PHT Project

225kW, NC

Year: 2008
Running Gear: One Francis turbine and vertical shaft synchronous generator.
Scope: Controls, switchgear, and wicket operator.

This small hydroelectric plant is located at an historic site that was originally built to supply shaft power, and later electricity, to a textile mill.  When it became feasible, the plant was operated in parallel with grid power, and eventually the textile mill was shut down.  Although still in mostly running condition when it was purchased by its current owner, the plant retained much of its original equipment, which required an on-site operator. The original Westinghouse control board did not have the necessary protection and automation to operate on-grid and unattended, so PHT was hired to provide a modern control system.  

The upgrades from PHT included a new PLC and utility grade, Basler multi-function protective relay to control and protect the generator.  The rotary exciter was replaced with a Payne exciter controlled by the PLC.  Old mechanical switchgear was replaced with a vacuum contactor.  The original Woodward governor was disconnected (though left intact) and replaced with a hydraulic power unit and cylinder, controlled by the PLC. The owner is now able to operate the plant largely unattended, with PHT’s algorithm for automatic headpond level control throttling the turbine as necessary to follow the changing river flow.


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