Siemens, in partnership with Fougner Engineered Sales, a supplier of electric equipment and supplies, has been selected by Otter Tail Power Company to provide two Robicon Perfect Harmony variable frequency drives (VFD) for environmental upgrades at the Big Stone Plant, a coal-fired power plant that the company operates in Big Stone City, S.D.
In May, plant owners Otter Tail Power Company, Montana-Dakota Utilities Co., and NorthWestern Energy, approved a plan calling for $490 million in environmental retrofits, including a new air-quality control system to be commissioned within five years of the Environmental Protection Agency’s approval of the South Dakota Regional Haze State Implementation Plan.
Two Siemens Robicon Perfect Harmony WCIII drives will support a new dry scrubber to reduce sulfur dioxide. Plans also call for a selective catalytic reduction (SCR) unit to reduce emissions of nitrogen oxide. According to an Otter Tail Power Company spokesperson, these retrofits are expected to reduce both nitrogen oxide and sulfur dioxide by 80 to 90 percent.
“Variable frequency drives offer a number of benefits, including cost savings. Since it’s not necessary to operate fans and motors within a power plant at 100 percent power, these drives increase efficiency,” says Mark Fougner, President of Fougner Engineered Sales. “Siemens Robicon Perfect Harmony Drives have a technological advantage with their cell bypass feature, and the Siemens team has proven to be a trusted partner throughout this project.”
Siemens Robicon Perfect Harmony Drives are unique, as each uses a series of low-voltage cells linked together and scaled precisely for a wide range of voltage and output power. The cell bypass ensures automatic bypass of a failed power cell in less than 500 milliseconds and instead of shutting down the entire drive, a process-tolerant protection system (ProToPS) provides a hierarchical system of warnings. This control strategy allows time to evaluate the situation and respond appropriately. This concept also enables easy access to drive components for scheduled maintenance. Siemens VFDs also meet IEEE 519 standards for input power harmonic distortion.
Siemens Robicon Perfect Harmony Drives are well suited to the chemical, petrochemical, oil and gas, and power generation industries because they can ride through voltage dips, have a small footprint, and require no output transformer, harmonic line filters, or power factor compensation.
Otter Tail Power Company estimates that retrofits to the 475-MW Big Stone Plant, in operation since 1975, will be completed by mid-2015. Big Stone Plant is one of three coal-burning power plants that produce about 70 percent of the company’s electricity. The company also owns six hydroelectric stations, owns and purchases wind-generated electricity, and operates three combustion-turbine backup plants. The company also buys and sells bulk power on the wholesale market.
Otter Tail Power Company, a subsidiary of Otter Tail Corporation (NASDAQ Global Select Market: OTTR), is headquartered in Fergus Falls, Minn. It provides electricity and energy services to more than a quarter million people in Minnesota, North Dakota and South Dakota. To learn more about Otter Tail Power Company, visit www.otpco.com. To learn more about Otter Tail Corporation, visit www.ottertail.com.
For more information about Siemens Robicon Perfect Harmony variable frequency drives, visit http://www.industry.usa.siemens.com/drives/us/en/electric-drives/medium-voltage-drives/Pages/medium-voltage-drives.aspx?stc=usidt100007&sp_source=usidt100007.
