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Date Code 20170927 Instruction Manual SEL-751 Relay
List of Figures
Figure 4.13 U.S. Extremely Inverse Curve: U4....................................................................................... 4.24
Figure 4.14 U.S. Short-Time Inverse Curve: U5 .....................................................................................4.25
Figure 4.15 IEC Class A Curve (Standard Inverse): C1.......................................................................... 4.25
Figure 4.16 IEC Class B Curve (Very Inverse): C2................................................................................. 4.25
Figure 4.17 IEC Class C Curve (Extremely Inverse): C3........................................................................ 4.25
Figure 4.18 IEC Long-Time Inverse Curve: C4 ...................................................................................... 4.26
Figure 4.19 IEC Short-Time Inverse Curve: C5......................................................................................4.26
Figure 4.20 General Logic Flow of Directional Control for Neutral Ground and Residual Ground
Overcurrent Elements (Excluding Ungrounded/High-Impedance
Grounded Systems)........................................................................................................... 4.27
Figure 4.21 General Logic Flow of Directional Control for Neutral Ground and Residual
Ground Overcurrent Elements (Ungrounded/High-Impedance Grounded Systems;
ORDER := U) ................................................................................................................... 4.28
Figure 4.22 Logic for Relay Word bit GNDSW...................................................................................... 4.32
Figure 4.23 Internal Enables (DIRQE and DIRQGE) Logic for Negative-Sequence
Voltage-Polarized Directional Elements........................................................................... 4.36
Figure 4.24 Internal Enables (DIRVE and DIRIE) Logic for Zero-Sequence Voltage-Polarized
and Channel IN Current-Polarized Directional Elements ................................................ 4.37
Figure 4.25 Internal Enable (DIRNE) Logic for Zero-Sequence Voltage-Polarized Directional
Elements (Low-Impedance Grounded, Petersen Coil-Grounded, and
Ungrounded/High-Impedance Grounded Systems).......................................................... 4.38
Figure 4.26 Negative-Sequence Voltage-Polarized Directional Element for Neutral Ground
and Residual Ground Overcurrent Elements .................................................................... 4.39
Figure 4.27 Zero-Sequence Voltage-Polarized Directional Element....................................................... 4.40
Figure 4.28 Channel IN Current-Polarized Directional Element ............................................................ 4.41
Figure 4.29 Zero-Sequence Voltage-Polarized Directional Element (Low-Impedance
Grounded Systems)........................................................................................................... 4.42
Figure 4.30 Wattmetric and Incremental Conductance Directional Elements (Petersen
Coil-Grounded Systems) .................................................................................................. 4.43
Figure 4.31 Zero-Sequence Voltage-Polarized Directional Element (Ungrounded/High-Impedance
Grounded Systems)........................................................................................................... 4.44
Figure 4.32 Routing of Directional Elements to Residual Ground Overcurrent Elements ..................... 4.45
Figure 4.33 Routing of Directional Elements to Neutral Ground Overcurrent Elements ....................... 4.45
Figure 4.34 Direction Forward/Reverse Logic for Residual Ground Overcurrent Elements .................. 4.46
Figure 4.35 Direction Forward/Reverse Logic for Neutral Ground Overcurrent Elements .................... 4.47
Figure 4.36 General Logic Flow of Directional Control for Negative-Sequence and Phase
Overcurrent Elements ....................................................................................................... 4.48
Figure 4.37 Negative-Sequence Voltage-Polarized Directional Element for Negative-Sequence
and Phase Overcurrent Elements...................................................................................... 4.50
Figure 4.38 Positive-Sequence Voltage-Polarized Directional Element for Phase Overcurrent
Elements ........................................................................................................................... 4.51
Figure 4.39 Routing of Directional Elements to Negative-Sequence and Phase Overcurrent
Elements ........................................................................................................................... 4.52
Figure 4.40 Direction Forward/Reverse Logic for Negative-Sequence Overcurrent Elements .............. 4.52
Figure 4.41 Direction Forward/Reverse Logic for Phase Overcurrent Elements.................................... 4.53
Figure 4.42 Traditional Channel IN Current-Polarized Directional Element.......................................... 4.61
Figure 4.43 Current-Polarized Directional Element Characteristic When INMTA 0.00 ..................... 4.62
Figure 4.44 Zero-Sequence Impedance Network and Relay Polarity ..................................................... 4.64
Figure 4.45 Zero-Sequence Impedance Plot for Solidly-Grounded, Mostly Inductive System.............. 4.64
Figure 4.46 Low-Impedance Grounded Distribution System With a Ground Fault on Feeder 1............ 4.65
Figure 4.47 Zero-Sequence Impedance Network for Low-Impedance Grounded Distribution
System With a Ground Fault on Feeder 1......................................................................... 4.66
Figure 4.48 Decreasing Neutral Resistance R
G
Results in Increasing Zero-Sequence Current I
OG
....... 4.67
Figure 4.49 Decreasing Neutral Resistance R
G
Results in Increasing Zero-Sequence Current I
0(1)
(Seen by Relay 1) ............................................................................................................. 4.67
Figure 4.50 Zero-Sequence Impedance Plots for Ground Fault on Low-Impedance
Grounded Distribution System ......................................................................................... 4.68
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