Schweitzer Engineering Laboratories SEL-311L, Instruction Manual, Page: 171 / 734

Date Code 20010625 Loss-of-Potential, CCVT Transient Detection, 4-25
Load-Encroachment, and Directional Element Logic
SEL-311L Instruction Manual
a2 Set Automatically
If configuration setting E32 = AUTO, setting a2 is set automatically at:
a2 = 0.1
For setting a2 = 0.1, the negative-sequence current (I
2
) magnitude has to be greater than 1/10 of
the positive-sequence current (I
1
) magnitude in order for the negative-sequence voltage-polarized
directional elements to be enabled (
, , –
).
k2—Zero-Sequence Current Restraint Factor, |I
2
|/|I
0
|
Setting Range:
0.10–1.20 (unitless)
Note the directional enable logic outputs in Figure 4.6:
32QE enable for the negative-sequence voltage-polarized directional element that
controls the phase distance and negative-sequence overcurrent elements
32QGE enable for the negative-sequence voltage-polarized directional element that
controls the ground distance and residual ground overcurrent elements
The k2 factor is applied to enable 32QGE. The negative-sequence current (I
2
) magnitude has to
be greater than the zero-sequence current (I
0
) magnitude multiplied by k2 in order for the 32QGE
enable (and following negative-sequence voltage-polarized directional element in Figure 4.9) to
be enabled:
, N , –
This check assures that the relay uses the most robust analog quantities in making directional
decisions for the ground distance and residual ground overcurrent elements.
If both of the internal enables:
32VE enable for the zero-sequence voltage-polarized directional element that controls
the ground distance and residual ground overcurrent elements
32IE enable for the channel IP current-polarized directional element that controls the
ground distance and residual ground overcurrent elements
are deasserted, then factor k2 is ignored as a logic enable for the 32QGE enable. If neither the
zero-sequence voltage-polarized nor the channel IP current-polarized directional elements are
operable, fewer restrictions (i.e., factor k2) are put on the operation of the negative-sequence
voltage-polarized directional element.
k2 Set Automatically
If configuration setting E32 = AUTO, setting k2 is set automatically at:
k2 = 0.2
For setting k2 = 0.2, the negative-sequence current (I
2
) magnitude has to be greater than 1/5 of the
zero-sequence current (I
0
) magnitude in order for the negative-sequence voltage-polarized