Frequency change?

Normally, in India we use only 50 hertz frequency for the power transmission and distribution purposes. Is This a fixed value? Or what can't we use 60 hertz or the other value of the frequency?
Why it has only been selected from the past?

Simply 50 Hz was picked in India. Many countries picked 60 Hz. In the same way different voltages were picked, from around 120VAC or around 240VAC. These were somewhat arbitrary, and there was no international standard so each country or area did what it thought best. Once it was chosen the generation equipment and the devices that use it are designed for it so it's next to impossible to change it now. Any simple clock that runs on 50 Hz would run fast on 60 Hz.

Here is a link for interesting reasons on why there is no rhyme or reason for the frequencies we use.

http://en.wikipedia.org/wiki/Utility_frequency

We have this relation,
P á (Hz)3
i.e power is directly proportional to the frequency of operation.
This example may clear your doubt,
If a motor power (P1) is 100kW at 50Hz means the power (P2) on the motor at
49Hz would be as follows:
P2 = (49 /50)3x 100
= 0.9412 x 100
= 94.12kW
Therefore the % reduction in power is = 5.88%
It clearly indicates that by reducing the frequency there will be a reduction in
power which intern reduce the energy (kWh) and its cost.
It may also be noted that Hz á rpm.
It also clearly indicates that though there is
a saving in energy at less frequency, there is a reduction in production because
of reduction in motor speed.

If I choose 60 hertz frequency or greater than that ,so that the power produced is more no?

power consumed will be more according to the frequency-power relation. The output depends on the load, i have given you an example of motor.