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CHAPTER 5: SETPOINTS
489 GENERATOR MANAGEMENT RELAY – INSTRUCTION MANUAL
5–27
One of assignable digital inputs 4 to 7 may be assigned to the tachometer function to
measure mechanical speed. The time between each input closure is measured and
converted to an RPM value based on one closure per revolution. If an overspeed trip or
alarm is enabled, and the measured RPM exceeds the threshold setpoint for the time
specified by the delay, a trip or alarm will occur. The RPM value can be viewed with the
A2
METERING DATA
ZV
SPEED
ZV
TACHOMETER
actual value.
For example, an inductive proximity probe or hall effect gear tooth sensor may be used to
sense the key on the generator. The probe could be powered from the +24V from the digital
input power supply. The NPN transistor output could be taken to one of the assignable
digital inputs assigned to the tachometer function.
5.4.11 Waveform Capture
PATH: SETPOINTS
ZV
S3 DIGITAL INPUTS
ZV
WAVEFORM CAPTURE
If an input is assigned to the tachometer function, it may not be used here.
This feature may be used to trigger the waveform capture from an external contact. When
one of the inputs is assigned to the Waveform Capture function, shorting that input will
trigger the waveform.
5.4.12 Ground Switch Status
PATH: SETPOINTS
ZV
S3 DIGITAL INPUTS
ZV
GND SWITCH STATUS
If an input is assigned to the tachometer function, it may not be used here.
This function is used to detect the status of a grounding switch for the generator for which
the relay is installed. Refer to
on page A–1 for additional details.
MESSAGE
TACHOMETER TRIP
SPEED: 110% Rated
Range: 101 to 175% in steps of 1
MESSAGE
TACHOMETER TRIP
DELAY: 1 s
Range: 1 to 250 s in steps of 1
WAVEFORM
[
Z
]
ASSIGN DIGITAL
INPUT: None
Range: None, Input 1 to Input 7.
GROUND
[
Z
]
ASSIGN DIGITAL
INPUT: None
Range: None, Input 1 to Input 7
MESSAGE
GROUND SWITCH
CONTACT: Auxiliary a
Range: Auxiliary a, Auxiliary b