GE 845 - Page 359

CHAPTER 4: SETPOINTS PROTECTION
845 TRANSFORMER PROTECTION SYSTEM – INSTRUCTION MANUAL 4–231
Figure 4-89: Underfrequency Protection logic diagram
LED: PICKUP
Current Inputs
Phase A Current (IA) Phase B Current (IB)
Phase C Current (IC)
SETPOINTS
BLOCK : Off=0
AND
SETPOINTS
UNDERFREQ 1 FUNCTION : Disabled Trip Alarm Latched Alarm Configurable
OR
None
Positive -
sequence
SETPOINTS
UNDERFREQ 1 MINIMUM CURRENT : I = MINIMUM
SETPOINTS
UNDERFREQ 1 MINIMUM VOLTAGE :
AND
SETPOINTS
UNDERFREQ 1 PICKUP : 0 < f = PICKUP
FREQUENCY f
RUN
SETPOINTS
UNDERFREQ 1 PICKUP DELAY : t
PKP
t
DPO
UNDERFREQ 1 DROPOUT DELAY :
Underfreq 1 OP
FlexLogic Operands
Underfreq 1 PKP
AN D AND AND
Command
RESET
OR
LED: ALARM
LED: TRIP
Operate Output Relay 1 (TRIP)
WYE DELTA
VA
VAB
VB VBC VC VCA
Vx
RUN
V = MINIMUM RUN
SETPOINTS
OUTPUT RELAY 3 (X) Do Not Operate , Operate
S
LATCH
Set-
Dominant
R
SETPOINTS
UNDERFREQ 1 SIGNAL INPUT
:
Positive-
sequence
Composite
Voltage Inputs
892737A3.cdr