PHT Project

1 MW, NC

Year: 2021
Running Gear: 2 Vertical shaft Francis turbines with synchronous generators
Scope: Replacement of control system, exciters, and HPUs

Originally part of a large cotton mill complex in North Carolina dating back to the 1800s, this 1 MW hydropower plant stayed in operation into the 2000s, longer than the rest of the declining mill town. The cotton mill itself finally shut down in 1996, costing hundreds of jobs. PHT was hired as part of a larger revitalization effort; the mill complex in 2021 had seen significant restoration, including restaurants, breweries, short term lodging and a large campus of apartments and single-family homes. The current owners of the larger mill complex made a significant investment to restore two of the three existing hydropower generating units.

The project in 2021 consists of a masonry dam and intake structure, forebay, and powerhouse with two restored vertical shaft Francis turbines and synchronous generators. The powerhouse is now split into two smaller rooms within the expansive restored mill building, which has been converted into a mixed-use space including a restaurant, offices, and apartments.

PHT was hired to provide the control system, excitation, and new hydraulic power units for wicket gate control, while another party was hired to complete the required millwork and running gear restoration. The plant was re-commissioned for operation in summer of 2021.

PHT provided a new control and automation system for the plant, including new Power-Tronics exciters, and additional instrumentation and machine condition monitoring. Like most retrofits of older equipment, PHT installed new water level sensors, RTD temperature sensors on the stator, bearings and oil loops, added RPM and vibration sensors, oils level sensors, and more.

As is typical, PHT designed and assembled the hardware and control cabinets for this project at our shop in NC, and then traveled to the power plant site for installation and commissioning. The new PHT controls include numerous standard features including automatic pond level control, automatic starting, and unit dispatch, machine condition monitoring, push notifications, an easy-to-use touch screen user interface, and secure remote access that allows monitoring and operation from off-site. Periodic, automated reports allow both O&M and management staff to track plant operation, and to improve plant operations and uptime.

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