Why should we generate voltage at certain level and then, only be transmitted? What's the minimum generated

Answer 1

Well batman, it's a little thing people in the industry like to call economics. It's cheaper to transmit higher voltages and step it down as needed.

Answer 2

If your question is:

why do we transmit electrical power at a much higher voltage than we use it?

The answer is rightfully for economic purposes. But to complete the picture consider this:

Ohm's law: V = R * I
Power: P = V * I

As you can see to transmit a unit of power, you can either increase the current I and decrease the voltage V, or increase the voltage V and decrease the current.

Now this unit of power is distributed from the producer (e.g. hydro-electric damn) to the consumer (e.g. you) through very long distribution cables which sometimes span hundreds or thousands of kilometers. These cables have a resistance R which is obviously dependent on distance (the longer the cable, the higher its resistance). The effect of the resistance is to drop the voltage accross the length of the cable. So you might start at the damn with 1000 volts and end at the consumer at 500 volts. WHen that happened you have lost half of your power heating up the cables. How can this be mitigated?

The voltage drop along the cable is given by Ohm's Law: V = RI. In other words the voltage drop V is proportional to the resistance of the cable R and the intensity of the current I. Since your cable resistance is fixed, there is no way to change it. But you can change the current I by raising the voltage.

Example:

A plant produces electricity and distributes it to you. The voltage at your home is 120 Volts AC. The cable resistance is 100 Ohms and you are pulling 120 Watts of power. What is the voltage required at the plant and efficiency of the distribution system?

P = V I
120 W = 120 V * I
I = 1 Amp

so 1 amp of current is drawn. The losses on the line are equal to

V=RI = 100 ohm * 1 amp= 100 volts

So the cable is squandering 100 volts (time 1 amp = 100 watts) of power to deliver you 120 volts (120 Watts). This means the voltage required at the plant is 220 volts and the efficiency os 120 watts consumed / 120 watts produced = 55%. Not very economical is it.

Now let's say the plant delivers this power at 120 000 Volts through the use of step-up and step-down transformers.

The current is now

P = V I
120 W = 120 000 V * I
I = 0.001 Amp

The losses on the line are equal to

V=RI = 100 ohm * 0.001 amp= 0.1 volts
which compared to 120 000 volts is negligible. Efficiency is closed to 100% and everybody is happy.

Answer 3

Higher the voltage, less is the transmission loss ( power loss happens due to resistance of transmission line which decreases with increase in voltage) and smaller crossection of transmission wire which reduces the cost of conductor material.
We do generation generally at 11KV and ste it up to much higher voltage like 66kv or 132kv or 400kv and reduce it again at subscriber end. We do not do generation at much higher volatges as insulation will be a problem inside the alternator ( moving machine) for higher volatge. The best stretigy is to generate at 11kv and futher step up using transformer ( static machine) to much higher voltages.

Cheers!!

Answer 4

Please rearrange these words into a question.