Power Lines

[tom_pay]

Hi

I don't know whether this is a silly question or not, but Ill ask it anyway!


Why are the overhead power lines and our mains power AC?


I was told when I was in high school that it was more efficient. To do so.

Is it because the average current/voltage is 0?

Or is more complex involving inductance and resistance?


Tom

 

[Reloadron]

I was told when I was in high school that it was more efficient. To do so.

That would be correct. The early power grids in the US were actually DC and later changed to AC. The use of AC allows the use of transformers and less line loss. It was the thinking of Nikola Tesla who paved the way for today's power distribution grids globally. That is it in a nutshell. DC is just plain impractical for mains power distribution.

Ron

 

[tom_pay]

Ohhhhhhhhhhhh,

That makes sense. That Telsa man is very clever!!!

Thanks

Tom

 

[BrownOut]

Just to elaborate, when power is sent over miles and miles of wire, it is sent as a very hight voltage. Now being a high voltage, the current can be smaller for the same power per the equation P(delivered)=E*I. Now, the line loss would be proportional to the current per P(loss)=I*R, where R is the resistance of the overhead wire. By sending power at very high voltage, the current (I in the equations) can be made very small, and thus the power loss in the last equation can be very small. Because the power is delivered as AC, the voltage can be stepped down just before it enters the building.