Schweitzer Engineering SEL-351P - Z0 F - Forward Directional Z0 Threshold; Z0 F and Z0 R Set Automatically; Z0 R - Reverse Directional Z0 Threshold; E32 Iv - Sel Ogic

4-34 Loss-of-Potential, Load Encroachment, and Directional Element Logic Date Code 990430
SEL-351P Manual Técnico
If enable setting E32 = AUTO, setting a0 is set automatically at:
a0 = 0.1
For setting a0 = 0.1, the zero-sequence current (I
0
) magnitude has to be greater than 1/10 of the
positive-sequence current (I
1
) magnitude in order for the zero-sequence voltage-polarized
directional element to be enabled (
II
01
01>⋅.).
Z0F – Forward Directional Z0 Threshold
Z0R – Reverse Directional Z0 Threshold
Setting Range:
-64.00 - 64.00 Ω secondary (5 A nominal phase current inputs, IA, IB, IC)
-320.00 - 320.00 Ω secondary (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 all the
zero-sequence voltage-polarized directional elements (see
Figure SECTION 4: .10 and
Figure SECTION 4: .11).
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:
Z2F = Z0MAG/2 (Ω secondary)
Z2R = Z0MAG/2 + 0.5 (Ω secondary)
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 at least 0.5 Ω secondary greater in
value than setting Z0F.
E32IV – SEL OGIC Control Equation Enable
Refer to Figure SECTION 4: .6.
SEL
OGIC Control Equation setting E32IV must be asserted to logical 1 to enable the zero-
sequence voltage-polarized directional element for directional control of neutral ground and
residual ground overcurrent elements.
Most often, this setting is set directly to logical 1:
E32IV = 1 (numeral 1)
For situations where zero-sequence source isolation can occur (e.g., by the opening of a circuit
breaker) and result in possible mutual coupling problems for the zero-sequence voltage-polarized