ACSR (Aluminium Conductor Steel Reinforced):

ACSR (Aluminium Conductor Steel Reinforced):

Due to low tensile strength, aluminium conductors produce greater sag. This prohibits their use for larger spans and makes them unsuitable for long distance transmission. In order to increase the tensile strength, the aluminium conductor is reinforced with a core of galvanised steel wires. The composite conductor thus obtained is known as steel cored aluminium and is abbreviated as ACSR(aluminium conductor steel reinforced).

Steel-cored aluminium conductor consists of a central core of galvanised steel wires surrounded by a number of aluminium strands. Usually, the diameter of both steel and aluminium wires is the same. The X-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. The figure below shows steel cored aluminium conductor having one steel wire surrounded by six wires of aluminium. The result of this composite conductor is that steel core takes a greater percentage of mechanical strength while aluminium strands carry the bulk of current.

Advantages:
(i) The reinforcement with steel increases the tensile strength but at the same time
keeps the composite conductor light. Therefore, steel cored aluminium conductors will
produce smaller sag and hence longer spans can be used.
(ii) Due to smaller sag with steel cored aluminium conductors, towers of smaller heights
can be used in overhead line design.