4.30
SEL-351A Relay
Instruction Manual
Date Code 20080213
Loss-of-Potential, Load Encroachment, and Directional Element Logic
Directional Control for Negative-Sequence and Phase Overcurrent Elements (Not in SEL-351A-1)
Directional Control for Negative-Sequence and
Phase Overcurrent Elements (Not in SEL-351A-1)
The directional control for overcurrent elements is enabled by making
directional control enable setting E32. Setting E32 and other directional
control settings are described in
Directional Control Settings (Not in
.
The negative-sequence voltage-polarized directional element controls the
negative-sequence overcurrent elements. Negative-sequence voltage-polarized
and positive-sequence voltage-polarized directional elements control the
phase overcurrent elements.
gives an overview of how the
negative-sequence voltage-polarized and positive-sequence voltage-polarized
directional elements are enabled and routed to control the negative-sequence
and phase overcurrent elements.
If three-phase voltage signals are not available, make the group setting VNOM
= OFF. This prevents the negative-sequence voltage-polarized and positive-
sequence voltage-polarized elements from operating on false voltage
quantities, yet still allows the Best Choice Ground Directional Element logic
to operate if available. This shut-down logic is shown in the center portions of
Settings for Voltage Input Configuration on
for a complete list of changes caused by setting VNOM = OFF.
q
;
w
;
e
;
r
t
y
u
;
i
;
o
to
;
a
.
Figure 4.19
General Logic Flow of Directional Control for Negative-Sequence and Phase Overcurrent Elements
The negative-sequence voltage-polarized directional element has priority over
the positive-sequence voltage-polarized directional elements in controlling the
phase overcurrent elements. The negative-sequence voltage-polarized
directional element operates for unbalanced faults, while the positive-
sequence voltage-polarized directional element operates for three-phase
faults.
Internal Enables
and
.
The internal enable 32QE corresponds to the negative-sequence voltage-
polarized directional element.
F32P/
R32P
F32Q/
R32Q
q
y
32QE
(Disable)
50QF/
50QR
to Phase Time-
Overcurrent Elements
(
o
)
to Phase
Instantaneous/Definite
Time Overcurrent
Elements
(
a
)
Level 1
32PF/
32PR
Negative-
Sequence
Voltage-
Polarized
w
Positive-
Sequence
Voltage-
Polarized
e
r
32QF/
32QR
t
Level 1
Level 2
Level 3
Level 4
to Negative-Sequence
Instantaneous/Definite
Time Overcurrent
Elements
(
i
)
Level 2
Level 3
Level 4
to Negative-Sequence
Time-Overcurrent
Element (
u
)
Internal
Enables
Relay Word
Bit
Outputs
Relay Word
Bit
Outputs
Relay Word
Bit
Outputs
Directional
Elements
Direction
Forward/
Reverse Logic
Directional
Control
Directional
Element
Routing
Summary of Contents for SEL-351A
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