6–88
350 FEEDER PROTECTION SYSTEM – INSTRUCTION MANUAL
S3 PROTECTION
CHAPTER 6: SETPOINTS
Figure 6-39: Underfrequency logic diagram
Phase V
oltage Inputs
(associated setpoints)
SETPOINTS
Va
b
SETPOINT
UNDERFREQ FUNCTN:
Disabled = 0
Latched
Alarm
UNDERFREQ PKP:
Vbc
Vca
Operate Output Relay 1 (TRIP)
Event Recorder
Transient Recorder
LED:
TRIP
Alarm
OR
OR
AND
SETPOINTS
Do Not Operate, Operate
OUTPUT
RELA
Y X
Trip
AND
Trip (T
o Breaker Failure)
SETPOINTS
BLOCK 1:
Of
f = 0
BLOCK 2:
Of
f = 0
BLOCK 3:
Of
f = 0
OR
RUN
Va
n
Vbn
Vcn
None
AND
Delta
Wye
LED: PICKUP
Event Recorder
Transient Recorder
Underfrequency1(2)
Message
f < PICKUP
Frequency
Measurement
f ( V
a) - frequency
Va
> Minimum
MIN VOL
TAGE:
SETPOINT
f = 0
UNDERFREQ DELA
Y:
SETPOINT
t
PKP
LED:
ALARM
RESET
Command
AND
S
R
LA
TCH
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