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Dry Fork Station journey to startup begins

Gillette, Wyo. - One of the first major start-up processes has been completed.

Basin Electric Power Cooperative - March 5, 2010

Gillette, Wyo. - One of the first major start-up processes has been completed. There's many more remaining. On the outside, the Dry Fork Station under construction near Gillette, Wyo., looks like it’s ready to roll. But on the inside, much work remains to be completed before the new power plant can start generating electricity.

Even though commercial operation is scheduled for mid-2011, the process of getting plant systems up and running, called commissioning, has already begun.

The first step completed on Feb. 25, was back-feeding electricity to the plant's reserve auxiliary transformer through the switchyard from the transmission lines that will ultimately carry electricity from the plant. The reserve auxiliary transformer feeds electricity to the high-voltage switchgear within the power plant. Up until that point, the temporary power supply for the construction site came from a substation owned by Basin Electric member Powder River Energy Corporation.

Doug Ramsey, Basin Electric construction manager at the Dry Fork Station, says the backfeed process involved 35 of more than 640 steps on the checklist leading to commercial operation.

"Crews from Sargent and Lundy and Basin Electric proceeded with the back-feed process cautiously to make sure all protective relays along the way would trip if problems were encountered," Ramsey says. Detailed lock-out/tag-out procedures were followed to ensure safety for all personnel on site.

Electricity was successfully fed through the reserve auxiliary transformer at 8:33 a.m. Feb. 25. From there, the main breakers were closed on the 13.8-kilovolt switchgear, feeding electricity into the power plant. About 24 hours later, Ramsey says the reserve transformer was de-energized, and samples of its oil were taken for testing before re-energizing it.

During normal plant operations, Ramsey says the reserve auxiliary transformer is disconnected and the plant auxiliary transformer - located near the generator step-up transformer - provides power to the high-voltage switchgear. The reserve transformer is used as back-up to the plant auxiliary transformer.

Clyde Bush, Basin Electric vice president of coal-based resource development, says the high-voltage switchgear feeds the largest plant motors. Voltage is also reduced to more usable voltages throughout the plant to run the balance of lower horsepower plant equipment - all necessary to move into more complex steps in plant startup, like the production of demineralized water in April.

"After we have the power and the water available within the plant, we can then move to filling the boiler and the application of 150 percent of designed pressure - called a hydrostatic test - to prove the mechanical integrity of the boiler. This is an extremely high-pressure test in excess of 4,000 pounds per square inch to validate the integrity," Bush says. This is scheduled for May.

Once they are confident in the physical integrity of the boiler, Bush says they can move on to the first fire of fuel in the boiler. In the case of the Dry Fork Station, the first fuel will be propane. This creates steam, which is necessary for the next step, called steam blows. Steam pressure is built in the boiler, and then released to the atmosphere through a rapid opening valve process. Bush says this helps clear debris from the boiler.

Once the boiler has been cleaned, both mechanically and chemically, it's time to introduce coal to the boiler for the first time. "We are then able to roll the turbine-generator for the first time," Bush says. The generator is then synced with the transmission system.

Once all plant systems have been brought into operation, they will be performance tested to ensure every piece of equipment meets the terms of the contracts.

Construction of the Dry Fork Station remains on schedule. As of late February, construction was about 74 percent complete. It's scheduled for commercial operation in May 2011.

About Basin Electric Power Cooperative

Basin Electric is a consumer-owned, regional cooperative headquartered in Bismarck, N.D. It generates and transmits electricity to 135 member rural electric systems in nine states: Colorado, Iowa, Minnesota, Montana, Nebraska, New Mexico, North Dakota, South Dakota, and Wyoming. These member systems distribute electricity to about 2.8 million consumers.

Basin Electric’s generating resources include: two coal-based power plants in North Dakota - the Antelope Valley Station, Beulah, and the Leland Olds Station, Stanton; a coal-based power plant in Wyoming - the Laramie River Station, Wheatland; three peaking stations – the Spirit Mound Station, Vermillion, S.D.; the Groton Generation Station Groton, S.D., and the Wisdom Unit 2 Station, Spencer, Iowa; nine combustion-turbine generators (natural gas) in the Gillette, Wyo., area; four wind turbines - two near Minot, N.D., and two near Chamberlain, S.D.; and 80 wind turbines near Minot, N.D. (2010). Basin Electric is also the sole purchaser of electricity from sources operated by others including: six baseload waste-heat stations owned and operated by Ormat Technologies Inc. along the Northern Border Pipeline; the output of three wind farms owned and operated by NextEra Energy Resources, Juno Beach, Fla. (These wind farms are located near Wilton and Edgeley/Kulm, N.D.; the other is near Highmore, S.D.) Basin Electric has long-term, purchase power agreements of varying capacities from the George Neal Station Unit 4 (coal-based), Sioux City, Iowa, operated by MidAmerican Energy; the Walter Scott, Jr. Energy Center (coal-based) units 3 and 4, Council Bluffs, Iowa, operated by MidAmerican Energy; the Wisdom Station (coal based), Spencer, Iowa, operated by Corn Belt Power Cooperative; peaking stations located in Spencer, Estherville, Pocahontas, and Webster City, Iowa; the Duane Arnold Energy Center (nuclear), Cedar Rapids, Iowa, operated by NextEra Energy Resources; the Municipal Energy Agency of Nebraska; and three Iowa wind farms – near Superior/Lakota, operated by Iowa Lakes Electric Cooperative; in Hancock County operated by NextEra Energy Resources and in Palo Alto County operated by Crosswind Energy, LLC. For more information, go to www.basinelectric.com.