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CHAPTER 5: SETPOINTS
489 GENERATOR MANAGEMENT RELAY – INSTRUCTION MANUAL
5–63
Users are cautioned that a reverse power element may not provide reliable indication
when set to a very low setting, particularly under conditions of large reactive loading on
the generator. Under such conditions, low forward power is a more reliable element.
5.8.4
Low Forward Power
PATH: SETPOINTS
ZV
S7 POWER ELEMENTS
ZV
LOW FORWARD POWER
If enabled, once the magnitude of 3-phase total power in the forward direction (+MW) falls
below the Pickup Level for a period of time specified by the Delay, an alarm will occur. The
level is programmed in per unit of generator rated MW calculated from the rated MVA and
rated power factor. The low forward power element is active only when the generator is
online and will be blocked until the generator is brought online, for a period of time defined
by the setpoint Block Low Fwd Power From Online. The pickup level should be set lower
than expected generator loading during normal operations. If the VT type is selected as
“None” or VT fuse loss is detected, the low forward power protection is disabled.
1 LOW FORWARD
[
Z
]
POWER
BLOCK LOW FWD POWER
FROM ONLINE: 0 s
Range: 0 to 15000 s in steps of 1
MESSAGE
LOW FORWARD POWER
ALARM: Off
Range: Off, Latched, Unlatched
MESSAGE
ASSIGN ALARM
RELAYS (2-5): ---5
Range: Any combination of Relays 2 to
5
MESSAGE
LOW FWD POWER ALARM
LEVEL: 0.05 x Rated
Range: 0.02 to 0.99
×
Rated MW in
steps of 0.01
MESSAGE
LOW FWD POWER ALARM
DELAY: 10.0 s
Range: 0.2 to 120.0 s in steps of 0.1
MESSAGE
LOW FWD POWER ALARM
EVENTS: Off
Range: On, Off
MESSAGE
LOW FORWARD POWER
TRIP: Off
Range: Off, Latched, Unlatched
MESSAGE
ASSIGN TRIP
RELAYS (1-4): 1---
Range: Any combination of Relays 1 to
4
MESSAGE
LOW FWD POWER TRIP
LEVEL: 0.05 x Rated
Range: 0.02 to 0.99
×
Rated MW in
steps of 0.01
MESSAGE
LOW FWD POWER TRIP
DELAY: 20.0 s
Range: 0.2 to 120.0 s in steps of 0.1