Schweitzer Engineering Laboratories SEL-351 - Z0 F - Forward Directional Z0 Threshold; Z0 F and Z0 R Set Automatically; Z0 R - Reverse Directional Z0 Threshold; E32 IV - SEL OGIC Control Equation Enable

4-34 Loss-of-Potential, Load Encroachment, and Directional Element Logic Date Code 20001006
SEL-351 Instruction Manual
Z0F – Forward Directional Z0 Threshold
Z0R – Reverse Directional Z0 Threshold
Setting Range:
-64.00 to 64.00 W secondary (150 V voltage inputs, VA, VB, VC; 5 A nominal phase current
inputs, IA, IB, IC)
-320.00 to 320.00 W secondary (150 V voltage inputs, VA, VB, VC; 1 A nominal phase
current inputs, IA, IB, IC)
-128.00 to 128.00 W secondary (300 V voltage inputs, VA, VB, VC; 5 A nominal phase
current inputs, IA, IB, IC)
-640.00 to 640.00 W secondary (300 V voltage inputs, VA, VB, VC; 1 A nominal phase
current inputs, IA, IB, IC)
If preceding setting ORDER does not contain V (no zero-sequence voltage-polarized directional
element is enabled), then settings Z0F and Z0R are not made or displayed.
Z0F and Z0R are used to calculate the Forward and Reverse Thresholds, respectively, for the zero-
sequence voltage-polarized directional elements (see Figure 4.9).
Z0F and Z0R Set Automatically
If enable setting E32 = AUTO, settings Z0F and Z0R (zero-sequence impedance values) are
calculated automatically, using the zero-sequence line impedance magnitude setting Z0MAG as
follows:
Z0F = Z0MAG/2 (W secondary)
Z0R = Z0MAG/2 + z (W secondary; “z” listed in table below)
If enable setting E32 = Y, settings Z0F and Z0R (zero-sequence impedance values) are calculated
by the user and entered by the user, but setting Z0R must be greater in value than setting Z0F by
value “z”:
Relay Configuration z (W secondary)
5 A nominal current, 150 V voltage inputs 0.1
5 A nominal current, 300 V voltage inputs 0.2
1 A nominal current, 150 V voltage inputs 0.5
1 A nominal current, 300 V voltage inputs 1.0
E32IV – SELOGIC Control Equation Enable
Refer to Figure 4.6.
SELOGIC Control Equation setting E32IV must be asserted to logical 1 to enable the zero-sequence
voltage-polarized and channel IN current-polarized directional elements for directional control of
neutral ground and residual ground overcurrent elements.
Courtesy of NationalSwitchgear.com