Transmission Lines Conductor Materials

The question is Why Aluminium Conductor Steel Reinforced (ACSR) is used in Transmission Lines ?

I will go through series of 6-steps to clear this concept

1. Characteristics for a Good Conductor:

a. Low Cost

b.High Tensile Strength

c.High Electrical Conductivity

a. Low Specific gravity (So that weight per volume is small)

2. Characteristics of Copper as Conductor:

a.High Tensile Strength

b.High Electrical Conductivity

3. Characteristics of Aluminum as Conductor:

a.Low Cost

b.Low Specific Gravity

4. When Copper is used in the Transmission Line:

a.Due to High Conducitivity small Cross sectional area of conductor

b.Wind Load will be reduced due to Small Cross Sectional area

c.Due to High Specific Gravity, Strong supporting structure is required

c.Very Costly

5. When Aluminium is used in the Transmission Line:

a.Due to Low Conductivity (60 % of Copper), Large Cross sectional area for Concuctor is required (1.26 times of copper)

b.Wind Load will be high due to Large Cross Sectional area

c.Due to Low Specific Gravity (2.71 gm/cc instead of 8.9 gm/cc of copper), less Strong supporting structure is required as compared to copper

d.Being Light (approximately half the weight of copper) liable to greater swing and hence large crosss arms are required

e. Have greater Sag due to Low Tensile strength and higher Cofficient of Liner Expansion, therefore Tall supporting structure are required

f.Very Cheap

6. Use of Aluminium Conductor Steel Reinforced (ACSR) in the Transmission Line:

Low Tensile strength results greater sag, prohibit to use for large spans and make it unsuitable for long distance transmission Lines. To over come this problem, the aluminum conductor is reinforced with a core of galvanized steel wires. The composite conductor thus obtained is known as steel cored aluminum and is abbreviated as A.C.S.R. (aluminum conductor steel reinforced). Steel-cored aluminum conductor consists of central core of galvanized steel wires surrounded by a number o aluminum strands. Usually, diameter of both steel and aluminum wires is the same. The Cross-section of the two metals are generally in the ratio of 1 : 6 but can be modified to 1 : 4 in order to get more tensile strength for the conductor.

Advantages of ACSR:

a.Tensile strength has increased but at the same time composit material is light. As a result we have smaller sag and can be used for large spans

b.Smaller sag results in the use of smaller height Towers

Hoping this would help

Thanks and Kind Regards

Aghvel Niazi