Why the electrical power can be measured in multiple of 11?

Good question. Answer can be generic and technical.

Generally it is done for easier math.

Mathematically if you see the formula for FORM Factor you'll come to know why it is multiple of11.

Thanks

Question: Why Transmission, distribution and utilization voltages are in multiples of11, as in110V,220V,440V,1.1kV,3.3kV,6.6kV,11kV,22kV,33kV,66kV,110kV,132kV &220kV?Answer: It is true only with respect to AC power systems. The first known man-made source of electricity is a cell, which is DC in nature. But, after realizing the disadvantages of the DC electric equipments, AC Electricity generating machines were invented. When these AC Machines were developed, the power of these machines was to be compared with the already available DC electricity, as it is human tendency to compare anything new with the existing ones. As in the case of steam engines.When steam engines were invented, the power of the steam engines was compared with that of the horses, which were the power sources before the invention of the steam engine.So, a value called RMS Value for AC Electricity was derived which compared the effectiveness of the AC Electricity with that of the DC Electricity. This value is the Effective Value of AC Electricity. As we were more interested in knowing the effect of AC electricity, all measuring instruments were and are designed to measure only the RMS value of AC electricity – may it be Voltage, Current, Power, etc.But, for the designer sitting in the design lab, more than the effective value, the average value over a period on one sinusoidal cycle of AC Electricity was important. So, he designed an AC electric Generator, which would produce, on an average, a voltage over a period of one cycle, of say,10kV (10 is a round figure, you know).But, when this machine was built to the design and put to operation and when the output voltage was measured, it was found to be11kV, as the meter was measuring NOT the average value but the effective or the RMS value. This relation existed for any voltage. So, a factor was arrived at – relating the RMS value and the average value, called Form Factor, which is the ratio of RMS value to the Average value, which for a sinusoidal wave form was about1.1. Then, when the voltage was to be transformed, it was easy to have a whole number for the turns ratio of the transformer and hence all subsequent AC voltages became multiples of11.

it is not correct we are also having electrical power  inkvkv form which in't the multiple of .

I haven't seen any documentation, but I would speculate that the original goals were to provide distribution organizations with simple multiples of in designing their distribution sub-grids. Multiples of would provide for multiples of in distribution voltages after allowing for% losses in the transformers and wires. Now that transformer and line efficiencies run around2.5% rather than% they deliver the nominal excess to the customer rather than re-structure their entire transmission and generation system. The issue even shows up in large industrial plants, where a supply network may be said to operate "nominally" at volts at the transformer while the motors connected to it may be rated "nominally" at volts, or in Canada volts and volts. The intention is to provide for voltage drop in the resistance of the switches, fuses and wiring which feed the motor. It is the job of the plant electrical engineer to decide what actual supply voltage he wants from the utility service transformers by adjusting the transformers tap changers, which can change the real voltage coming off the service transformers according to the engineers decisions on how to balance energy losses, feeder and motor overheating, voltage fluctuations in utility supply, and risk of burnouts due to overvoltage.

yes sir exactly it is right Based on Form factor of power we calculated this11 multiple