CU / Square Butte Crossing

Crossing of 400 kV DC line CU ( on large pylons) of 250 kV DC line Square Butte ( on small pylons). http://en.wikipedia.org/wiki/File:HVDC_Cro... (Wikipedia CC)

Upon first glance, one would probably not recognize that this site is a unique one. But enthusiasts of electrical oddities and inventions know the CU/Square Butte Crossing just southeast of Wing, North Dakota, is the only place outside of China and India where two overhead DC power lines cross.

As you can easily see on the pylons, both of these power lines carry only two conductors. Normally, power lines hold three or a multiple of three conductors as it’s required of three phase-AC. The only other power lines with two conductors are found in areas where single phase-AC is used to provide electricity for railways.

These lines are special as they power transmission systems used for interconnecting asynchronous power grids and very long overhead cable lines. Prohibitively expensive, this type of technology is only used when there is no other method possible for the supply of power in a region.