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 !

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?

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.

i think it is not related with form factor as many replied
because if so then why 400 kv or 765 kv is followed as
these r not multiple of 11.i think becuse of constrainst in
gen voltage that is between 10.5 to 15 kv we[earlier]to
choose 11 kv and 33 66 132 kv r multiple of 11 to suite
our transformation ratio.if once follewed it continuied
otherwise i dont find any reason that with 12 kv gen why v
cant have 44 144 kv transmission.

I have 1 KW, 3ph. 440v, 50 hz, cos(phi) .75, efficiency
75%(star delta connection)Motor. How to calculate line
current & Phase current (1) Star connection (2) delta
Connection

Using 11000V/433V,3 ph,50Hz,500 KVA, what is the maximum
capacity of motor in KW that can be connected and started at
a single moment? Also explain about any calculations and
formulas used in deriving the same.