Critical transmission upgrade finishes strong

The high-voltage, direct-current (HVDC) upgrade that has been years in the making was completed May 17 and put into commercial use. This project has been one of Great River Energy’s most significant capital investments over the last several years and was needed to help ensure the continued reliability of one of the cooperative’s most critical assets.

Great River Energy’s HVDC system works like an extension cord that delivers power directly from the 1,140-megawatt Coal Creek Station power plant in central North Dakota to Minnesota. The system consists primarily of a 436-mile transmission line and two converter stations. A converter station at Coal Creek Station in North Dakota converts electricity to direct-current power so it can be transmitted over the HVDC power line to another converter station, just outside of Buffalo, Minn. There it is converted back to alternating-current power so it can be sent out through the electric system to Great River Energy’s member-owner cooperatives.

Nearly all the equipment housed in the converter stations was removed and replaced with advanced technologies.

The project went according to plan with demolition, construction and commissioning. Final testing was completed May 15-20. Crews finished two days ahead of schedule and the project is expected to finish under budget.

The high-voltage, direct-current upgrade finished on time and under budget. The four valve halls at the two converter station sites (one near Buffalo, Minn., and the other near Underwood, N.D.) were updated with new conversion technology, which will ensure the continued reliability of one of Great River Energy’s most critical assets.

“The success of the HVDC project demonstrates the capabilities, dedication and teamwork of our transmission employees,” said Tony Ramunno, director of power delivery at Great River Energy. “The completion of this project demonstrates the value of a well-thought-out plan, excellent project management, a capable and dedicated team and our ability to successfully collaborate, negotiate and work with ABB – a mega, multi-national vendor.”

Vice President and Chief Transmission Officer Priti Patel said the upgrade offers additional flexibility for Great River Energy and its member-owners.

“We look forward to the system serving us reliably for decades, regardless of how our generation mix evolves or what the source of generation is at the end of the line,” Patel said. “I am so proud of our transmission team and their focus on safety and excellence throughout this project.”

Prior to being placed in operation, engineers used drones to purposely create a short-circuit in various parts of the line to cause the system to simulate a fault, such as a lightning strike. Engineers did this to see how the new HVDC converter station equipment would respond after the upgrade. All tests showed the system responded as it should.

The advanced technology reduces the number of power conversion electronic components by approximately 70 percent. In addition, fire hazards were reduced with this upgrade as oil-based capacitors were removed and air-cooled valves were replaced with water-cooled models. Great River Energy expects to see efficiency gains of at least 7 megawatts as the upgraded equipment conserves more electricity and the upgrade increased in operating voltage.