Schweitzer Engineering Laboratories SEL-351 - Page 78

iv Overcurrent, Voltage, Synchronism Check, Frequency, and Power Elements Date Code 20001006
SEL-351 Instruction Manual
Figure 3.12: Levels 1 Through 4 Negative-Sequence Instantaneous/Definite-Time Overcurrent
Elements (With Directional Control Option)..............................................................3-15
Figure 3.13: Levels 5 Through 6 Negative-Sequence Instantaneous Overcurrent Elements ...................3-16
Figure 3.14: Phase Time-Overcurrent Element 51PT (With Directional Control Option)......................3-18
Figure 3.15: A-Phase Time-Overcurrent Element 51AT (With Directional Control Option) .................3-22
Figure 3.16: B-Phase Time-Overcurrent Element 51BT (With Directional Control Option)..................3-23
Figure 3.17: C-Phase Time-Overcurrent Element 51CT (With Directional Control Option)..................3-23
Figure 3.18: Neutral Ground Time-Overcurrent Element 51NT (With Directional Control Option) ......3-24
Figure 3.19: Residual Ground Time-Overcurrent Element 51GT (With Directional Control
Option).....................................................................................................................3-26
Figure 3.20: Negative-Sequence Time-Overcurrent Element 51QT (With Directional Control
Option).....................................................................................................................3-27
Figure 3.21: Single-Phase and Three-Phase Voltage Elements (Wye-Connected Voltages) ...................3-33
Figure 3.22: Phase-to-Phase and Sequence Voltage Elements (Wye-Connected Voltages) ....................3-34
Figure 3.23: Phase-to-Phase Voltage Elements (Delta-Connected Voltages).........................................3-35
Figure 3.24: Sequence Voltage Elements (Delta-Connected Voltages)..................................................3-36
Figure 3.25: Channel VS Voltage Elements (Wye- or Delta-Connected Voltages) ................................3-36
Figure 3.26: Synchronism Check Voltage Window and Slip Frequency Elements.................................3-41
Figure 3.27: Synchronism Check Elements..........................................................................................3-42
Figure 3.28: Angle Difference Between V
P
and V
S
Compensated by Breaker Close Time (f
P
< f
S
and V
P
Shown as Reference in This Example)...........................................................3-48
Figure 3.29: Undervoltage Block for Frequency Elements....................................................................3-51
Figure 3.30: Levels 1 Through 6 Frequency Elements .........................................................................3-52
Figure 3.31: Voltage Sag Elements .....................................................................................................3-56
Figure 3.32: Voltage Swell Elements...................................................................................................3-57
Figure 3.33: Voltage Interruption Elements.........................................................................................3-57
Figure 3.34: Power Elements Logic (+VARS Example Shown)...........................................................3-60
Figure 3.35: Power Elements Operation in the Real/Reactive Power Plane...........................................3-61
Figure 3.36: SEL-351(B) Relay Provides VAR Control for 9600 kVAR Capacitor Bank.....................3-62
Figure 3.37: Per Unit Setting Limits for Switching 9600 kVAR Capacitor Bank On- and Off-Line ......3-63
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