Sel 551 User manual

20110408
SEL-551 Relay
Overcurrent Relay
Reclosing Relay
Instruction Manual
*PM551-01-NB*

SEL-551 Relay Instruction Manual Date Code 20110408
The relay contains devices sensitive to Electrostatic Discharge
(ESD). When working on the relay with the front panel removed,
work surfaces and personnel must be properly grounded or
equipment damage may result.
!
CAUTION
This procedure requires that you handle components sensitive
to Electrostatic Discharge (ESD). If your facility is not equipped
to work with these components, we recommend that you
return the relay to SEL for firmware installation.
!
CAUTION
There is danger of explosion if the battery is incorrectly
replaced. Replace only with Ray-O-Vac®no. BR2335 or
equivalent recommended by manufacturer. Dispose of used
batteries according to the manufacturer’s instructions.
!
CAUTION
Verify proper orientation of the new EPROM in the socket
before applying pressure to engage it. Note the orientation
indication provided by the notched inside socket corner and
the notched corner.
!
CAUTION
Do not connect external voltages to the relay contact inputs.
Because the contact inputs are internally wetted, permanent
damage to the relay or external equipment may result from
connecting external voltage to a relay contact input.
!
CAUTION
This device is shipped with default passwords. Default
passwords should be changed to private passwords at
installation. Failure to change each default password to a
private password may allow unauthorized access. SEL shall not
be responsible for any damage resulting from unauthorized
access.
!
WARNING
Operator safety may be impaired if the device is used in a
manner not specified by SEL.
!
WARNING
Contact with instrument terminals can cause electrical shock
that can result in injury or death.
!
DANGER
Contact with this circuitry may cause electrical shock that can
result in injury or death. Removal of enclosure panels exposes
circuitry which may cause electrical shock which can result in
injury or death.
!
DANGER
Le relais contient des pièces sensibles aux décharges
électrostatiques. Quand on travaille sur le relais avec les
panneaux avant ou du dessus enlevés, toutes les surfaces et le
personnel doivent être mis à la terre convenablement pour
éviter les dommages à l’équipement.
!
ATTENTION
Cette procédure requiert que vous manipuliez des composants
sensibles aux décharges électrostatiques (DES). Si vous n'êtes
pas équipés pour travailler avec ce type de composants, nous
vous recommandons de les retourner à SEL pour leur
installation.
!
ATTENTION
Il y a un danger d’explosion si la pile électrique n’est pas
correctement remplacée. Utiliser exclusivement Ray-O-Vac®
No. BR2335 ou un équivalent recommandé par le fabricant. Se
débarrasser des piles usagées suivant les instructions du
fabricant.
!
ATTENTION
Vérifier l’orientation du nouvel EPROM avant d’appliquer la
pression pour l’insérer dans sa base. Noter l’orientation
indiquée par le coin marqué à l’intérieur de la base et le coin
marqué du composant.
!
ATTENTION
Ne pas raccorder de tensions externes sur les bornes des
entrées de contact. Parce que les contacts sont trempés au
mercure, des dommages permanents peuvent résulter pour le
relais ou l’équipement externe à la suite du raccordement
d’une tension externe à une entrée de contact du relais.
!
ATTENTION
Cet appareil est expédié avec des mots de passe par défaut. A
l’installation, les mots de passe par défaut devront être
changés pour des mots de passe confidentiels. Dans le cas
contraire, un accés non-autorisé á l’équipement peut être
possible. SEL décline toute responsabilité pour tout dommage
résultant de cet accés non-autorisé.
!
AVERTISSEMENT
La sécurité de l’opérateur peut être compromise si l’appareil
est utilisé d’une façon non indiquée par SEL.
!
AVERTISSEMENT
Tout contact avec les bornes de l’appareil peut causer un choc
électrique pouvant entraîner des blessures ou la mort.
!
DANGER
Tout contact avec ce circuit peut être la cause d’un choc
électrique pouvant entraîner des blessures ou la mort. Le
retrait des panneaux du boîtier expose le circuit qui peut
causer des chocos électriques pouvant entraîner des blessures
ou la mort.
!
DANGER
© 1998–2011 by Schweitzer Engineering Laboratories, Inc. All rights reserved.
All brand or product names appearing in this document are the trademark or registered trademark of their respective holders. No SEL
trademarks may be used without written permission. SEL products appearing in this document may be covered by US and Foreign patents.
