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5.44
SEL-421 Relay
Instruction Manual
Date Code 20171021
Protection Functions
Ground Directional Element
Reverse Threshold
If Z2R is greater than or equal to 0:
Equation 5.18
If Z2R is less than 0:
Equation 5.19
32V
Directional Calculation
Equation 5.20
Forward Threshold
If Z0F is less than or equal to 0:
Equation 5.21
If Z0F is greater than 0:
Equation 5.22
Reverse Threshold
If Z0R is greater than or equal to 0:
Equation 5.23
If Z0R is less than 0:
Equation 5.24
Z2RTH
0.75
Z2R 0.25
V
2
I
2
------
•
+
•
=
Z2RTH
1.25
Z2R 0.25
V
2
I
2
------
•
+
•
=
z0
Re 3V
0
I
G
1 Z0ANG
•
*
•
I
G
2
---------------------------------------------------------------------------
=
Z0FTH
0.75 Z0F
0.25
3V
0
I
G
---------
•
–
•
=
Z0FTH
1.25 Z0F
0.25
3V
0
I
G
---------
•
–
•
=
Z0RTH
0.75
Z0R 0.25
3V
0
I
G
---------
•
+
•
=
Z0RTH
1.25
Z0R 0.25
3V
0
I
G
---------
•
+
•
=
Summary of Contents for SEL-421-4
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