why power generating voltage is always 11 kV?। generating voltage

why power generating voltage is always 11 kV?

The today's blog is about why power generating voltage is always 11 kV ? Means that whatever power we generate in our power station, why is it always 11 kV only?

   You must have heard this 11 kV voltage i.e. 11000 V many times, whenever we talk about how much voltage is being generated in this power station, then at that time we always take the name of 11 kV. 

So now the question comes that why 11 kV only? Why not more or less than this? 

So friends, it is not always fixed that our electricity can be generated on 11kV only. If you go to all the power plants and see, you will see power generation happening there even at 25 kV, 20 kV voltage. But in most of the cases you see only 11 kV generating voltage.

 There are chances of going to ask this question in an electrical interview. So what is the correct answer after all? Let us see. 

       The answer is that in order to make our system "economical", it means that we can take maximum output and efficiency by investing minimum money in our power plant. 

But here comes another question that whatever is our electricity, we have made 11 kV.Now after this, the power we have generated, we transfer this power from the power station to the substation.We use transmission lines to transfer to the substation. If the voltage of your transmission lines is not 11 kV. They are on our 400 kV or 220 kV means very high voltage.

      So the question arises that if we had to send such high voltage in the transmission line, then why are we generating 11 kV in the power station? Why not generate in direct high voltage only?

        By doing this we do not need a transformer to convert 11 kV to higher voltage. Now friends, this is a step up transformer, it is worth a lot. Now because of using 11 kV, we have to pay a different price for the transformer as well. 

 

        So this question must be coming in our mind that, how 11 kV generated voltage system becomes economical?

So friends, you must know that we use high voltage transmission line to reduce losses in transmission line.

Our 11 kV generator is of very large size. So if we make a generator of 40000V, its size will be very big. 

Now on increasing the voltage, why does the size of the generator increase? There are many reasons for this.

(1) winding turns are increased :

      Whenever we increase the voltage, the turns of our armature winding also increase.

Due to this the size increases.

(2) Increase in insulation :

You would know that if we have any high voltage machine, then the amount of insulation inside it also has to be given more.

If the generator will be so big, then the size of its rotor will also increase. More mechanical energy will have to be given to spin that big turbine.

With the increase in mechanical energy, the amount and cost of the source that generates mechanical energy also increases a lot. 

That's why we considered it right to do power generation under 11 kV by not selecting high voltage and considering 11 kV as standard.

But why only 11 kV? Why not less than 11 kV 4-5-6 kV? If we use them then our cost will be further reduced.

 The correct answer is, whenever we increase the voltage, the value of our current decreases. But if we decrease the voltage then the value of current will increase.

P = V * I

But if the value of current increases, then the size of the conductor carrying it will also increase. Due to increase in armature conductor, our rotor will become heavy. It will take high mechanical power to rotate it. Again our derived cost will increase.

And because the conductor is thick, it becomes difficult to give cooling to it.

To avoid all these things, we needed such a ratio which is economical and our overall power system gives more output with less input. That's why we chose a standard value of 11 kV as the generating voltage.

I hope this helps you. Thank you ❤️.