OVER HEAD LINE CONDUCTORS

The material which is used for the construction of line conductors is known as overhead line conductor e.g cu.aluminium steel and alloy
Types of conductors 
Different types of conductors are in use for manufacturing of line conductors some of them are listed below
1.solid conductors
2.hollow conductors
3.stranded conductors
4.Expanded conductors
5.Aluminium conductor steel reinforced
Now a days which material and type is widely in use they are discussed below
Stranded copper conductor

Copper is the ideal choice for overhead line due to its electrical conductivity and tensile strength ,its current density is also high so loss cross section area conductors will be required , copper conductors are also known as homogeneous conductors because they are made of same material
The advantages of copper wire are:-
1. They high enough strength no need of steel reinforcement
2.These conductors are flexible
3.Long transmission can be made of copper
4.Transportation is easy
The only disadvantage is its cost
Hollow copper conductor 

Instead of solid conductors which are already shown in the figure hollow conductors are in use now a days in the world the main reason behind the use of these conductors are :-
1.Its decrease copper losses
2.decrease corona losses
3.It decrease the skin effect
For decrease in corona bundle conductors are also use
As we know by increasing the voltage on line it will effect the spacing between line (which will be increase) so as a result the length of cross arms of tower will also be increased so in this condition hollow conductors are use hollow conductors can be use for Ehv also
Aluminium conductor steel reinforced 

In stranded aluminium steel is reinforced this type of conductors is known as ACSR in figure Fir line is ACSR while the second one is expanded conductor which will be discussed later in this topic

Now a day ACSR is widely use in transmission line due to its low cost its conductivity and tensile strength is less than copper but still it is first choice for transmission line due to low cost .As it have low conductivity so its diameter will be higher than copper wire the increased in diameter has one  advantgae and two disadvantges, the advantage is

1.corona effect will be decrease

 The disadvantages are 

1.Wind pressre will be increased 

2.sag will be increased 

3.Conductor will also be increased 

Why steel reinforced in AL line

The reason behind steel reinforcement is as the tensile strength of AL is less than CU while the Tensile strength of steel is higher than cu so to increase the tensile strength of AL wire Steel is reinforced 

In many cases AW (Aluminium weld) is also used AW is a process in which Aluminum layer is weld on steel .AW used where their is higher chances of corrosion 

Cable used in Pakistan

 

In figure 2nd line represents expanded conductor In expanded conductor stranded steel is use instead of solid steel The reason behind this is its tensile strength and its life increased by using stranded steel instead of solid steel