Schweitzer Engineering Laboratories SEL-751 - Table; Figure 4.26 Negative-Sequence Voltage-Polarized Directional Element for Neutral Ground and Residual Ground Overcurrent Elements

4.39
Date Code 20170927 Instruction Manual SEL-751 Relay
Protection and Logic Functions
Group Settings (SET Command)
q From Table 4.20; w to Figure 4.32 and Figure 4.33; e from Figure 4.23.
Figure 4.26 Negative-Sequence Voltage-Polarized Directional Element for
Neutral Ground and Residual Ground Overcurrent Elements
I
2
V
2
If Z2F Setting > 0, Forward Threshold = 1.25 • Z2F — 0.25 •
I
2
V
2
If Z2F Setting ≤ 0, Forward Threshold = 0.75 • Z2F — 0.25 •
Forward Threshold:
I
2
V
2
If Z2R Setting < 0, Reverse Threshold = 1.25 • Z2R + 0.25 •
I
2
V
2
If Z2R Setting ≥ 0, Reverse Threshold = 0.75 • Z2R + 0.25 •
Reverse Threshold:
Direction Element Characteristics
R2
X2
Forward Threshold
Reverse Threshold
Z2 PLANE
DIRQGE is highest
RDIRQG
(Reverse)
FDIRQG
(Forward)
Best Choice
Ground
Directional
Logic
50QF
Enable
Forward
Threshold
DIRQGE
Reverse
Threshold
50QR
Re[V
2
•(I
2
•1∠Z1ANG)*]
|I
2
|
2
Z2 =
I
2
V
2
Relay
Word
Bits
Relay
Word
Bit
Relay
Word
Bit
Relay
Word
Bit
choice that is asserted
3
1
3
3
2