4.26
SEL-351A Relay
Instruction Manual
Date Code 20080213
Loss-of-Potential, Load Encroachment, and Directional Element Logic
Directional Control for Neutral-Ground and Residual-Ground Overcurrent Elements (Not in SEL-351A-1)
q
and
w
Figure 4.14
Zero-Sequence Voltage-Polarized Directional Element
(Ungrounded/High-Impedance Grounded Systems)
The 3V
0
may be either a calculated value (when global
settings VSCONN = VS and PTCONN = WYE) or a measured value (when
global setting VSCONN = 3V0). See
Zero-Sequence Voltage Sources on
I
N
3V
0
Z0F = —0.10, Forward Threshold = 0.75 • Z0F — 0.25 •
Forward Threshold:
I
N
3V
0
Z0R = 0.10, Reverse Threshold = 0.75 • Z0R + 0.25 •
Reverse Threshold:
Note: 1
∠
90˚ = One Ohm at —90˚ Angle
For setting ORDER = U, settings Z0F and Z0R are set internally, as shown above, and hidden.
Direction Element Characteristics
R0
X0
Forward Threshold
Reverse Threshold
Z0 PLANE
w
R32N
F32N
Forward
Reverse
ORDER = U
50NF
Enable
Forward
Threshold
32NE
Reverse
Threshold
50NR
Re[3V
0
•(I
N
•1
∠
90˚)*]
|I
N
|
2
Z0 =
I
N
3V
0
Relay
Word
Bits
Relay
Word
Bit
Relay
Word
Bit
Relay
Word
Bit
"Forward"
Outputs
q
"Reverse"
Outputs
q
Summary of Contents for SEL-351A
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