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489 GENERATOR MANAGEMENT RELAY – INSTRUCTION MANUAL
CHAPTER 5: SETPOINTS
For example, given Rated MVA = 100 MVA and Rated Power Factor = 0.85, we have
(EQ 5.28)
5.8.3
Reverse Power
PATH: SETPOINTS
ZV
S7 POWER ELEMENTS
ZV
REVERSE POWER
If enabled, once the magnitude of 3-phase total power exceeds the Pickup Level in the
reverse direction (negative MW) for a period of time specified by the Delay, a trip or alarm
will occur. The level is programmed in per unit of generator rated MW calculated from the
rated MVA and rated power factor. If the generator is accelerated from the power system
rather than the prime mover, the reverse power element may be blocked from start for a
specified period of time. A value of zero for the block time indicates that the reverse power
protection is active as soon as both current and voltage are measured regardless of
whether the generator is online or offline. If the VT type is selected as “None” or VT fuse
loss is detected, the reverse power protection is disabled.
Note
The minimum magnitude of power measurement is determined by the phase CT minimum
of 2% rated CT primary. If the level for reverse power is set below that level, a trip or alarm
will only occur once the phase current exceeds the 2% cutoff.
Rated Mvars
Rated MVA
cos
1
–
Rated PF
(
)
(
)
sin
×
=
100
cos
1
–
0.85
(
)
sin
×
=
52.67 Mvars
=
1 REVERSE
[
Z
]
POWER
BLOCK REVERSE POWER
FROM ONLINE: 1 s
Range: 0 to 5000 s in steps of 1
MESSAGE
REVERSE POWER
ALARM: Off
Range: Off, Latched, Unlatched
MESSAGE
ASSIGN ALARM
RELAYS (2-5): ---5
Range: Any combination of Relays 2 to
5
MESSAGE
REVERSE POWER ALARM
LEVEL: 0.05 x Rated
Range: 0.02 to 0.99
×
Rated MW in
steps of 0.01
MESSAGE
REVERSE POWER ALARM
DELAY: 10.0 s
Range: 0.2 to 120.0 s in steps of 0.1
MESSAGE
REVERSE POWER ALARM
EVENTS: Off
Range: On, Off
MESSAGE
REVERSE POWER
TRIP: Off
Range: Off, Latched, Unlatched
MESSAGE
ASSIGN TRIP
RELAYS (1-4): 1---
Range: Any combination of Relays 1 to
4
MESSAGE
REVERSE POWER TRIP
LEVEL: 0.05 x Rated
Range: 0.02 to 0.99
×
Rated MW in
steps of 0.01
MESSAGE
REVERSE POWER TRIP
DELAY: 20.0 s
Range: 0.2 to 120.0 s in steps of 0.1