GE 889 - Sequential Shutdown

CHAPTER 4: SETPOINTS CONTROL
889 GENERATOR PROTECTION SYSTEM – INSTRUCTION MANUAL 4–337
Sequential Shutdown During routine shutdown and for less critical trips, it may be desirable to use the sequential
shutdown function to prevent overspeed. Any FlexLogic operand (e.g. Digital Inputs) can be
assigned as arming input to enable this function. The arming input enables either a low
forward power or reverse power function, based on the power direction setting selection.
Once the measured 3-phase total power falls below the forward power level or exceeds
the reverse power level for the period of specified time, a trip will occur. This time delay will
typically be shorter than that used for standard reverse power or low forward power
elements. The level is programmed per unit of generator rated MW calculated from the
rated MVA and rated power factor.
NOTE
NOTE:
A reverse power element may not be suitable when set to a very low setting, particularly
under conditions of large reactive loading on the generator. Under such conditions, low
forward power is recommended.
Path: Setpoints > Control > Generator > Sequential Shutdown
FUNCTION
Range: Disabled, Trip, Alarm, Latched Alarm, Configurable
Default: Disabled
ARMING INPUT
Range: Off, Any FlexLogic operand
Default: Off
This setting selects a specific arming input from FlexLogic operands. Normally,
sequential shutdown is armed/initiated from digital input (from an external device).
NOTE
NOTE:
NOTE: The Arming Input should remain ON/latched until the sequential shutdown
operation is executed.
POWER DIRECTION
Range: Forward, Reverse
Default: Forward
This setting provides options for the direction of power flow.
PICKUP MW LEVEL
Range: 0.02 to 0.99 x Rated in steps of 0.01
Default: 0.05 x Rated
When the measured 3-phase total power falls below the setting of the forward pickup
power level, or exceeds the reverse power pickup level for the period of time specified,
an OP operant is issued.
PICKUP DELAY
Range: 0.20 to 180.00 s in steps of 0.01 s
Default: 10.00 s
OUTPUT DELAY
Range: Do Not Operate, Operate
Default: Do Not Operate
BLOCK
Range: Off, Any FlexLogic operand
Default: Off
EVENT:
Range: Enabled, Disabled
Default: Disabled