Stability over long distances and low environmental impact
Great River Energy’s CU HVDC Project, a 1,000 MW ± 400 kV bulk power transmission system between Underwood, North Dakota and Dickinson, Minnesota, was built and commissioned by Hitachi Energy in 1978. The project's name "CU" originates from the name of the first owners: Cooperative Power Authority (CPA) and United Power Authority (UPA).
The link transmits power from the Coal Creek generating plant in North Dakota to the Minneapolis area in Minnesota, a distance of 700 km, because planners determined it was more efficient to generate and transmit electricity, rather than to transport fuel, over this long distance.
HVDC technology was chosen because of its stability over long distances and low environmental impact (availability of this HVDC system has been better than 99 percent). CU was one of the first projects to employ metallic return during monopolar operation, and the first to have a Hitachi Energy DC-breaker as metallic return transfer switch.
In 2002, Hitachi Energy won an order to upgrade the control system to the fully digital MACH system. Installation and commissioning was performed in 11 days for pole 1 and 9 days for pole 2, an outstanding record for a project of this complexity. During these periods the other pole remained in full operation and was not disturbed by the control equipment upgrade. Only a short, 1½ day, bipolar outage was needed.
Commissioning the HVDC control system in record time was made possible by thoroughly factory testing the MACH equipment, and by the dedication of the joint Great River Energy - Hitachi Energy team. The bipole was back in full operation on April 17, 2004.
In 2015, Hitachi Energy won an order from the electric cooperative Great River Energy to upgrade the converter valves, valve cooling systems, control and protection systems and other related equipment at the converter stations. In addition to modernizing the HVDC system, the upgrade helps to improve grid reliability and efficiency.
|Commissioning year:||1979; 2004; 2019|
|Power transmitted:||1,000 MW|
|Direct voltage:||±400 kV|
|Application:||Connecting remote generation; Upgrade|