Why transmission lines are not insulated?

 Why transmission lines are not insulated?

To answer the question, we first overlook the benefits of

 insulation .

Insulation : 

It is the process in which wire is covered by an insulated material (bad Conductor of electricity) 

 Let's see why there is advantages insulation.

There are various reasons for providing insulation:

   (1) leakage current 

If wires are connected to ground then there is  flow of leakage current .To avoid this we give insulation to the wire 

   (2) to separate two  different conductors :

 If two different conductors ( or two different phase )

 comes in contact with each other there is chances for an accidents(short circuit)

   (3) to protect it from environment : 

There are some moisture content in air /environment

 which will damage the wire by producing rust on it.

   (4) protection against electrical shock :

If human or animal touches the live wires there are major chances for electrical shock sometimes   death also.  

  For protection purpose we use insulation.

   (5) mechanical strength:

Insulation provides mechanical strength to the wires .

Instead of so many advantages we don't use insulated lines for transmission. If we look over the transmission lines we will find that:

  (1) leakage current: 

As transmission lines and ground are not connected , since transmission.  

lines are fixed with high height from the ground,the leakage current will not produce . 

   (2) to separate two different conductors : 

Already the two  transmission lines (phases)

 are separated by a definite distance there is no need for insulation.

   (3) to protect it from environment :

Transmission lines are made up of ACSR (Aluminium

 Conductor Steel Reinforced). And aluminium resist rusting .

   (4) protection against electrical shock :

As the height of transmission tower and transmission line is very high such that

 human or animals can't reach so there is no chances for accidents.

   (5) mechanical strength: 

ACSR is a material having high mechanical strength .

Advantages of non-insulated transmission line: 

(1) low cost : 

     (I) for high voltage by transmission line there is need of  high insulation  

     (II) As insulation increases weight of lines also increases  . Therefore ,   tower cost  also increase.

(2) heat protection

       As transmission line are open there is direct contact between line and air .Due to this heated wire cools down easily. 

I hope this helps you. Thank you ❤️.