Schweitzer Engineering Laboratories, Inc. reserves all rights and benefits afforded under federal and international copyright and patent laws in
its products, including without limitation software, firmware, and documentation.
The information in this manual is provided for informational use only and is subject to change without notice. Schweitzer Engineering
Laboratories, Inc. has approved only the English language manual.
This product is covered by the standard SEL 10-year warranty. For warranty details, visit www.selinc.com or contact your customer service
representative. PM551-01

Date Code 20110408 Instruction Manual SEL-551 Relay
Table of Contents
List of Tables.......................................................................................................................................................................... v
List of Figures.....................................................................................................................................................................vii
Preface..................................................................................................................................................................................... ix
Manual Overview .............................................................................................................................................. ix
Conventions ........................................................................................................................................................ x
Section 1: Introduction and Specifications
Overview ......................................................................................................................................................... 1.1
SEL-551 Model Changes ................................................................................................................................ 1.2
SEL-551 Applications ..................................................................................................................................... 1.2
Hardware Overview......................................................................................................................................... 1.3
Specifications .................................................................................................................................................. 1.4
Overcurrent Elements...................................................................................................................................... 1.6
CT Saturation Protection ................................................................................................................................. 1.7
Timer Specifications........................................................................................................................................ 1.8
Section 2: Installation
Overview ......................................................................................................................................................... 2.1
Relay Mounting............................................................................................................................................... 2.1
Rear-Panel Connections .................................................................................................................................. 2.5
SEL-551 AC/DC Connection Diagrams for Example Applications ............................................................... 2.9
EIA-485 Rear-Panel Adapter......................................................................................................................... 2.14
Circuit Board Jumpers and Battery ............................................................................................................... 2.15
Section 3: Relay Elements and Logic
Relay Word Bits and SELOGIC Control Equations.......................................................................................... 3.1
Optoisolated Inputs.......................................................................................................................................... 3.3
Local Control Switches ................................................................................................................................... 3.5
Remote Control Switches ................................................................................................................................ 3.7
Instantaneous Overcurrent Elements............................................................................................................... 3.8
Time-Overcurrent Elements .......................................................................................................................... 3.12
Trip Logic ...................................................................................................................................................... 3.17
Close Logic.................................................................................................................................................... 3.20
Reclosing Relay............................................................................................................................................. 3.22
SELOGIC Control Equation Variables/Timers ............................................................................................... 3.38
Output Contacts............................................................................................................................................. 3.39
Demand Ammetering .................................................................................................................................... 3.41
Front-Panel Target LEDs............................................................................................................................... 3.47
Section 4: Setting the Relay
Overview ......................................................................................................................................................... 4.1
Settings Changes Via the Front Panel ............................................................................................................. 4.1
Settings Changes Via the Serial Port ............................................................................................................... 4.1
Time-Overcurrent Element Setting Reference Information ............................................................................ 4.2
Relay Word Bit Setting Reference Information ............................................................................................ 4.14
Settings Explanations .................................................................................................................................... 4.18
Settings Sheets............................................................................................................................................... 4.20
Settings Sheets for the SEL-551 Relay

