4.57
Date Code 20170927 Instruction Manual SEL-751 Relay
Protection and Logic Functions
Group Settings (SET Command)
In some applications, level direction settings DIR1 through DIR4 are not flex-
ible enough in assigning the desired direction for certain overcurrent elements.
Directional Control Provided by Torque Control Settings on page 4.77
describes how to avoid this limitation for special cases.
ORDER—Ground Directional Element Priority Setting
Setting ORDER can be set with the elements listed and defined in Tab le 4.19,
subject to the setting combination constraints in Table 4.20 and Table 4.21.
Note that Table 4.19 and Tab le 4.20 also list directional element availability
per model (according to the neutral channel [IN] rating). Table 4.2 1 lists the
ground directional element availability as a result of the voltage connection
settings.
The order in which the directional elements are listed in setting ORDER
determines the priority in which these elements operate to provide Best
Choice Ground Directional Element logic control.
For example, if setting:
ORDER = QVS
then the first listed directional element (Q = negative-sequence voltage-polar-
ized directional element; see Figure 4.26) is the first priority directional ele-
ment 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, DIRQGE, not being asserted; see Figure 4.23), then the second listed
directional element (V = zero-sequence voltage-polarized directional element;
see Figure 4.27) provides directional control for the neutral ground and resid-
ual ground overcurrent elements.
If the zero-sequence voltage-polarized directional element is not operable
(i.e., it does not have sufficient operating quantity as indicated by its internal
enable, DIRVE, not being asserted; see Figure 4.24), then the third listed
directional element (S = zero-sequence voltage-polarized directional element
[low-impedance]; see Figure 4.29) provides directional control for the neutral
ground and residual ground overcurrent elements.
If the zero-sequence voltage-polarized directional element (low-impedance) is
not operable (i.e., it does not have sufficient operating quantity as indicated by
its internal enable, DIRNE [low-impedance], not being asserted; see
Figure 4.25), then no directional control is available. The neutral ground and
residual ground overcurrent elements will not operate, even though these ele-
ments are designated with the DIRn (n = 1–4) settings to be directionally con-
trolled (see Figure 4.34 and Figure 4.35).
Another example, if setting:
ORDER = V
then the zero-sequence voltage-polarized directional element (V = zero-
sequence voltage-polarized directional element; see Figure 4.27) provides
directional control for the neutral ground and residual ground overcurrent ele-
ments at all times (assuming it has sufficient operating quantity). If there is not
sufficient operating quantity during an event (i.e., internal enable DIRVE is
not asserted; see Figure 4.24), then no directional control is available. The
neutral ground and residual ground overcurrent elements will not operate,
even though these elements are designated with the DIRn (n = 1–4) settings to
be directionally controlled (see Figure 4.34 and Figure 4.35).
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