It is easy to see that this distribution voltage is a multiple of 11 or multiplied by a factor of 1.1. Many argue that the form factor of AC is a reason.

Since the commonly used AC waveform is a sine shape, the form factor is calculated by the formula and it is ~1.11, meaning the actual load voltage must multiply the apparent load voltage by a factor of 1.11. For example:

- 10kV → 10 x 1.11 = 11.1 kV

- 20kV → 20 x 1.11 = 22.2 kV

- 60kV → 60 x 1.11 = 66.6 kV