EuroWire January 2023

Technical Article

Copper and aluminium power cables: cost-benefit analysis By Nagi Ahmed Nagi Abdulmagid, technical manager, alfanar cables company

Copper conductors Copper is one of the oldest known materials. Its ductility and electrical conductivity were exploited by the early experimenters with electricity, such as Benjamin Franklin and Michael Faraday. Copper was the conductor used in inventions such as the telegraph, the telephone and the electric motor. As mentioned above, except for silver, copper is the most common conductive metal and has become the international standard. The International Annealed Copper Standard (IACS) was adopted in 1913 to compare the conductivity of other metals to copper. According to this standard, commercially pure annealed copper has a conductivity of 100 per cent IACS. Commercially pure copper produced today may have higher IACS conductivity values, as processing technology has improved over time. In addition to copper’s superior conductivity, the metal contains great tensile strength, thermal conductivity and thermal expansion properties. Annealed copper wire used for electrical purposes meets the requirements of the ASTM B3 specification for soft or annealed copper wire. Aluminium conductors Even though copper has a long history as the material of choice for conducting electricity, aluminium has certain advantages that make it attractive for specific applications. Aluminium has 61 per cent of the conductivity of copper but has only 30 per cent of the weight. That means that a bare wire of aluminium weighs half as much as a bare wire of copper that has the same electrical resistance. Aluminium is generally less expensive when compared to copper conductors. In the 1960s and 1970s, due to the high price of copper relative to aluminium, aluminium began to be popularly used for household wiring.

Electrical conductivity is the measured amount of current generation created on a metal target’s surface. More simply, it is how easily an electrical current can flow through a metal. While all metals can conduct electricity, certain metals are more commonly used due to being highly conductive. The most com- mon are copper and aluminium. Conductors have different properties, such as conductivity, tensile strength, weight and environmental exposure. Copper and aluminium are not even the most conductive metals, despite being used in many common applications. Another common misconception is that pure gold is the best conductor of electricity. While gold does have a relatively high conductive rating, it is less conductive than copper and nearly down to the aluminium conductivity level, but its cost is much greater. While pure silver is the higher conductive metal, it can tarnish. This issue can cause problems in applications where skin effect is important, such as with high frequency currents. It is also more expensive than copper and the slight increase in conductivity is not worth the added cost.

Material IACS (International Annealed Copper Standard)

Ranking

Metal

Per cent conductivity *

1

Silver (pure)

105

2

Copper *

100

3

Gold (pure)

70

4

Aluminium

61

5

Brass

28

6

Zinc

27

7

Nickel

22

8

Iron (pure)

17

9

Tin

15

10

Phosphor bronze

15

11

Steel (including stainless)

3-15

12

Lead (pure)

7

13 7 * Conductivity ratings are expressed as a relative measurement to copper. A 100 per cent rating does not indicate zero resistance Nickel aluminium bronze

Figure 1 : Development of worldwide primary aluminium production

Demand in millions of tons/year

Year

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January 2023