Square Butte is the designation of a

high-voltage direct current A high-voltage direct current (HVDC) electric power transmission system uses direct current (DC) for electric power transmission, in contrast with the more common alternating current (AC) transmission systems. Most HVDC links use voltages betwe ...

transmission line in the United States between the Milton R. Young Power Plant near

Center, North Dakota Center is a city in Oliver County, North Dakota, United States. It is the county seat of, and the only incorporated place in, Oliver County. The population was 588 at the 2020 census. History Center was founded in 1902. The city was named from ...

at and the Arrowhead converter station near Adolph (a neighborhood of the city of Hermantown near the city of

Duluth, Minnesota Duluth ( ) is a Port, port city in the U.S. state of Minnesota and the county seat of St. Louis County, Minnesota, St. Louis County. Located on Lake Superior in Minnesota's Arrowhead Region, the city is a hub for cargo shipping. The population ...

) at . It was built by

Minnkota Power Cooperative Minnkota Power Cooperative is an electrical generation and transmission cooperative based in Grand Forks, North Dakota. It wholesales electric power to rural electric cooperatives in North Dakota and Minnesota Minnesota ( ) is a U.S. s ...

and Minnesota Power and went in service in 1977. In 2009, an agreement was executed between the two companies whereby Minnkota gets the rights to all the power currently transmitted over the line (and which is now carried over a newly built 345kV transmission line) while Minnesota Power takes full ownership of the line to transmit power from new sources in the Center area. Square Butte can transfer up to 500

megawatts The watt (symbol: W) is the unit of power or radiant flux in the International System of Units (SI), equal to 1 joule per second or 1 kg⋅m2⋅s−3. It is used to quantify the rate of energy transfer. The watt is named in honor o ...

at a symmetrical voltage of 250 kV. The whole line is implemented as overhead line on steel lattice towers, with a single conductor per HVDC pole (i.e. a total of two for the HDVC bipole), with a length of 449 miles (749 kilometers). The line crosses the

Missouri River The Missouri River is a river in the Central United States, Central and Mountain states, Mountain West regions of the United States. The nation's longest, it rises in the eastern Centennial Mountains of the Bitterroot Range of the Rocky Moun ...

north of Price between and in a 718 metres long span. As is the case for modern HVDC-systems

thyristor A thyristor (, from a combination of Greek language ''θύρα'', meaning "door" or "valve", and ''transistor'' ) is a solid-state semiconductor device which can be thought of as being a highly robust and switchable diode, allowing the passage ...

static inverter An HVDC converter station (or simply converter station) is a specialised type of substation which forms the terminal equipment for a high-voltage direct current (HVDC) transmission line.Arrillaga, Jos; High Voltage Direct Current Transmission, s ...

s are used.

Crossing another HVDC line

Southeast of Wing, North Dakota, at Square Butte crosses CU, another HVDC powerline. This is the only crossing point of two HVDC overhead powerlines in the Western hemisphere.

Electrode line

The ground return

electrode line An electrode line is used in some high-voltage direct-current (HVDC) power transmission systems, to connect the converter stations to distant ground electrodes. Many long-distance HVDC systems use sea or ground return for the DC neutral current ...

starting at Adolph Static Inverter Plant is installed on portal pylons of the three phase AC-powerline from Adolph Static Inverter Plant to Marble Substation. It ends at {{Coord, 46, 55, 29, N, 92, 41, 50, W, type:landmark, name=End of electrode line of Square Butte. The electrode line starting at Adolph Static Inverter Plant consists of two underground 15 kV cables, each using aluminum conductors with a cross section of 380 mm².

External links

* ABB (2005)
Upgrade of control system for CU and Square Butte HVDC projects
Retrieved March 27, 2005.

THE SQUARE BUTTE HVDC SCHEME – Geographic map
Energy infrastructure completed in 1977 Electric power transmission systems in the United States Energy infrastructure in North Dakota Energy infrastructure in Minnesota Duluth, Minnesota 1977 establishments in Minnesota 1977 establishments in North Dakota Buildings and structures in Oliver County, North Dakota