Schweitzer Engineering Laboratories SEL-351 - Page 144

ii Loss-of-Potential, Load Encroachment, and Directional Element Logic Date Code 20001006
SEL-351 Instruction Manual
k2 Set Automatically........................................................................................4-32
50GFP – Forward Directional Residual Ground Current Pickup...............................4-32
50GRP – Reverse Directional Residual Ground Current Pickup ...............................4-32
50GFP and 50GRP Set Automatically..............................................................4-33
a0 – Positive-Sequence Current Restraint Factor, I
0
/I
1
..............................................4-33
a0 Set Automatically........................................................................................4-33
Z0F – Forward Directional Z0 Threshold.................................................................4-34
Z0R – Reverse Directional Z0 Threshold .................................................................4-34
Z0F and Z0R Set Automatically.......................................................................4-34
E32IV – SELOGIC
®
Control Equation Enable..................................................................4-34
Directional Control Provided by Torque Control Settings ........................................................4-35
TABLES
Table 4.1: Overcurrent Elements Controlled by Level Direction Settings DIR1 Through DIR4
(Corresponding Overcurrent Element Figure Numbers in Parentheses).......................4-27
FIGURES
Figure 4.1: Loss-of-Potential Logic.....................................................................................................4-1
Figure 4.2: Load-Encroachment Logic ................................................................................................4-3
Figure 4.3: Migration of Apparent Positive-Sequence Impedance for a Fault Condition........................4-6
Figure 4.4: General Logic Flow of Directional Control for Neutral Ground and Residual Ground
Overcurrent Elements .................................................................................................4-8
Figure 4.5: Internal Enables (32QE and 32QGE) Logic for Negative-Sequence Voltage-Polarized
Directional Elements.................................................................................................4-11
Figure 4.6: Internal Enables (32VE and 32IE) Logic for Zero-Sequence Voltage-Polarized and
Channel IN Current-Polarized Directional Elements ..................................................4-12
Figure 4.7: Best Choice Ground Directional Logic...........................................................................4-13
Figure 4.8: Negative-Sequence Voltage-Polarized Directional Element for Neutral Ground and
Residual Ground Overcurrent Elements.....................................................................4-14
Figure 4.9: Zero-Sequence Voltage-Polarized Directional Element for Neutral Ground and
Residual Ground Overcurrent Elements (see Note 2 Following Figure 4.6) ................4-15
Figure 4.10: Channel IN Current-Polarized Directional Element for Neutral Ground and Residual
Ground Overcurrent Elements (see Note 1 Following Figure 4.6)...............................4-16
Figure 4.11: Routing of Directional Elements to Neutral Ground and Residual Ground
Overcurrent Elements ...............................................................................................4-16
Figure 4.12: Direction Forward/Reverse Logic for Neutral Ground and Residual Ground
Overcurrent Elements ...............................................................................................4-17
Figure 4.13: General Logic Flow of Directional Control for Negative-Sequence and Phase
Overcurrent Elements ...............................................................................................4-18
Figure 4.14: Negative-Sequence Voltage-Polarized Directional Element for Negative-Sequence
and Phase Overcurrent Elements...............................................................................4-21
Figure 4.15: Positive-Sequence Voltage-Polarized Directional Element for Phase Overcurrent
Elements...................................................................................................................4-22
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