4-18
Loss-of-Potential, Load Encroachment, and Directional Element Logic
Date Code 20001006
SEL-351 Instruction Manual
D
IRECTIONAL
C
ONTROL FOR
N
EGATIVE
-S
EQUENCE AND
P
HASE
O
VERCURRENT
E
LEMENTS
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 the following
subsection
Directional Control Settings
.
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. Figure 4.13 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.
Figure 4.13: 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
Refer to Figure 4.5 and Figure 4.13.
The internal enable 32QE corresponds to the negative-sequence voltage-polarized directional
element.
Note that Figure 4.5 has extra internal enable 32QGE, which is used in the directional element
logic that controls the neutral ground and residual ground overcurrent elements (see Figure 4.4).
The settings involved with internal enable 32QE in Figure 4.5 (e.g., settings a2, k2) are explained
in a following subsection
Directional Control Settings
.
Summary of Contents for SEL-351
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