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345 TRANSFORMER PROTECTION SYSTEM – INSTRUCTION MANUAL
S3 PROTECTION
CHAPTER 6: SETPOINTS
Figure 20: Percent Differential Protection logic diagram
SETPOINT
Phase
A
current
(IA2d)
SETPOINT
P
ERCENT
DIFF
FUNCTION
:
Disabled
=
0
Latched
Alarm
MINIMUM
PICKUP:
AND
Phase
B
current
(IB2d)
Phase
C
current
(IC
2
d
)
Operate
Output
Relay
1
(W1
BKR
TRIP)
LED:
ALARM
LED:
TRIP
Event
Recorder
T
ransient
Recorder
Alarm
OR
OR
Differential
2nd
Harmonic
AND
SETPOINT
Operate
output
relays
upon
selection
OUTPUT
RELA
Y
4
OUTPUT
RELA
Y
5
OUTPUT
RELA
Y
6
OUTPUT
RELA
Y
3
T
rip
AND
SETPOINT
BLOCK
1:
Of
f
=
0
BLOCK
2:
Of
f
=
0
BLOCK
3:
Of
f
=
0
OR
Message
OR
T
rip
(T
o
Breaker
Failure
)
Phase
A
Dif
f
Current
(IAd)
Differential
Currents
Restraint
Currents
SETPOINT
INRUSH
INHIBIT
FUNCTION
Disabled
=
0
2nd
harmonic
SLOPE
1
BREAKPOINT
1
BREAKPOINT
2
SLOPE
2
INRUSH
INHIBIT
LEVEL
RUN
RUN
RUN
INRUSH
INHIBIT
LEVEL
INRUSH
INHIBIT
MODE
IA2d
=
LEVEL
SETPOINT
RUN
RUN
SETPOINT
OVEREXCIT
A
TION
INHIBIT
FUNCTION
Disabled
=
0
5th
harmonic
=1
Phase
A
current
(IA5d)
Phase
B
current
(I
B5d)
Phase
C
current
(IC5d)
Differential
5th
Harmonic
OVEREXC
INHIBIT
LEVEL
SETPOINT
RUN
RUN
RUN
AND
AND
AND
PCNT
DIFF
PH
C
PKP
Message
Event
Recorder
T
ransient
Recorder
LED:
PICKUP
OR
RESET
Command
AND
S
R
LA
TCH
PCNT
DIFF
PH
AO
P
PCNT
DIFF
PH
B
PKP
PCNT
DIFF
PH
A
PKP
PCNT
DIFF
PKP
RUN
Operate
Output
Relay
2
(W2
BKR
TRIP)
Event
Recorder
2ND
HMNC
DIFF
PH
A
Event
Recorder
Phase
B
Dif
f
Current
(IBd)
Phase
C
Dif
f
Current
(ICd)
Phase
A
Rest
Current
(IAr)
Phase
B
Rest
Current
(IBr)
Phase
C
Rest
Current
(ICr)
IB2d
=
LEVEL
IC2d
=
LEVEL
IA5d
=
LEVEL
IB5d
=
LEVEL
IC5d
=
LEVEL
2ND
HMNC
DIFF
PH
B
2ND
HMNC
DIFF
PH
C
5TH
HMNC
DIFF
PH
A
5TH
HMNC
DIFF
PH
B
5TH
HMNC
DIFF
PH
C
PCNT
DIFF
PH
BO
P
PCNT
DIFF
PH
CO
P
PCNT
DIFF
OP
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