Schweitzer Engineering Laboratories SEL-311C - Page 153

4.25
Date Code 20060320 Instruction Manual SEL-311C Relay
Loss-of-Potential, CCVT Transient Detection, Load-Encroachment, and Directional Element Logic
Directional Control Settings
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 directional elements to be enabled (|I
2
| >
0.2 • |I
0
|). Again, this presumes at least one of the enables 32VE or 32IE is
asserted.
50GFP—Forward Directional Residual Ground Current Pickup
50GRP—Reverse Directional Residual Ground Current Pickup
Setting Range:
0.25–5.00 A secondary (5 A nominal phase current inputs, IA, IB, IC)
0.05–1.00 A secondary (1 A nominal phase current inputs, IA, IB, IC)
If preceding setting ORDER does not contain V or I (no zero-sequence
voltage-polarized or channel IP current-polarized directional elements are
enabled), then settings 50GFP and 50GRP are not made or displayed.
The 50GFP setting (3I
0
current value) is the pickup for the forward fault
detector 50GF of the zero-sequence voltage-polarized and channel IP
current-polarized directional elements (see Figure 4.7). Ideally, the setting is
above normal load unbalance and below the lowest expected zero-sequence
current magnitude for unbalanced forward faults.
The 50GRP setting (3I
0
current value) is the pickup for the reverse fault
detector 50GR of the zero-sequence voltage-polarized and channel IP current-
polarized directional elements (see Figure 4.7). Ideally, the setting is above
normal load unbalance and below the lowest expected zero-sequence current
magnitude for unbalanced reverse faults.