Siemens to supply two VFDs to South Dakota power plant |

Siemens to supply two VFDs to South Dakota power plant

December 5, 2012 - Siemens 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, 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. 
Siemens Industry Sector is the world’s leading supplier of innovative and environmentally friendly products, solutions and services for industrial customers. With end-to-end automation technology and industrial software, solid vertical-market expertise, and technology-based services, the sector enhances its customers’ productivity, efficiency and flexibility. With a global workforce of more than 100,000 employees, the Industry Sector comprises the Industry Automation, Drive Technologies and Customer Services Divisions as well as the Metals Technologies Business Unit.
The Siemens Drive Technologies Division is the world’s leading supplier of products, systems, applications, solutions and services for the entire drive train, with electrical and mechanical components. Drive Technologies serves all vertical markets in the production and process industries as well as the infrastructure/energy segment. With its products and solutions, the division enables its customers to achieve productivity, energy efficiency and reliability. 
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