Also known as Path 65, the Pacific DC Intertie is an HVDC power transmission line running 846 miles from Celilo, OR to Sylmar, CA. It supplies 3,100 MW of hydroelectric generated power to the hordes of people in the Los Angeles area. This is over 48% of LADWP's peak capacity. More information is available at this Swiss contractor site.
This line is visible for many miles from highways 14 and 395. Many of its pylons are unique in that they use one verticle structure that tapers to a point on a concrete pad, and they have only 2 arms to support the power lines. In my photo, you can see the HVDC line running along side a traditional AC line. The lines carry 500 kV DC each. According to Wikipedia, we can thank President John F. Kennedy for approving this public works project in 1961. It was completed in 1970 and has been upgraded several times since.
I took these pics while trying out my new Land Rover's "sand mode" at the Jawbone Canyon OHV area north of Mojave, CA. You can see from the photos that the AC lines generated much stronger magnetic and electric fields. The electric field meter was pegged under the AC lines. The magnetic fields measured 25 and 7 milligauss for the AC and DC lines, respectively.
The first two photos are under the HVDC line. The first shows the electric field and the second shows the magnetic field. The next two photos are taken under the AC lines and they show the electric and magnetic field strengths there.
Scientific American recently proposed that building new HVDC transmission corridors can efficiently bring solar power from the American southwest to the people in other states. This was part of their Jan 2008 cover story: A Solar Grand Plan.