Our scope of supply typically includes equipment, engineering and site supervision. Each kit includes a PLC-based digital control cabinet with touchscreen local operator interface, pilot valve electro-hydraulic interface manifold, and electronic speed and gate position sensors.
The PLC cabinet can be physically mounted and wired by your staff or others using the drawings we provide. During the outage, an experienced Field Service Engineer will be on hand to assist with installation and provide final commissioning and testing services. Click any component below for more details.
PLC Governor System
The heart of each new governor system will be an Allen-Bradley™ Programmable Logic Controller (PLC).
The new controller and accessories will reside in a wall-mount control enclosure that includes the following devices:
Local Operator Interface: Color Touchscreen
Mounted on the front door of the PLC Governor, a 6” color touchscreen Human Machine Interface (HMI) will serve as the primary Local Operator Interface. Local control screens described below will be provided by AGC and will allow operators full access to all system control modes.
The touchscreen operates independently and automatically establishes communication with the PLC Governor upon boot-up; no operator intervention is required and system screens are stored in non-volatile memory. HMI programming software and cable are included to allow you to modify or add new screens.
In addition, a door-mounted Emergency Shutdown push button will be provided.
Cabinet Power Supply
A 125VDC/24VDC cabinet power supply will be provided to power the Governor PLC, proportional valve, accessory equipment and field devices.
Electro-Hydraulic Interface (EHI) Assembly for Gateshaft Governors
The EHI assembly is the basic connection between the PLC Governor and the existing relay valve. The EHI controls the flow of oil to the relay valve, which regulates the flow of oil to the servomotor to open or close the wicket gates.
The assembly includes the following devices:
Proportional Control Valve
Enables servomotor control via PLC during normal operation. This high-response valve provides closed-loop control of distributing valve spool position.
Solenoid Shutdown Valve
Enables emergency shutdown independent of the PLC. When de-energized, the solenoid valve causes the distributing valve spool to move fully in the close direction, causing the servomotor to close at the fastest rate allowed by the stop nuts.
A custom manifold for the mounting of valves. Includes shutdown shuttle assembly for independent shutdown via solenoid valve (blocks control flow from proportional valve).
Primary Speed Signal
Primary speed sensing is done via an American Governor Speed Signal Module connected to a generator Potential Transformer. Our high-resolution Speed Signal Module provides one 0-200% analog output for metering and one high-resolution analog output for synchronizing and on-line droop control.
The module is compliant with IEEE 125 “IEEE Recommended Practice for Preparation of Equipment Specifications for Speed-Governing of Hydraulic Turbines Intended to Drive Electric Generators.” Back-up speed sensing is available as an option.
Relay Valve Position Feedback (LVDT)
The EHI requires an accurate and stable relay valve position signal in order to function closed-loop. A Linear Variable Differential Transformer (LVDT) will be provided for relay valve feedback.
Mounting hardware, signal conditioner and connector will be included.
Servomotor Position Feedback (MLDT)
The Magnetostrictive Linear Displacement Transducer (MLDT) is a superior non-contact alternative to traditional low-cost linear position feedback devices such as linear potentiometers or string pots. An MLDT will be provided for electronic feedback of Wicket Gate servomotor position.
Mounting hardware and connector will be included.
Assemble, Wire & Test
American Governor will assemble and wire the complete PLC governor system in Ivyland, PA. Your system will be connected to our Turbine Simulator, which will be programmed to mimic site conditions.
All hardware and software will be tested completely before leaving our factory.
PLC Control Software
American Governor will provide governor control software adapted from proven software algorithms. Typical functionality includes: