Sequential Trip - GE 489 Instruction Manual

4 SETPOINTS
The following chart illustrates the Group 2 (alternate group) setpoints
2 S5 SETPOINTS 2 S6 SETPOINTS
CURRENT ELEMENTS VOLTAGE ELEMENTS
2 OVERCURRENT ALARM 2 UNDERVOLTAGE
2 OFFLINE O/C 2 OVERVOLTAGE
2 INADVERTENT ENERG. 2 VOLTS/HERTZ
2 PHASE OVERCURRENT 2 PHASE REVERSAL
2 NEGATIVE SEQUENCE 2 UNDERFREQUENCY
2 GROUND O/C 2 NEUTRAL O/V (Fund)
2 PHASE DIFFERENTIAL 2 NEUTRAL O/V (3rd)
2 GROUND DIRECTIONAL 2 LOSS OF EXCITATION
2 HIGH-SET PHASE O/C 2 DISTANCE ELEMENT
The active group can be selected using the
input will activate the alternate set of protection setpoints, Group 2). In the event of a conflict between the
setpoint or the assigned digital input, Group 2 will be activated. The LED indicator on the faceplate of the 489
POINT GROUP
will indicate when the alternate setpoints are active in the protection scheme. Changing the active setpoint group will be
logged as an event. Independently, the setpoints in either group can be viewed and/or edited using the
setpoint. Headers for each setpoint message subgroup that has dual settings will be denoted by a superscript num-
GROUP
ber indicating which setpoint group is being viewed or edited. Also, when a setpoint that has dual settings is stored, the
flash message that appears will indicate which setpoint group setting has been changed.
PATH: SETPOINTS S3 DIGITAL INPUTS

SEQUENTIAL TRIP

[ENTER] for more
During routine shutdown and for some less critical trips, it may be desirable to use the sequential trip function to prevent
overspeed. If an input is assigned to the sequential trip function, shorting that input will enable either a low forward power or
reverse power function. Once the measured 3-phase total power falls below the low forward power level, or exceeds the
reverse power level for the period of time specified, a trip will occur. This time delay will typically be shorter than that used
for the standard reverse power or low forward power elements. The level is programmed in per unit of generator rated MW
calculated from the rated MVA and rated power factor. If the VT type is selected as None, the sequential trip element will
operate as a simple timer. Once the input has been shorted for the period of time specified by the delay, a trip will occur.
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.
NOTE
Users are cautioned that a reverse power element may not provide reliable indication when set to a very low setting, partic-
ularly under conditions of large reactive loading on the generator. Under such conditions, low forward power is a more reli-
able element.
GE Multilin
2 S7 SETPOINTS
POWER ELEMENTS
2 REACTIVE POWER
2 REVERSE POWER
2 LOW FORWARD POWER
ACTIVATE SETPOINT GROUP
SEQUENTIAL TRIP
ð
ASSIGN DIGITAL
ENTER
ð
ESCAPE INPUT: None
SEQUENTIAL TRIP TYPE
ESCAPE
Low Forward Power
MESSAGE
ASSIGN TRIP
ESCAPE
RELAYS (1-4): 1---
MESSAGE
SEQUENTIAL TRIP
ESCAPE
LEVEL: 0.05 x Rated MW
MESSAGE
SEQUENTIAL TRIP
ESCAPE
DELAY: 1.0 s
MESSAGE
489 Generator Management Relay
4.4 S3 DIGITAL INPUTS
2 S8 SETPOINTS 2 S9 SETPOINTS
RTD TEMPERATURE
2 RTD TYPES 2 MODEL SETUP
2 RTD #1 2 THERMAL ELEMENTS
↓
2 RTD #12
2 OPEN RTD SENSOR
2 RTD SHORT/LOW TEMP
setpoint or the assigned digital input (shorting that
4.4.8 SEQUENTIAL TRIP
Range: None, Input 1 to Input 7. If an input is assigned to
the Tachometer, it may not be used here.
Range: Low Forward Power, Reverse Power
Range: Any combination of Relays 1 to 4
Range: 0.02 to 0.99 × Rated MW in steps of 0.01
Range: 0.2 to 120.0 s in steps of 0.1
THERMAL MODEL
ACTIVATE SET-
4
EDIT SETPOINT
4-17