High voltage pylons carry as much as 400,000 volts to deliver the electricity over long distances.
Then it gets stepped down to lower voltages until it reaches residential areas and the lines going to homes are stepped down to 240 volts which is 120 volts on each wire.
Distribution lines typically carry between 66 kV and 33 kV although smaller distribution lines carry around 13,000 volts or less.
The voltage of distribution lines – the lines many people see in their neighborhoods – is approximately 13 kV (13,000 volts); a typical household runs on 110 volts.
Today, transmission-level voltages are usually considered to be 110 kV and above.
Lower voltages, such as 66 kV and 33 kV, are usually considered sub transmission voltages, but are occasionally used on long lines with light loads.
Voltages less than 33 kV are usually used for distribution.
The reason 11kV 22kV 33kV 66kV 132kV is in India is because initially the initial, engineers considered the 11kV, 22kV, 33kV, 66kV, 120kV etc based on the transmission distances (from generation point to the receiving end) and the system and these level were satisfactory for different transmission distance.
In olden days when the electricity becomes popular, the people had a misconception that in the transmission line there would be a voltage loss of around 10%.
So in order to get 100 at the load point they started sending 110 from supply side.
This is the reason.
It is cheaper to generate at a relatively lower voltage and then step it up for transmission.
Hence, most power generating plants are designed to operate at 11kV.
To generate at 33kV, the size of the motor might be twice as large as the size of 11kV generator.
The 11kV lines are used in residential areas and is what feeds the local transformers, which then distributes power to the buildings in the area.
33kV lines on the other hand involve much higher voltages and are used to distribute power from one small sub-station to another.
22kV can carry twice the load of 22kV.
For two reasons for choosing 11kV over 22kV, one is that protection systems would be cheaper and smaller.
The other is power correction of an 11kV system would require smaller devices as well.
Why do we use AC and not DC system in India?
Simply put, AC voltage is capable of converting voltage levels with just a transformer, making it far easier to transport across great distance than DC, whose conversion requires more complex electronic circuitry.
Electric charge in AC periodically changes direction, causing the voltage level to reverse.
Transmission voltage in India (highest) is 765 kV AC and these lines are erected by Power Grid Corporation for interstate connections throughout India.
DC transmission voltage (highest) in India is 800 kV.
The 33 kv substation systems are distribution substations that take electricity from transmission substations and then supply the same to the end consumers after stepping down the high voltage to a safe level.