Corp. (WPS), located in Rothschild, Wis., is a public utility serving more than 440,000 electricity customers in 11,000 square miles of northeastern Wisconsin and an adjacent portion of Michigan’s Upper Peninsula. The company operates a network of coal-fired, nuclear, hydroelectric, wind and natural gas peaking power plants that provide up to 2,000 MW of electric power. Its innovative approach to automating power generation processes sets it apart from many other utilities.

About two-thirds of the WPS generation capacity is provided by coal-fired plants, and the company has enhanced the efficiency of those plants—while significantly reducing the cost of producing power—by developing its own open-architecture equivalent to the standard distributed control systems (DCSs) that run other utilities’ coal-fired plants.

Plant management of the company’s three coal-fired units at the Weston complex has deployed personal computers (PCs), programmable logic controllers (PLCs) and software packages to create their own DCS system at far less cost for both initial system implementation, and life cycle cost of ownership and maintenance. The control systems have enabled the integrated control of three plants that were built over several decades. They also have given plant management and operators the ability to fine-tune operations more efficiently, because multiple systems now share a common historian database for all three coal-fired plants, as well as two peaking units.

In the mid-1990s, the original control systems were creaking with age, and WPS management realized they needed to be replaced, not just to facilitate plant operation, but also to make the units run more efficiently. If the company could produce power from the same equipment at less cost, then the building of additional generating units could be stretched out over time.

WPS decided to replace the original pneumatic control systems with PLCs to control equipment functions, and to use PCs running human-machine interface (HMI) software to enhance operator interaction with the units. A network of Modicon PLCs supplied by Paris-based Schneider Electric was installed for equipment control, while PCs running InTouch HMI software from Wonderware, a Lake Forest, Calif.-based unit of Invensys Process Management, were deployed as operator interfaces to the PLC controls. To emulate the functionality of a typical DCS system, WPS installed the ControlPlus distributed control software developed by Standard Automation, a Texas-based Wonderware authorized distributor. The complete set of software products was provided through GS Systems, Wonderware’s distributor based in New Berlin, Wis.

On the money

“This solution was exactly what we needed because it gave us all the functionality of a standard DCS system, but it was much less expensive to implement and it allowed us to integrate under one control system all the equipment that we had installed from various manufacturers over a 40-year period,” says Daniel Snyder, WPS instrument and control team leader. “We didn’t have to worry about whether our steam generators came from Babcock & Wilcox or Combustion Engineering, or whether our turbine generators came from Allis Chalmers or GE. All of our coal-fired processes are 100 percent under automatic control.”

Snyder observes that production requirements have become so complex over the last decade that there is “no way” that human operators could coordinate all of the critical steps involved. Instead, “the historian maintains complete records on every step in the process,” he says, “so we have an audit trail on everything that’s done by the control system. The trending software allows both operators and management to quickly and easily view and analyze any parts of the process, and we often can find potential problems before they even occur.”

Has the approach led to bottom-line improvements? You bet, Snyder responds. “This has made us far more efficient,” he says. “In effect, we can fine tune the process as it’s running.”

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