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5–48
489 GENERATOR MANAGEMENT RELAY – INSTRUCTION MANUAL
CHAPTER 5: SETPOINTS
The formula for Volts/Hertz Curve 3 is:
(EQ 5.22)
where:
T
= trip time in seconds
D
=
VOLTS/HERTZ TRIP DELAY
setpoint
V
= RMS measurement of Vab
F
= frequency of Vab
V
NOM
= generator voltage setpoint
F
S
= generator frequency setpoint
Pickup =
VOLTS/HERTZ TRIP PICKUP
setpoint
The V/Hz Curve 3 trip curves are shown below for delay settings of 0.1, 0.3, 1, 3, and 10
seconds.
Note
Volts/Hertz is calculated per unit as follows:
5.7.4
Phase Reversal
PATH: SETPOINTS
ZV
S6 VOLTAGE ELEM.
ZV
PHASE REVERSAL
The 489 can detect the phase rotation of the three phase voltages. A trip will occur within
200 ms if the Phase Reversal feature is turned on, the generator is offline, each of the
phase-phase voltages is greater than 50% of the generator rated phase-phase voltage
T
D
V F
⁄
V
nom
F
s
⁄
(
)
Pickup
×
--------------------------------------------------
⎝
⎠
⎛
⎞
0.5
1
–
-----------------------------------------------------------------------
=
, when
V
F
---
Pickup
>
808743A1-X3.CDR
0.1
1
10
100
1000
10000
1.00
1.20
1.40
1.60
1.80
2.00
Multiples of Voltz/Hertz Pickup
10
3
1
0.3
TIME
DELA
Y
SETTING
0.1
T
ime
to
T
rip
(seconds)
Volts/Hertz
phase-phase voltage rated phase-phase voltage
⁄
frequency rated frequency
⁄
-----------------------------------------------------------------------------------------------------------------------------
=
1 PHASE
[
Z
]
REVERSAL
PHASE REVERSAL
TRIP: Off
Range: Off, Latched, Unlatched
MESSAGE
ASSIGN TRIP
RELAYS (1-4): 1---
Range: Any combination of Relays 1 to
4