4-28 Loss-of-Potential, Load Encroachment, and Directional Element Logic Date Code 20001006
SEL-351 Instruction Manual
In some applications, level direction settings DIR1 through DIR4 are not flexible enough in
assigning the desired direction for certain overcurrent elements. Subsection Directional Control
Provided by Torque Control Settings at the end of this section describes how to avoid this
limitation for special cases.
ORDER – Ground Directional Element Priority Setting
Setting Range:
Q Negative-sequence voltage-polarized directional element
V Zero-sequence voltage-polarized directional element
I Channel IN current-polarized directional element
OFF No ground directional control
Setting ORDER can be set with any combination of Q, V, and I. The order in which these
directional elements are listed in setting ORDER determines the priority in which they operate to
provide Best Choice Ground Directional logic control. See Figure 4.7.
Note 1: If channel IN is rated 0.05 A nominal, then setting option “I” is not available for setting
ORDER. This results in internal enable 32IE defaulting to logical 0 at the bottom of
Figure 4.6. The channel IN current-polarized directional element that follows in
Figure 4.10 is defeated and nonoperational when internal enable 32IE = logical 0.
Thus, the channel IN current-polarized directional element in Figure 4.10 is defeated,
nonoperational, and unavailable when channel IN is rated 0.05 A nominal.
Note 2: If the voltage inputs are delta-connected, then setting option “V” is not available for
setting ORDER. This results in internal enable 32VE defaulting to logical 0 (see middle
of Figure 4.6). The zero-sequence voltage-polarized directional element that follows in
Figure 4.9 is defeated and nonoperational when internal enable 32VE = logical 0.
Thus, the zero-sequence voltage-polarized directional element in Figure 4.9 is defeated,
nonoperational, and unavailable when the voltage inputs are delta-connected (see Figures
1.2 and 1.3).
For example, if setting:
ORDER = QV
then the first listed directional element (Q = negative-sequence voltage-polarized directional
element; see Figure 4.8) is the first priority directional element to provide directional control for the
neutral ground and residual ground overcurrent elements.
If the negative-sequence voltage-polarized directional element is not operable (i.e., it does not have
sufficient operating quantity as indicated by its internal enable, 32QGE, not being asserted), then
the second listed directional element (V = zero-sequence voltage-polarized directional element; see
Figure 4.9) provides directional control for the neutral ground and residual ground overcurrent
elements.
Courtesy of NationalSwitchgear.com
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