ii
SEL-551 Relay Instruction Manual Date Code 20110408
Table of Contents
Section 5: Serial Port Communications and Commands
Overview..........................................................................................................................................................5.1
Port Connector and Communications Cables ..................................................................................................5.1
Communications Protocol................................................................................................................................5.4
Serial Port Automatic Messages......................................................................................................................5.7
Serial Port Access Levels.................................................................................................................................5.8
Command Summary ........................................................................................................................................5.9
Command Explanations.................................................................................................................................5.11
SEL-551 Command Summary
Section 6: Front-Panel Interface
Overview..........................................................................................................................................................6.1
Front-Panel Pushbutton Operation...................................................................................................................6.1
Functions Unique to the Front-Panel Interface ................................................................................................6.4
Rotating Default Display ...............................................................................................................................6.11
Section 7: Standard Event Reports and SER
Overview..........................................................................................................................................................7.1
Standard 15-Cycle Event Reports....................................................................................................................7.1
Sequential Events Recorder (SER) Event Report ............................................................................................7.8
Example Standard 15-Cycle Event Report ....................................................................................................7.11
Example Sequential Events Recorder (SER) Event Report...........................................................................7.17
Section 8: Testing and Troubleshooting
Overview..........................................................................................................................................................8.1
Testing Methods and Tools ..............................................................................................................................8.1
Acceptance Testing ..........................................................................................................................................8.4
Commissioning Testing .................................................................................................................................8.14
Maintenance Testing ......................................................................................................................................8.15
Relay Self-Tests .............................................................................................................................................8.16
Relay Troubleshooting...................................................................................................................................8.17
Relay Calibration ...........................................................................................................................................8.18
Factory Assistance .........................................................................................................................................8.18
Appendix A: Firmware and Manual Versions
Firmware .........................................................................................................................................................A.1
Instruction Manual..........................................................................................................................................A.3
Appendix B: Firmware Upgrade Instructions
EPROM Firmware Upgrades.......................................................................................................................... B.1
Flash Firmware Upgrades............................................................................................................................... B.5
Appendix C: SEL Distributed Port Switch Protocol
Overview......................................................................................................................................................... C.1
Settings............................................................................................................................................................ C.1
Operation ........................................................................................................................................................ C.1
Appendix D: Configuration, Fast Meter, and Fast Operate Commands
Overview.........................................................................................................................................................D.1
Message Lists..................................................................................................................................................D.1
Message Definitions........................................................................................................................................D.2

iii
Date Code 20110408 Instruction Manual SEL-551 Relay
Table of Contents
Appendix E: Compressed ASCII Commands
Overview .........................................................................................................................................................E.1
CASCII Command—General Format .............................................................................................................E.1
CASCII Command—SEL-551........................................................................................................................E.3
CSTATUS Command—SEL-551 ....................................................................................................................E.3
CHISTORY Command—SEL-551 .................................................................................................................E.4
CEVENT Command—SEL-551 .....................................................................................................................E.4
Appendix F: Setting Negative-Sequence Overcurrent Elements
