Pete HahnloserThe Minnesota Public Utilities Commission has approved a certificate of need and route permit for Minnesota Power’s high-voltage direct-current (HVDC) modernization project. The existing 465-mile HVDC Square Butte transmission system was commissioned in 1977 to deliver wind energy from North Dakota.
The project is the result of increasing outages and control system failures that highlight the need for upgrades to both transmission lines and terminals.
The Minnesota portion of the work will replace facilities at the Arrowhead Substation in Hermantown, where the HVDC power is converted to grid-compatible alternating current. It will also involve constructing three transmission lines, each less than a mile long, to link the new converter station to a new substation and Minnesota Power’s transmission system. The project as approved provides the option to increase capacity from the current 550 megawatts to 900 MW.
The commission’s decision follows findings by an administrative law judge that HVDC line outages result in costs from congestion, reserving transmission on another party’s system, replacement energy and lost production tax credits. With current failure rates, the estimated annual costs due to outages are at least $7 million – and likely significantly higher.
Square Butte is one of the few HVDC lines in the U.S. They transmit power over long distances with less energy loss than traditional high-voltage lines. Minnesota Power estimates project costs to be between $600 million and $940 million and has secured state and federal funding to help cover some of these costs. Construction could start as early as this year, with the project expected to be operational between 2028 and 2030.
“This existing transmission system is 47 years old and needs to be replaced. We also need to add new technology to ensure we have the necessary capacity now and into the future,” Commissioner Hwikwon Ham said.
Photo by Wtshymanski
