Overview21
Relay Mounting21
Figure 2.1 SEL-551 Dimensions, Panel Cutout, and Drill Plan22
Figure 2.2 Relay Dimensions and Drill Plan for Mounting Two SEL-500 Series Relays Together Using Mounting Block (SEL P/N 9101)23
Figure 2.3 Relay Dimensions and Drill Plan for Mounting an SEL-551 with Rack Mount Bracket 9100 (Bracket on Right Side in Front View)24
Figure 2.4 SEL-551 Fitted with Mounting Bracket (SEL P/N 9100) for Mounting in 19-Inch Rack24
Rear-Panel Connections25
Figure 2.5 SEL-551 Front Panel, Rack-Mount Version (Half-Rack Width)25
Figure 2.6 SEL-551 Front Panel, Panel-Mount Version25
Figure 2.7 SEL-551 Rear Panel (Conventional Terminal Blocks Option)26
Figure 2.8 SEL-551 Rear Panel (Plug-In Connectors Option)27
AC/DC Connection Diagrams for Example Applications29
Figure 2.9 SEL-551 Provides Overcurrent Protection and Reclosing for a Utility Distribution Feeder (Includes Fast Bus Trip Scheme)29
Figure 2.10 SEL-551 Provides Overcurrent Protection for an Industrial Distribution Feeder (Core-Balance Current Transformer Connected to Current Input Channel IN)30
Figure 2.11 SEL-551 Provides Overcurrent Protection for a Delta-Wye Transformer Bank31
Figure 2.12 SEL-551 Provides Overcurrent Protection for a Transformer Bank with a Tertiary Winding32
Figure 2.13 SEL-551 Provides Overcurrent Protection for a Distribution Bus (Includes Fast Bus Trip Scheme)33
EIA-485 Rear-Panel Adapter34
Figure 2.14 SEL-551 Provides Dedicated Breaker Failure Protection34
Circuit Board Jumpers and Battery35
Table 2.1 Required Control Voltage Jumper Positions for Applied Nominal Control Voltage (SEL-551 with the Conventional Terminal Blocks Option)35
Figure 2.15 Input and Output Jumper Locations (SEL-551 Relay with the Conventional Terminal Blocks with Jumper-Selectable Control Input Voltage Option)36
Table 2.2 Required Position of Jumper JMP13 for Desired Output Contact OUT4 Operation37
Figure 2.16 Output Contact OUT4 Control Jumper Location37
Section 3: Relay Elements and Logic Relay Word Bits and SEL OGIC Control Equations40
- Optoisolated Inputs41
- Table 3.2 Processing Order of Relay Elements and Logic (Top to Bottom)41
- Figure 3.1 Example Operation of SEL-551 Optoisolated Inputs41
- Local Control Switches43
- Table 3.3 Correspondence between Local Control Switch Positions and Label Settings43
- Figure 3.2 Local Control Switches Drive Local Bits LB1-LB843
- Table 3.4 Correspondence between Local Control Switch Types and Required Label Settings44
- Remote Control Switches45
- Instantaneous Overcurrent Elements46
- Figure 3.3 Remote Control Switches Drive Remote Bits RB1-RB846
- Figure 3.4 Phase Instantaneous Overcurrent Elements 50P1-50P647
- Figure 3.5 Single-Phase Instantaneous Overcurrent Elements 50A, 50B, and 50C48
- Figure 3.6 Neutral Ground Instantaneous Overcurrent Elements 50N1 and 50N248
- Figure 3.7 Residual Ground Instantaneous Overcurrent Elements 50G1 and 50G249
- Figure 3.8 Negative-Sequence Instantaneous Overcurrent Elements 50Q1 and 50Q249
- Time-Overcurrent Elements50
- Figure 3.9 Phase Time-Overcurrent Elements 51P1T and 51P2T50
- Figure 3.10 Neutral Ground Time-Overcurrent Element 51N1T53
- Figure 3.11 Residual Ground Time-Overcurrent Element 51G1T53
- Figure 3.12 Negative-Sequence Time-Overcurrent Elements 51Q1T and 51Q2T54
- Trip Logic55
- Figure 3.13 Trip Logic55
- Close Logic58
- Figure 3.14 Close Logic58
- Reclosing Relay60
- Figure 3.15 Reclosing Relay States and General Operation60
- Table 3.5 Relay Word Bit and Front-Panel Correspondence to Reclosing Relay States61
- Figure 3.16 Reclosing Sequence from Reset to Lockout with Factory Settings63
- Table 3.6 Shot Counter Correspondence to Relay Word Bits and Open Interval Times65
- Figure 3.17 Voltage Relay (27/59) Provides Reclose Block Signal to SEL-55170
- Figure 3.18 Sequence Coordination between the SEL-551 and a Line Recloser73
- Figure 3.19 Operation of SEL-551 Shot Counter for Sequence Coordination with Line Recloser (Additional Settings Example 1)73
- Figure 3.20 Operation of SEL-351 Relay Shot Counter for Sequence Coordination with Line Recloser (Additional Setting Example 2)75
- SEL OGIC Control Equation Variables/Timers76
- Output Contacts77
- Figure 3.23 Logic Flow for Example SEL-551 Output Contact Operation78
- Demand Ammetering79
- Figure 3.24 Response of Thermal Demand Ammeter to a Step Input (Setting DMTC = 15 Minutes)80
- Table 3.7 Demand Ammeter Settings and Settings Range81
- Figure 3.26 Demand Current Logic Outputs82
- Figure 3.27 Raise Pickup of Residual Ground Time-Overcurrent Element for Unbalance Current83
- Front-Panel Target Leds85
- Table 3.8 SEL-551 Front-Panel Target LED Definitions85

Section 4: Setting the Relay87

Settings Sheets for the SEL-551 Relay107

Section 5: Serial Port Communications and Commands119

Command Summary146

Section 6: Front-Panel Interface147

Section 7: Standard Event Reports and SER161

Section 8: Testing and Troubleshooting179

Appendix A: Firmware and Manual Versions Firmware198

Table A.2 Instruction Manual Revision History199

Appendix B: Firmware Upgrade Instructions EPROM Firmware Upgrades208

Appendix C: SEL Distributed Port Switch Protocol215

Appendix D: Configuration, Fast Meter, and Fast Operate Commands217

Appendix E: Compressed ASCII Commands225

Appendix F: Setting Negative-Sequence Overcurrent Elements229

Appendix G: Modbus RTU Communications Protocol237

Brand	Sel
Model	551
Category	Relays
Language	English

Sel 551 User Manual

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Sel 551 Specifications

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