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2-8
Specifications
Date Code 20011026
SEL-321/321-1 Instruction Manual
Phase Voltage Elements
Single-phase and three-phase elements compare individual voltage magnitudes against under-
and overvoltage thresholds.
Zero-Sequence Overvoltage Element
The zero-sequence overvoltage element (59N) is used in the Weak-Infeed logic of the
Permissive-Overreaching Transfer Trip Scheme logic. The 59N element output is also available
for use in the programmable logic.
Positive-Sequence Overvoltage Elements
There are two positive-sequence (V
1
) overvoltage elements: local bus (59PB) and remote bus
(59PR). The 59PB element measures V
1
at the local bus. The 59PR element operates on an
estimate of the voltage at the remote bus. The estimate is V
1
remote = V
1
- a1
⋅
Z
1
L
⋅
I
1
, where Z
1
L
is the positive-sequence replica line impedance, I
1
is the positive-sequence current, and a1 is a
settable scale factor.
Settings Mag. Delay
I
1
Comp.
Zero-Seq. O/V
59N
Bus Phase U/V
27L
Bus Phase O/V
59L
V
1
Local O/V
59PB
59PBD
V
1
Remote O/V
59PR
59PRD
a1
Outputs
1
∅
3
∅
Seq.
Use in Other Logic
Zero-Seq. O/V
59N
Weak-Infeed Logic
Neg.-Seq. O/V
59QL
Loss-of-Potential Logic
Bus Phase U/V
27L
3P27
Weak-Infeed Logic (27L)
Bus Phase O/V
59L
3P59
No
V
1
Voltage
59PL
Loss-of-Potential Logic
V
1
Local O/V
59PB (w/ 59PBD Delay)
No
V
1
Remote O/V
59PR (w/ 59PRD Delay)
No
Supporting Drawings: Figure 2.29 and Figure 2.30.
T
IME
-S
TEP
B
ACKUP
L
OGIC
T
IMERS
Independent timers are provided for Zones 2, 3, and 4 of phase and ground distance protection
and for each level of residual and negative-sequence overcurrent protection.
Timer Settings Phase
21 Gnd
21 67N 67Q
Zone/Level
1
67NL1D
67QL1D
Zone/Level 2
Z2PD
Z2GD
67NL2D
67QL2D
Zone/Level 3
Z3PD
Z3GD
67NL3D
67QL3D
Zone/Level 4
Z4PD
Z4GD
67NL4D
67QL4D
Summary of Contents for SEL-321
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