Answer / shahulsnfa

everybody is copying from books and pasting here not even
one answer is practical..

Answer / neel

i can't think so,plz give me rgt ans.

Answer / parmar hitesh

because by some experiments it is proved that the harmonics
influence at this voltage is minimum. so it is selected as
the satandard voltage value and the another point is of ff
which is1.1

Answer / abhijeet

why not in transmission voltage we use 55 77 88

Answer / jayakrishnan

Because the transmission losses will be less in the below voltages as calculated,
11KV
33KV
110KV
230KV
And in 66KV

Answer / venkatesh

we use 11kv 33kv 66kv because form factor of sine wave is1.11 and transformer emf equation should also a reason

Answer / maheswara reddy modugula

Why transmission line 11KV OR 33KV, 66KV not in 10KV 20KV?

1•The miss concept is Line voltage is in multiple of 11 due to Form Factor. The form factor of an alternating current waveform (signal) is the ratio of the RMS (Root Mean Square) value to the average value (mathematical mean of absolute values of all points on the waveform). In case of a sinusoidal wave, the form factor is 1.11.
2.The Main reason is something historical. In olden days when the electricity becomes popular, the people had a misconception that in the transmission line there would be a voltage loss of around 10%. So in order to get 100 at the load point they started sending 110 from supply side. This is the reason. It has nothing to do with form factor (1.11).
3•Nowadays that thought has changed and we are using 400 V instead of 440 V, or 230 V instead of 220 V.
4•Also alternators are now available with terminal voltages from 10.5 kV to 15.5 kV so generation in multiples of 11 does not arise. Now a days when, we have voltage correction systems, power factor improving capacitors, which can boost/correct voltage to desired level, we are using the exact voltages like 400KV in spite of 444KV

Answer / subhash

As per our Indian standard it is derived from the form
factor I quite agrree to this answer because one question
arise why not 22,44,55,77..... & why 400 KV?

Answer / vinod

any one who say that it is due to form factor is incorrect ,
no such reason for this question, at starting addison
produce 110 v dc, and that production nature also follow in
ac system.

Answer / bigwoolleypenguin

The reason for these "odd" voltage figures dates back
years.The original idea was to make up for the voltage drop
in long transmission line conductors , hence 11KV was
designed to deliver 10 KV at the end of the line , 132 KV
was designed to deliver 130KV at the end of the line and so
on. It has nothing to do with form factor . Also this has
long been abandoned and nowadays the voltage supplied at
the end of the line should be the voltage stated plus or
minus a very small percentage. 400 KV voltage appeared
after this idea was abandoned , hence it is a " round "
figure . Otherwise it might have been 405 or 410 KV !

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