Rating of HT System

Please see any of the dozens/hundreds of threads that already exist on this ridiculous question. If you look at your own local standards, you can probably find several voltages that are not divisible by 11.

(There are some "reasons" that are occasionally offered, none of them very convincing.)

Would the same question be asked if they were multiples of 17?

Groan….

It's like toothache it just won't go away!

If we could persuade the PM of India to bump all the voltages up/down by 5%, then MAYBE this goofy idea might finally go away....

Dear Guru Tarnado, can you please explain why to persuade the PM of India on this matter. Why not to President of USA or head of state of any other country?

Most, though not all, askers seem to be from there.

Most, though not all, askers seem to be from there.You don't know from which country OP belongs, but you presumed it. I want to bluntly say that it's wrong and humiliating, you should feel sorry for it. Just few week back there was a thread "Not so many questions", widely commented. Your such comments are one of the reason. Even though there is guideline in CR4, that before posting a question, they should first search it, but many new comers make such mistake. Being a senior member and Guru, you should guide them instead of making sarcastic comments.

Who told you like this ?

Railway voltage standards are different then you have mentioned !

MV systems with 3.3kv / 6.6 kv / 0.86 kv etc... are also found in steel melting furnaces / Water pumping stations etc...

THE MAGIC OF THE MULTIPLES OF 11

Foreword:

The author has been coming across the following question repeatedly from the participants in his training programmes. Many other electrical professionals and electrical engineering students would also be having the same question in their minds, but only hesitant to ask anybody. An attempt is made here by the author to answer this question.

Question: Why Transmission, distribution and utilization voltages are in multiples of 11, as in 110V, 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 be 11kV, 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 about 1.1. 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 of 11.

********

Although this purports to be an explanation, I do not find it convincing in the least.