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Specifications

Our scope of supply typically includes equipment, engineering and site supervision.

Our scope of supply typically includes equipment, engineering and site supervision. Each system is engineered to the specific requirements of the plant.

Control hardware includes a PLC-based digital control cabinet with touchscreen local operator interface, pilot valve electro-hydraulic interface manifold(s), and electronic speed and servomotor position sensors. The existing low pressure oil system is usually retained.

Installation can be done by your crew, or we can provide complete turn-key services. During the outage, an experienced Field Service Engineer will be on hand to assist with installation and provide final commissioning and testing services.

PLC Governor System

The heart of each new governor system will be an Allen-Bradley Programmable Logic Controller (PLC).

The PLC will be mounted in a NEMA 12 cabinet that includes:

Governor PLC
    » PLC Rack
    » CPU Module
    » Power Supply Module (125VDC)
    » Discrete Input Module(s)
    » Discrete Output Module(s)
    » Analog Input Module(s)
    » Analog Output Module(s)

 Cabinet Power Supply (125VDC/24VDC)
 Terminal Blocks (as needed)
 Interposing Relays (as needed)
 Analog Isolators (as needed)


Typical Control Cabinet with color touchscreen on door

Local Control Switches and Meters

The following devices can be mounted on the door of each cabinet to provide a backup Local Operator Interface. This list can be customized to suit your preferences.

     Gate Position Meter
     Governor Setpoint Meter
     Tachometer
     Other Indication
     Emergency Stop Pushbutton
     Local / Remote Control Switch
     Unit Auto Start/Stop Pushbuttons
     Raise / Lower Governor Setpoint


Typical Control Cabinet Interior
Local Operator Interface: Color Touchscreen

A 6 color touchscreen is proposed to serve as the Local Operator Interface. The touchscreen will be mounted on the control cabinet door and will communicate with the PLC governor system. An Emergency Stop pushbutton will also be provided.


Typical Touchscreen Display
Provides local control and monitoring of all governor
functions, gains and tunable parameters

The touchscreen computer operates independently and automatically establishes communication with the PLC upon boot-up; no operator intervention is required. System screens are stored in non-volatile memory.

The basic screens described below will be provided by AGC. Touchscreen software can be provided to allow site staff to modify or add new screens.

The system will have the following capabilities:

     Local Control of the Unit
     Local Display of Unit Information
     System Alarm Display
     Input / Output (I/O) Status display
     Event Log
     Basic Trending of Unit Sata
     Access to Tunable Parameters for the Unit
     Serial Port for Printing

Primary Speed Sensing PT Interface

Primary speed sensing will be done via an American Governor Speed Signal Module connected to a generator Potential Transformer (PT). 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

Redundant speed sensing offers enhanced reliability by backing up the primary PT speed signal with an independent speed signal from a new Zero Velocity Pick-Up (ZVPU) mounted on the generator. This high-resolution pick-up detects the rotation speed of a toothed wheel (provided by others) that is mounted on the generator shaft.

The ZVPU can reliably detect rotational speed down to 0.0 rpm and is thus ideally suited for brake actuation and creep detection, if required. The governor can use either signal under normal operation, and software will be provided in the Governor PLC to detect failure of either the Primary or Back-up speed signal, which will generate an alarm.

Loss of both signals will result in Emergency Shutdown of the unit.

Cabinet Power Supply

A 125VDC/24VDC cabinet power supply will be provided to power the proportional valve, accessory equipment and field devices.

Electro-Hydraulic Interface (EHI) Assembly

The EHI assembly is the basic connection between the PLC Governor and the existing distributing valve. The EHI controls the flow of oil to the distributing 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.

Hydraulic Manifold
A custom manifold for the mounting of valves. Includes shutdown shuttle assembly for independent shutdown via solenoid valve (blocks control flow from proportional valve).

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