A General Question?

Question:

Why transmission line voltages are used as 11KV, 33KV? Why not 10KV or 30KV-------Give Reason?

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Answer:

When an alternator generates voltage, we always use a multiple of 1.11 because for a pure sine wave the FORM FACTOR is the ratio of rms value of voltage or current with the avg. value of voltage or current and for pure sine wave rms value of current is Imax/root '2' and avg. value is 2Imax/pie and which comes out to be 1.1

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)