Major construction to commence on premiere transmission system

One of the most critical, best-performing features of Great River Energy’s electric system will become even more reliable this summer after the cooperative upgrades its unique high-voltage, direct-current (HVDC) transmission system with today’s technology.

Great River Energy’s HVDC system works like a 436-mile extension cord that delivers power directly from the cooperative’s largest power plant in North Dakota, Coal Creek Station, to Minnesota.

“This has been one of the most reliable HVDC systems in the world, and it has served us and our member-owner cooperatives very reliably for 40 years,” said Priti Patel, Great River Energy’s vice president and chief transmission officer. “It’s a highly valuable asset that needs to be upgraded with current technology to ensure our high standards of reliability into the future.”

Crews locate cabling during a May 2018 converter station outage to prepare for the refurbishment this spring.It is difficult to foresee a future where the HVDC system does not have significant value for Great River Energy and the market, regardless of what the source of generation at the end of the line could be in the future, Patel said.

The system consists primarily of a 436-mile transmission line and two “converter stations.” A converter station at the power plant 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.

Those converter stations are where all the upgrades will take place. Nearly all the equipment that is housed inside them will be removed and replaced with advanced technologies.

HVDC systems are unique because they deliver electricity in direct current rather than alternating current, which is the standard for most electric systems.

“There are only a few systems like these in the United States,” said Greg Schutte, Great River Energy’s project manager for the HVDC upgrade.

The main benefit of HVDC systems is the ability to deliver electricity more efficiently over long distances than alternating current systems.

“There is always some power lost in delivery when you transmit electricity over a power line,” Schutte said. “But over long distances, those losses are significantly lower on direct-current systems than alternating current systems.”

Great River Energy has been preparing for this major upgrade since 2011. It will be completed over a 74-day period starting next month.