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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.
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