Expert controls replace legacies, 3% boost
Progress Energy Inc.’s Roxboro Unit-2’s ramp-rates improved from 91% in 2004 to 94% through November 2005, as well as improving the unit’s superheat temperature by +/-5 oF regulation during load ramps.
Tighter system integration and new controls at the 10th largest U.S. power plant improved load ramp rates by 3% and better regulated temperature. Emerson Process Management said that its Power & Water Solutions group is replacing legacy controls in all four units of Progress Energy Inc.’s (PE) 2,462 MW steam-plant in Roxboro, NC, with Emerson's Ovation expert-control system. The multi-year project began in early 2005, with installa-tion of Unit 2 controls, continuing as controls are installed in the plant’s remaining three units. It’s part of PE’s move to a centralized, integrated control strategy for Roxboro.
Although in place only a few months, coordinated controls reportedly have helped Unit-2’s load ramp-rates improve from 91% in 2004 to 94% through November 2005. Additionally, tighter control strategies have helped to improve Unit 2’s superheat tem-perature regulation by +/-5 oF during load ramps.
Old unit-control systems were at maximum capacity, precluding addition of new con-trols for selective-catalytic-reduction (SCR) and scrubber systems. Now Unit 2 has started-up a recently added SCR-system along with the plant controls. Moreover, a flue-gas desulphurization system, using FOUNDATION fieldbus, will also link to the new con-trols.
The new, integrated control system replaces distributed control systems (DCS) that were data-linked to numerous PLC-based plant systems. DCS systems and PLCs all used Genius I/O blocks encompassing over 20,000 remote I/O-points. Due to a tight outage schedule and added costs, it was not feasible to replace existing Genius I/O with new modules.
Migrating controls for the four-unit plant posed a number of challenges, including:
— Richard Phelps, senior editor, Control Engineering