Why electricity is being transmitted in Multiple of 11?

Have you ever wondered? why we use only 11KV / 22KV / 33KV / 66KV / 110KV / 230KV / 440KV which are multiples of 1.11(we can say multiple of 11).We can generate this voltages efficiently because of form factor of sine wave is 1.11.So it is efficient to produce that range of voltages.Form factor is the ratio of RMS value to average value.For a pure sine wave it is around 1.11.
We can't have a combination of other then a multiple of 1.11.
So we can see all the voltages are made inevitably multiple of this value (1.1, which is the form factor of ac wave).Also it provides us the best economic construction of step up and step down transformers.

Right Answer:The answer given above is taken standard electrical book.But that is wrong the actual answer is when we want to maintain 10KV at receiving end, transmission companies transfer 10% extra than receiving end voltage.i.e., 11KV simillary 10% of 20/30/60/100KV gives us 11KV / 22KV / 33KV / 66KV / 110KV respectively.

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