Schweitzer Engineering SEL-351P, Quick Start Manual

Page: 255 / 674

Date Code 990430 Loss-of-Potential, Load Encroachment, and Directional Element Logic 4-33
SEL-351P Manual Técnico
50GFP – Forward Directional Residual Ground Current Pickup
50GRP – Reverse Directional Residual Ground Current Pickup
Setting Range:
0.05 - 1.00 A secondary (1 A nominal phase current inputs, IA, IB, IC)
If preceding setting ORDER does not contain V (zero-sequence voltage-polarized directional
element is not 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, residual-current directional element (see Figure SECTION 4:
.6). 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, residual-current directional element (see Figure SECTION 4:
.6). Ideally, the setting is above normal load unbalance and below the lowest expected zero-
sequence current magnitude for unbalanced reverse faults.
The 50GFP/10 setting (I
N
current value) is the pickup for the forward fault detector 50NF of the
zero-sequence voltage-polarized, neutral-current directional element (see Figure SECTION 4:
.7). This setting is always automatic and used for SEF applications.
The 50GRP/10 setting (I
N
current value) is the pickup for the reverse fault detector 50NR of the
zero-sequence voltage-polarized, neutral-current directional element (see Figure SECTION 4:
.7). This setting is always automatic and used for SEF applications.
50GFP and 50GRP Set Automatically
If enable setting E32 = AUTO, settings 50GFP and 50GRP are set automatically at:
50GFP = 0.10 A secondary (1 A nominal phase current inputs, IA, IB, IC)
50GRP = 0.05 A secondary (1 A nominal phase current inputs, IA, IB, IC)
a0 – Positive-Sequence Current Restraint Factor, I
0
/I
1
Setting Range:
0.02 - 0.50 (unitless)
If preceding setting ORDER does not contain V (zero-sequence voltage-polarized directional
element is not enabled), then setting a0 is not made or displayed.
Refer to Figure SECTION 4: .6.
The a0 factor increases the security of the zero-sequence voltage-polarized directional element.
It keeps the element from operating for zero-sequence current (system unbalance), which
circulates due to line asymmetries, CT saturation during three-phase faults, etc.
a0 Set Automatically