Dynalectric Company, Washington, DC recently completed upgrade work on the Mirant Potomac River Generating Station. Special features of this project included control room consolidation, Separate Over Fire Air installation (SOFA), distributed control system upgrade for units 3, 4, and 5, a simultaneous parallel three track schedule and design-build.
Prior to the outages and control upgrades, workers constructed the central control room and associated systems. They installed new control consoles, monitors and uninterruptible power systems and installed three new Foxboro distributed control system (DCS) cabinets. Old equipment stations were removed and interference was cleared while allowing for uninterrupted operation of the facility. The work emphasized as much preparation for the outages as possible.
Units 3, 4, and 5 Outages
During each outage six Leeds & Northrop control cabinets were completely disconnected, removed and replaced with four Foxboro DCS cabinets. New wire was pulled between adjacent terminal cabinets and Foxboro cabinets and all terminations made. Cables were installed in the new cabinets and all terminations made. Interferences were cleared at higher elevations for boilermakers to install SOFA equipment. Lastly, conduit work was finalized and equipment connections were terminated. Many unforeseen challenges, such as deteriorated cable, were handled during the outages without extending the schedule.
A Lot of Work in 8 Months
Over 8 months,15,000 feet of rigid steel conduit was installed, more than 60,000 feet of cable was pulled and terminated, several hundred feet of cable tray was installed, and 27 terminal cabinets were built and installed. It is estimated that nearly 30,000 terminations were performed with half being done during the outages.