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5.130
SEL-421 Relay
Instruction Manual
Date Code 20171021
Protection Functions
Permissive Overreaching Transfer Tripping Scheme
Figure 5.94
POTT Logic Diagram
0
Z3RBD
0
EBLKD
ETDPU
0
0
EDURD
R
eset
0
1/
8
CY
C
1/
8
CY
C
ETDPU + EDURD + 1 C
YCLE
0
0
—
+
—
+
—
+
—
+
Z3RB
KEY
KEYD
EKEY
EC
TT
WF
C
R
ela
y
Wo
rd
Bits
IL
OP
Z3P
Z3G
67G3
67Q3
3PO
EL
OP := Y1
TR
COMMD
COMZD
TC
TR
COMM
R
ela
y
Wo
rd
Bits
PT
EPO := 5
2
3PT
VA
B
VBC
VC
A
27PP
W := 80
3 • V
O
59NW := 5
R
ela
y
Wo
rd
Bit
R
ela
y
Wo
rd
Bits
R
ela
y
Wo
rd
Bits
SEL
OGIC
Set
ting
Set
ting
Set
ting
EBLKD := OFF
ETDPU := OFF
Set
tings
Set
ting
Set
tings
EWF
C := Y
, SP
—
+
VA
27
AW
I
—
+
27
BW
I
VB
—
+
27
CW
I
VC
27P
WI := 4
7
Set
ting
Summary of Contents for SEL-421-4
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