CU HVDC System

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Great River Energy’s CU HVDC Project, a bipolar 1,000-megawatt HVDC bulk power transmission system between Underwood, North Dakota and Dickinson (near Minneapolis), Minnesota, was built and commissioned by ABB in 1978.

It transmits power from the Coal Creek generating plant in North Dakota to the Minneapolis area in Minnesota. The HVDC system was chosen for the CU Project for its stability over long distance and low environmental impact. Coal Creek converter station

Valve hall with air-cooled valves

The converter stations are of the same generation as Skagerrak and Inga-Shaba, i.e. with air-cooled thyristor valves.

CU was one of the first project to employ metallic return during monopolar operation and the first to have an ABB DC-breaker as metallic return transfer switch.

The project's name "CU" originates from the name of the first owners: Cooperative Power Authority (CPA) and Uniited Power Authority (UPA). 

In 2002 ABB received an order for a control system upgrade to the fully digital MACH 2™ system. The old analogue system from the mid 1970's was replaced in 2004.

Main data
Commissioning year:	1978
Power rating:	1 000 MW
No. of poles:	2
AC voltage:	235kV (Coal Creek), 350 kV (Dickinson)
DC voltage:	±400 kV
Length of overhead DC line:	687 km
Main reason for choosing HVDC:	Long distance, network stability