PHT Project

500 kW, CT

Year: 2014
Running Gear: Five 100kW prototype horizontal shaft Kaplan turbines with induction generators.
Scope: Control system for a new power plant at an existing dam.

This project is located in Connecticut at an existing stone dam, immediately downstream of a larger USACE Dam.  An entirely new intake, penstock, and powerhouse were built for this new hydroelectric plant.

PHT was selected to provide the control system for the prototype turbine generating units.  This included our usual PLC and touch screen, 5 generator protection relays, and vacuum contactors.  The five generators are induction type; therefore PHT also designed and supplied a switched capacitor bank to control the plant power factor.  The capacitor bank uses 3 capacitors (20, 40 and 80 kVAr) to provide reactive power in 20 kVAr steps from 0 to 140 kVAr.  The turbine wicket gates and blades are controlled by induction gearmotors via variable frequency drives, and position feedback is by quadrature encoders, both supplied by the customer.  Fortunately, the Productivity3000 PLC we use is powerful and flexible enough to be easily adapted to this equipment.

These are prototype turbines, so additional instrumentation was included compared to a more typical installation.  The plant has level sensors in both the forebay and tailrace, so that net head is known.  An ultrasonic flowmeter in the penstock provides total plant flow.  Since flow, head, and power output are all known, the total plant efficiency can be automatically calculated and displayed.  The Kaplan blade cam curves are user-adjustable, allowing easy adjustment to improve efficiency.

This is the first of two projects completed by PHT for this customer.


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