Open Forum → Re: AC/DC power

DC has made a resurgence in recent years.

One of the limitations of AC is that the transmission lines act like radio transmission lines as they get longer. a quarter-wavelength of line at 60Hz is 775 miles in free space, probably about 500 in the real world. That's why the entire US cannot be tied into one grid. For long transmission lines, the load has to be matched to the voltage and the characteristic impedance of the transmission lines.

Los Angeles gets much of its electrical power as DC via two circuits called Path 27 and Path 65, also known as the Pacific Intertie.

Proposed 350 mile-long high-voltage DC line to be run from Montreal to NYC under Lake Champlain and the Hudson River:

»www.chpexpress.com

So I'm just curious. How do they convert 1000MW of DC power to AC for eventual use? That's got to be one big honkin' inverter.. And how do they do it with any sort of efficiency.

BTW the Chicago El runs on DC. The newer cars though all have inverters on them and use AC motors.

IF you Google HVDC, you'll find pages of links to info.

Efficiency is not hard when there are no restrictions on size and weight. Banks of thyristors driving an iron core transformer work quite well.
By the way a single 800kV DC line typically carries 8000MW, whereas three phase 760kVac carries only 3000MW.