Schweitzer Engineering Laboratories SEL-351-5, Instruction Manual

Page: 177 / 706

4.33
Date Code 20070117
Instruction Manual SEL-351-5, -6, -7 Relay
Loss-of-Potential, Load Encroachment, and Directional Element Logic
Directional Control for Negative-Sequence and Phase Overcurrent Elements
q To Figure 4.22 .
Figure 4.20 Negative-Sequence Voltage-Polarized Directional Element for
Negative-Sequence and Phase 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
q
R32Q
(Reverse)
F32Q
(Forward)
50QF
Enable
Forward
Threshold
Reverse
Threshold
50QR
Re[V
2
•(I
2
•1
∠
Z1L)*]
|I
2
|
2
Z2 =
I
2
V
2
Relay
Word
Bits
Relay
Word
Bit
32QE
Relay
Word
Bits
Relay
Word
Bit