Setting Negative-Sequence Definite-Time Overcurrent Elements .................................................................. F.1
Setting Negative-Sequence Time-Overcurrent Elements ................................................................................ F.1
Coordinating Negative-Sequence Overcurrent Elements................................................................................ F.2
Other Negative-Sequence Overcurrent Element References........................................................................... F.7
Appendix G: Modbus RTU Communications Protocol
Overview ........................................................................................................................................................ G.1
Modbus RTU Communications Protocol ....................................................................................................... G.1

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Date Code 20110408 Instruction Manual SEL-551 Relay
List of Tables
Table 1.1 Overcurrent Elements............................................................................................................. 1.6
Table 2.1 Required Control Voltage Jumper Positions for Applied Nominal Control Voltage
(SEL-551 With the Conventional Terminal Blocks Option) ............................................ 2.15
Table 2.2 Required Position of Jumper JMP13 for Desired Output Contact OUT4 Operation........... 2.17
Table 3.1 Processing Order of SELOGIC Control Equation Operators................................................... 3.1
Table 3.2 Processing Order of Relay Elements and Logic (Top to Bottom).......................................... 3.3
Table 3.3 Correspondence Between Local Control Switch Positions and Label Settings..................... 3.5
Table 3.4 Correspondence Between Local Control Switch Types and Required Label Settings........... 3.6
Table 3.5 Relay Word Bit and Front-Panel Correspondence to Reclosing Relay States ..................... 3.23
Table 3.6 Shot Counter Correspondence to Relay Word Bits and Open Interval Times ..................... 3.27
Table 3.7 Demand Ammeter Settings and Settings Range .................................................................. 3.43
Table 3.8 SEL-551 Front-Panel Target LED Definitions..................................................................... 3.47
Table 4.1 Serial Port SET Commands.................................................................................................... 4.1
Table 4.2 SET Command Editing Keystrokes........................................................................................ 4.2
Table 4.3 Equations Associated With U.S. Curves ................................................................................ 4.3
Table 4.4 Equations Associated With IEC Curves................................................................................. 4.3
Table 4.5 SEL-551 Relay Word Bits.................................................................................................... 4.14
Table 4.6 Relay Word Bit Definitions.................................................................................................. 4.14
Table 5.1 Serial Communications Port Pin Function Definitions .......................................................... 5.4
Table 5.2 Communications Settings....................................................................................................... 5.6
Table 5.3 Serial Port Automatic Messages ............................................................................................ 5.7
Table 5.4 Serial Port Command Summary........................................................................................... 5.10
Table 5.5 ACC and 2AC Commands ................................................................................................... 5.11
Table 5.6 SEL-551 Relay Word and Its Correspondence to TAR Command
and Front-Panel LEDs ...................................................................................................... 5.21
Table 5.7 SEL-551 Control Subcommands.......................................................................................... 5.23
Table 5.8 Valid Password Characters ................................................................................................... 5.24
Table 7.1 Event Types ............................................................................................................................ 7.4
Table 7.2 Standard Event Report Current Columns............................................................................... 7.5
Table 7.3 Other Standard Event Report Columns.................................................................................. 7.6
Table 7.4 SEL-551 Input/Output Event Report Columns ...................................................................... 7.8
Table 7.5 SER Report Row Commands and Format.............................................................................. 7.9
Table 8.1 Instantaneous Overcurrent Elements and Corresponding Settings/Relay
Word Bits/TAR Commands .............................................................................................. 8.10
Table 8.2 Inverse-Time Overcurrent Elements and Corresponding Settings/Relay
Word Bits/TAR Commands .............................................................................................. 8.12
Table 8.3 Relay Self Tests.................................................................................................................... 8.16
Table 8.4 Troubleshooting Procedures................................................................................................. 8.17
Table A.1 Firmware Revision History ................................................................................................... A.1
Table A.2 Instruction Manual Revision History .................................................................................... A.3
Table D.1 Binary Message List.............................................................................................................. D.1
Table D.2 ASCII Configuration Message List....................................................................................... D.2
Table D.3 A5C0 Relay Definition Block ............................................................................................... D.2
Table D.4 A5C1 Fast Meter Configuration Block ................................................................................. D.2
Table D.5 A5D1 Fast Meter Data Block................................................................................................ D.4
Table D.6 A5C2/A5C3 Demand/Peak Demand Fast Meter Configuration Messages........................... D.4
Table D.7 A5D2/A5D3 Demand/Peak Demand Fast Meter Message ................................................... D.5
Table D.8 A5CE Fast Operate Configuration Block.............................................................................. D.6
