluminum wires.
EXPERIENCE WORKING ON THE GRID IN FRANCE
It is interesting to keep track of how each conductor performs in comparison to the others.
One illustration shows that a 2500 sqmm Al cable has a rating that is very near to the same as a 2000 sqmm Cu cable.
The conductor accounts for the majority of the energy that is lost in an underground cable due to losses.
The typical cumulative losses suffered by cables after installation in France, expressed as a function of the current rating of the cables.
The curves terminate at the steady-state permitted current rating, which is associated with the highest temperature that the insulation material can withstand (for XLPE, which stands for cross-linked polyethylene, this temperature is 90 degrees Celsius).
The magnitude is equal to 30 Watts per meter of cable.
High Voltage Aluminum Cable Best
The French transmission system operator, Réseau de Transport d'Electricité (RTE), has produced statistics showing that underground cable systems operate more than 95% of the time at a current rating that is lower than 60% of their maximum rating.
These statistics can be found in the article "Transmission System Statistics."
This indicates that the losses are often a significant amount lower than their highest potential worth.
The remaining 5% of the running time corresponds with the peak values and conditions that are the most restrictive, such as when there is a particularly harsh winter and a significant amount of electrical heating is used.
The conclusion that can be drawn from this is that the operating circumstances of an underground cable are typically those that result in "acceptable" losses.
