Power Generation in India

Thats a billion $ question yet to be answered on CR4. or anywhere else, I am sure someone in our bureaucracy will answer it correctly, You should file a an RTI application.so that you can get an answer in quick 11 Weeks. Otherwise I am sure it will take you 11years to get an answer from Them.

RTI - Right to informations

I always felt that this was done just to automatically imply a ±5% tolerance window by picking nominal multiples of 11 (11±0.5).

Back in the sands of time, there once was a shadowy Committee of Eleven who selected the voltages for India. It's probably written in the Rig Veda somewhere....

Some sources show 230/1 and 240Y/415Δ/3 as voltages in India. None of these numbers is divisible by 11.

Originally it was 220 and 440 Volts in LT ( later changed to 230 and 240 ),3.3 KV, 11kV ,22kV, 33kV ,110kV ,220 kV and now it is 400kV lately. The Electrical System in India was developed during British rule and all the systems followed in UK was brought to India. So the system followed there had to be followed as all of the voltage system followed in UK was adopted and as the equipments produced there were brought from there. The system had to be continued after Independence and even now continuing here with certain changes to convenience of the local conditions( like voltage drop due to long distribution lines) and other design factors.

The equipment rating of 240 kV is used for 230 kV substations , to ensure safety of equipments considering voltage fluctuations. Nominal kV is 230 kV, Rated kV is 240 kV.

Normally in distribution network the LV side is rated higher than the nominal kV to act as a correction for voltage drop due to loads.

What's so special about 11 (apart from it being the maximum volume setting on a Marshall electric guitar amplifier, that is)?

http://cr4.globalspec.com/search/sitesearch?do=show&sort=textmatchrank&srch=why%2011%3F&order=asc

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.

********

thanking u sir

This seems confused, and is unconvincing. Though I'm not sure, I would call it a pseudo-explanation (or a "just so" story).

In the beginning, electrical generation and distribution was in DC due to first electrical machine was invented in DC. So distribution or transmission was in 10KV DC only.

After some time later, induction machine was invented and become more popular and most useful. Therefore, it was required to transmit AC power to long distance. To minimize the cost, it was thought to use same DC transmission structure such as poles & 10KV insulators.

Question arise was what maximum voltage rating of AC can safely be applied on the same DC 10KV insulators.

The following calculations give the answer:

Assumed the AC Voltage is represented by a sin wave form of Vpsin(wt).

The average voltage (DC) over half cycle or quarter cycle of the sin wave form is 2*Vp/PI

Where PI = 22/7

The R.M.S voltage of the same wave form is Vp / √2

The ratio of the R.M.S value/Average Value = (Vp /√2)/ (2*Vp/PI) = PI/(2*√2)=1.11

This ratio is nothing but Form factor =1.11

AC voltage is estimated from the Form factor as R.M.S value/Average Value (DC) =1.11

R.M.S value =1.11 * Average value (DC) = 1.11*10KV = 11.1 KV

Therefore, DC 10KV rated one insulator can withstand 11KV AC Voltage without insulation breakdown.

Hence, 11KV AC generation, and distribution stared from then onward.

After inventing of transformer, transmission was started 22KV (using two insulators), 33KV (by three insulators), 66KV (by six insulators) and so on so forth.

The 11KV is used in 50Hz supply and the countries adopted this supply Voltage are Europe and most of the Asian countries including INDIA as well.

However USA and some countries are using power supply of 13.8KV & 60Hz. Their power generation and transmission could be due to the following reason:

V(USA) = V(Europe)*60Hz/50Hz = 11.1KV *1.2 =13.32, so they use 13.8KV

Mushtaq Hussain-INDIA

thanking u sir

That is very muddled.

Pi ≠ 22/7 (though 22/7 is close and misleadingly introduces a multiple of 11).

If there is a form factor of 1.11, then voltages should be multiples of 111, not 11.

Etc.

It was rounded the voltage from 11.1KV to 11KV for convenience. So it was started generation of AC power at 11KV.