GE 845, Instruction Manual

Page: 292 / 552

4–164 845 TRANSFORMER PROTECTION SYSTEM – INSTRUCTION MANUAL
PROTECTION CHAPTER 4: SETPOINTS
Phase Instantaneous
Overcurrent
Protection (50P)
The 845 IOC element consists of the equivalent of three separate instantaneous
overcurrent relays (one per phase) - ANSI device 50P - all with identical characteristics. The
settings of this function are applied to each of the three phases to produce Pickup and Trip
flags per phase. There is no intentional “dead band” when the current is above the Pickup
level. However the Pickup accuracy is guaranteed within the current input accuracy of 3%
above the set PKP value. The IOC Pickup flag is asserted, when the current of any phase is
above the PKP value. The IOC Operate flag is asserted if the element stays picked up for the
time defined in PH IOC PKP DELAY. The element drops from Pickup without operating if the
measured current drops below 97-98% of the Pickup value before the time for operation is
reached.
Path :
Setpoints > Protection > Group1(6) > Current > Phase IOC 1(X)
FUNCTION
Range: Disabled, Trip, Alarm, Latched Alarm, Configurable
Default: Disabled
SIGNAL INPUT
Range: Dependant upon the order code
Default: CT Bank 1-J1
This setting provides the selection for the current input bank. The three bank names
listed above are the default and they can be changed in: Setpoints > System > Current
Sensing > [Name] > CT Bank Name.
INPUT
Range: Phasor, RMS
Default: Phasor
PICKUP
Range: 0.050 to 30.000 x CT in steps of 0.001 x CT
Default: 1.000 x CT
DIRECTION
Range: Disabled, Forward (Ph Dir OC 1 FWD), Reverse (Ph Dir OC 1 REV)
Default: Disabled
PICKUP DELAY
Range: 0.000 to 6000.000 s in steps of 0.001 s
Default: 0.000 s
DROPOUT DELAY
Range: 0.000 to 6000.000 s in steps of 0.001 s
Default: 0.000 s
BLOCK
Range: Off, Any FlexLogic operand
Default: Off
OUTPUT RELAY X
For details see Common Setpoints .
EVENTS
Range: Enabled, Disabled
Default: Enabled
TARGETS
Range: Self-reset, Latched, Disabled
Default: Self-reset