Table D.9 A5E0 Fast Operate Remote Bit Control................................................................................ D.7
Table D.10 A5E3 Fast Operate Breaker Control ..................................................................................... D.7
Table G.1 Modbus Query Fields ............................................................................................................ G.1
Table G.2 SEL-551 Modbus Function Codes ........................................................................................ G.2
Table G.3 SEL-551 Modbus Exception Codes ...................................................................................... G.2
Table G.4 01h Read Coil Status Commands.......................................................................................... G.3

vi List of Tables
SEL-551 Relay Instruction Manual Date Code 20110408
Table G.5 02h Read Input Status Command ..........................................................................................G.4
Table G.6 03h Read Holding Register Command..................................................................................G.5
Table G.7 04h Read Holding Register Command..................................................................................G.5
Table G.8 05h Force Single Coil Command ..........................................................................................G.6
Table G.9 SEL-551 Command Coils......................................................................................................G.6
Table G.10 06h Preset Single Register Command ...................................................................................G.7
Table G.11 07h Read Exception Status Command ..................................................................................G.7
Table G.12 08h Loopback Diagnostic Command ....................................................................................G.8
Table G.13 10h Preset Multiple Registers Command ..............................................................................G.9
Table G.14 64h Scattered Register Read Command ..............................................................................G.10
Table G.15 SEL-551 Modbus Command Region...................................................................................G.11
Table G.16 Modbus Command Codes....................................................................................................G.11
Table G.17 Assign Event Report Channel Using Address 00B2 ........................................................... G.13
Table G.18 Modbus Map........................................................................................................................G.13

Date Code 20110408 Instruction Manual SEL-551 Relay
List of Figures
Figure 1.1 SEL-551 Relays Applied Throughout the Power System...................................................... 1.2
Figure 1.2 SEL-551 Inputs, Outputs, and Communications Port............................................................ 1.3
Figure 1.4 SEL-551 Instantaneous Overcurrent Element Pickup Time Curve........................................ 1.7
Figure 1.5 SEL-551 Relay Instantaneous Overcurrent Element Reset Time Curve................................ 1.7
Figure 2.1 SEL-551 Dimensions, Panel Cutout, and Drill Plan .............................................................. 2.2
Figure 2.2 Relay Dimensions and Drill Plan for Mounting Two SEL-500 Series Relays Together
Using Mounting Block (SEL P/N 9101) ............................................................................ 2.3
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)...................................................................... 2.4
Figure 2.4 SEL-551 Fitted with Mounting Bracket (SEL P/N 9100) for Mounting
in 19-Inch Rack .................................................................................................................. 2.4
Figure 2.5 SEL-551 Front Panel, Rack-Mount Version (Half-Rack Width)........................................... 2.5
Figure 2.6 SEL-551 Front Panel, Panel-Mount Version ......................................................................... 2.5
Figure 2.7 SEL-551 Rear Panel (Conventional Terminal Blocks Option) .............................................. 2.6
Figure 2.8 SEL-551 Rear Panel (Plug-In Connectors Option) ................................................................ 2.7
Figure 2.9 SEL-551 Provides Overcurrent Protection and Reclosing for a Utility Distribution
Feeder (Includes Fast Bus Trip Scheme)............................................................................ 2.9
Figure 2.10 SEL-551 Provides Overcurrent Protection for an Industrial Distribution Feeder
(Core-Balance Current Transformer Connected to Current Input Channel IN)............... 2.10
Figure 2.11 SEL-551 Provides Overcurrent Protection for a Delta-Wye Transformer Bank ................. 2.11
Figure 2.12 SEL-551 Provides Overcurrent Protection for a Transformer Bank with a Tertiary
Winding ............................................................................................................................ 2.12
Figure 2.13 SEL-551 Provides Overcurrent Protection for a Distribution Bus (Includes Fast Bus
Trip Scheme) ....................................................................................................................2.13
Figure 2.14 SEL-551 Provides Dedicated Breaker Failure Protection.................................................... 2.14
Figure 2.15 Input and Output Jumper Locations (SEL-551 Relay With the Conventional Terminal
Blocks With Jumper-Selectable Control Input Voltage Option)...................................... 2.16
Figure 2.16 Output Contact OUT4 Control Jumper Location................................................................. 2.17
Figure 3.1 Example Operation of SEL-551 Optoisolated Inputs ............................................................ 3.3
Figure 3.2 Local Control Switches Drive Local Bits LB1–LB8 ............................................................. 3.5
Figure 3.3 Remote Control Switches Drive Remote Bits RB1–RB8 ...................................................... 3.8
Figure 3.4 Phase Instantaneous Overcurrent Elements 50P1–50P6........................................................ 3.9
Figure 3.5 Single-Phase Instantaneous Overcurrent Elements 50A, 50B, and 50C.............................. 3.10
Figure 3.6 Neutral Ground Instantaneous Overcurrent Elements 50N1 and 50N2............................... 3.10
Figure 3.7 Residual Ground Instantaneous Overcurrent Elements 50G1 and 50G2............................. 3.11
Figure 3.8 Negative-Sequence Instantaneous Overcurrent Elements 50Q1 and 50Q2 ......................... 3.11
Figure 3.9 Phase Time-Overcurrent Elements 51P1T and 51P2T......................................................... 3.12
Figure 3.10 Neutral Ground Time-Overcurrent Element 51N1T ............................................................ 3.15
