Minnesota Power HVDC Modernization Project

To modernize the Minnesota terminal of the existing Square Butte high voltage direct current (HVDC) line and implement the latest technology, new buildings and electrical infrastructure are proposed on a new site near the existing Arrowhead Substation in St. Louis County, MN. The new HVDC terminal is proposed to connect to the existing alternating current system by constructing a new St. Louis County 345 kilovolt (kV)/230 kV substation near the current Arrowhead Substation. The new HVDC terminal would be connected to the St. Louis County Substation by less than one mile of 345 kV high voltage transmission line (HVTL). The new St. Louis County Substation would be connected to the existing Arrowhead Substation by two parallel 230 kV HVTLs less than one mile in length. Additionally, a short portion of the existing ±250 kV HVDC line  will need to be reconfigured to terminate at the new HVDC terminal.

Updates and expansions are required at the other end of the Square Butte line in North Dakota as well, to be regulated by the North Dakota Public Service Commission. The project includes cupgrading to bi-directional transmission while maintaining the same voltage and power transfer capability along the Square Butte HVDC line.