why transmission is done at high voltage

 

Why transmission is done at high voltage

     Whenever a transmission  word comes into our mind,the numbers 132 kV,33 kV ,66 kV,etc., floats infront of our eyes. 

       Our household appliances like fan, refrigerator works efficiently on 230 V. Even for industrial purpose, we need 440V (generally). 

      Then why transmission is done at high voltage? What is need of this extra high voltage?

Now friends ,you must know we don't generate high voltage at Generating station. Usually we generate the power of 11 kV voltage.

So friends ,to transmit high voltage there is need of the transformer to convert 11 kV (generating voltage) to higher voltage. Now this is a step up transformer, it is worth a lot. Because of use of transformer, our cost of transmission increases .

Then why we use high voltage for transmission? Is there any advantage ? Let's see .

 Advantages of high line voltage: 

(1)low voltage drop:   

Power is transmitted over large distances to load centers with the help of conductors. We know , resistance increases with increase in length of conductor( prefer formula) .      

  

               R= p l /A                 

Hence, the voltage drop across conductor also increases .

 As transmission line voltage is high , voltage drop across line is decreased.

(2)low cost: 

As we increase /step up voltage by using transformer , current decrease with respect to increase in voltage

 (as per low of energy conservation)

        We know ,   power                         

               P = constant 

    Also , P= V*I

Since current decreases area of material (A) also decreases 

              I = V / R       ....  I α 1/R

             R = p l / A     ....  R α 1/A

Hence,

            I α A 

 

Therefore it requires less material . Effectively low cost of conductors.

(3)less power loss:

Increase in voltage reduces the power loss. As voltage drop is less for high voltage as compared to low voltage ,the power loss decreases and we have better voltage regulation .

 Disadvantages of high line voltage

  From the above discussion, it is advisable to use the highest possible voltage for transmission of power in a bid to save conductor material. However, it must be realised that high transmission voltage results in

(1) The increased cost of insulating conductors : 

      As the voltage tension increases on wire,there is need to increase insulation. But for transmission lines we don't use insulation . 

(2) The increased cost of transformers, switchgear and other terminal apparatus (of high voltage rating)

(3) Tower height increase : in order to minimise line - ground fault . 

(4) Increase corona effect (corona discharge)

 I hope this helps you. Thank you ❤️.