Figure 3.11 Residual Ground Time-Overcurrent Element 51G1T .......................................................... 3.15
Figure 3.12 Negative-Sequence Time-Overcurrent Elements 51Q1T and 51Q2T.................................. 3.16
Figure 3.13 Trip Logic............................................................................................................................. 3.17
Figure 3.14 Close Logic .......................................................................................................................... 3.20
Figure 3.15 Reclosing Relay States and General Operation.................................................................... 3.22
Figure 3.16 Reclosing Sequence From Reset to Lockout With Factory Settings ................................... 3.25
Figure 3.17 Voltage Relay (27/59) Provides Reclose Block Signal to SEL-551 .................................... 3.32
Figure 3.18 Sequence Coordination Between the SEL-551 and a Line Recloser ................................... 3.35
Figure 3.19 Operation of SEL-551 Shot Counter for Sequence Coordination With Line Recloser
(Additional Settings Example 1) ...................................................................................... 3.35
Figure 3.20 Operation of SEL-351 Relay Shot Counter for Sequence Coordination With Line
Recloser (Additional Setting Example 2)......................................................................... 3.37
Figure 3.21 SELOGIC Control Equation Variables/Timers ...................................................................... 3.38
Figure 3.22 Dedicated Breaker Failure Scheme Created With SELOGIC Variables/Timers.................... 3.39
Figure 3.23 Logic Flow for Example SEL-551 Output Contact Operation............................................. 3.40
Figure 3.24 Response of Thermal Demand Ammeter to a Step Input
(Setting DMTC = 15 minutes).......................................................................................... 3.42
Figure 3.25 Voltage VSApplied to Series RC Circuit............................................................................. 3.43
Figure 3.26 Demand Current Logic Outputs ........................................................................................... 3.44
Figure 3.27 Raise Pickup of Residual Ground Time-Overcurrent Element for Unbalance Current ....... 3.45

viii List of Figures
SEL-551 Relay Instruction Manual Date Code 20110408
Figure 4.1 U.S. Moderately Inverse Curve: U1 .......................................................................................4.4
Figure 4.2 U.S. Inverse Curve: U2...........................................................................................................4.5
Figure 4.3 U.S. Very Inverse Curve: U3..................................................................................................4.6
Figure 4.4 U.S. Extremely Inverse Curve: U4.........................................................................................4.7
Figure 4.5 U.S. Short-Time Inverse Curve: U5 .......................................................................................4.8
Figure 4.6 IEC Class A Curve (Standard Inverse): C1............................................................................4.9
Figure 4.7 IEC Class B Curve (Very Inverse): C2 ................................................................................4.10
Figure 4.8 IEC Class C Curve (Extremely Inverse): C3........................................................................4.11
Figure 4.9 IEC Long-Time Inverse Curve: C4 ......................................................................................4.12
Figure 4.10 IEC Short-Time Inverse Curve: C5 ......................................................................................4.13
Figure 5.1 Nine-Pin Serial Communications Port Connector..................................................................5.1
Figure 6.1 SEL-551 Front-Panel Pushbuttons—Overview ......................................................................6.1
Figure 6.2 SEL-551 Front-Panel Pushbuttons—Primary Functions........................................................6.2
Figure 6.3 SEL-551 Front-Panel Pushbuttons-Primary Functions (continued) .......................................6.3
Figure 6.4 SEL-551 Front-Panel Pushbuttons-Secondary Functions.......................................................6.4
Figure 6.5 Local Control Switch Configured as an ON/OFF Switch ......................................................6.7
Figure 6.6 Local Control Switch Configured as an OFF/MOMENTARY Switch ..................................6.7
Figure 6.7 Local Control Switch Configured as an ON/OFF/MOMENTARY Switch............................6.7
Figure 7.1 Example Event Summary .......................................................................................................7.3
Figure 7.2 Example SEL-551 Standard 15-Cycle Event Report (1/8-Cycle Resolution)......................7.14
Figure 7.3 Derivation of Event Report Current Values and RMS Current Values From Sampled
Current Waveform ............................................................................................................7.15
Figure 7.4 Derivation of Phasor RMS Current Values From Event Report Current Values ..................7.16
Figure 7.5 Example Sequential Events Recorder (SER) Event Report .................................................7.17
Figure 8.1 Low-Level Test Interface ........................................................................................................8.2
Figure 8.2 Relay Part Number and Hardware Identification Sticker .......................................................8.5
Figure 8.3 Test Connections for Balanced Load With Three-Phase Current Sources .............................8.9
Figure 8.4 Test Connections for Balanced Load With Two-Phase Current Sources................................8.9
Figure B.1 EPROM Socket...................................................................................................................... B.2
Figure B.2 Insertion of the Extraction Tool in the EPROM Socket ........................................................ B.3
Figure B.3 Proper Orientation of the EPROM and EPROM Socket ....................................................... B.3
Figure F.1 Minimum Response Time Added to a Negative-Sequence Time-Overcurrent Element ........F.2
Figure F.2 Distribution Feeder Protective Devices .................................................................................. F.3
Figure F.3 Traditional Phase Coordination ..............................................................................................F.4
Figure F.4 Phase-to-Phase Fault Coordination.........................................................................................F.5
Figure F.5 Negative-Sequence Overcurrent Element Derived From “Equivalent” Phase
Overcurrent Element, 51EP ................................................................................................F.6