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Provides an overview of the manual's sections, detailing the content and purpose of each chapter.
Explains typographic conventions, hazard statements, and formatting attributes used throughout the manual for clarity.
Introduces the SEL-551 relay, its key features, applications in power systems, and differences from the SEL-551C model.
Details the physical components and connection interfaces of the SEL-551 relay, including rear-panel options and ports.
Lists comprehensive technical specifications covering electrical characteristics, environmental tests, and safety certifications of the SEL-551 relay.
Describes the instantaneous and time-overcurrent elements available, their types, and setting ranges.
Explains the relay's mechanism for handling Current Transformer saturation during heavy fault conditions for phase overcurrent elements.
Details the specifications and accuracy of the timers used for reclosing, programmable functions, and other timing operations.
Guides the user through the installation process, covering relay mounting, wiring, and configuration for optimal application.
Provides instructions and dimensional drawings for both rack mount and panel mount installation of the SEL-551 relay.
Details the wiring options for the rear-panel, including conventional terminal blocks and plug-in connectors.
Explains the function of internal jumpers for configuring control voltage and output contacts, and procedures for battery replacement.
Explains relay word bits and how they are used in SELOGIC control equations to create custom logic and protection schemes.
Describes the operation and application of optoisolated inputs (IN1, IN2) and their use in SELOGIC control equations for status monitoring.
Details the functionality of local control switches for enabling/disabling schemes and operating breaker functions directly from the front panel.
Covers the various instantaneous overcurrent elements (phase, single-phase, ground, negative-sequence) and their operating principles.
Explains the different types of time-overcurrent elements (phase, ground, negative-sequence) and their coordination with timers.
Describes the flexible tripping logic mechanisms controlled by SELOGIC equations, including trip conditions and unlatch logic.
Details the logic governing circuit breaker closing and automatic reclosing operations, including conditions and sequence control.
Explains the states, operation, and settings of the reclosing relay, including shot counters, interval timers, and lockout conditions.
Introduces SELOGIC variables (SV1-SV14) and their use as timers for implementing complex control logic and protection functions.
Explains how output contacts (OUT1-OUT4, ALARM) are controlled by SELOGIC equations and serial port commands for various functions.
Covers the relay's demand and peak demand ammetering capabilities, including settings, operation, and logic applications.
Defines the function and meaning of each front-panel target LED, indicating relay status, fault types, and element operation.
Outlines the methods for changing and viewing relay settings via serial port commands and the front panel.
Guides users on how to access and modify relay settings directly using the front-panel pushbuttons.
Explains the procedure for changing relay settings remotely using serial port commands like SET n s.
Provides detailed tables and graphs for setting time-overcurrent elements, including U.S. and IEC inverse time curves.
Lists and defines all available relay word bits, explaining their function and primary application in SELOGIC equations.
Clarifies settings that lack explicit references elsewhere, covering identifier labels, CT sizing criteria, and other system parameters.
Introduces the serial port capabilities of the SEL-551, including connection options and default communication parameters.
Details the physical serial port connector and provides pinout information for EIA-232 and EIA-485 options, along with cable diagrams.
Explains the hardware (RTS/CTS) and software protocols (SEL ASCII, LMD, Fast Meter, Modbus RTU) used for serial communications.
Describes the SEL ASCII protocol for communication, including command format, message structure, and flow control mechanisms.
Details the Modbus RTU protocol, its master/slave operation, supported function codes, and exception responses.
Explains the hierarchical access levels (0, 1, 2, C) for serial port commands, including password management.
Provides a comprehensive summary of all serial port commands, their access levels, descriptions, and front-panel pushbutton equivalents.
Introduces the front-panel interface, detailing how to access information, configure settings, and control operations.
Explains the primary and secondary functions of front-panel pushbuttons and their mapping to serial port commands.
Guides users on setting and managing front-panel passwords for accessing different command levels, including default passwords.
Describes the navigation and editing procedures for secondary functions, such as selecting settings and changing digits using arrow buttons.
Highlights specific functions accessible only via the front panel, such as the reclosing relay shot counter and local control operations.
Explains how to use the front panel for local control of schemes, breaker operations, and emulating switch types via local bits.
Describes how the front-panel display shows the relay name, local control status, and enabled display point labels in a rotating sequence.
Introduces the two event reporting mechanisms: standard 15-cycle event reports and Sequential Events Recorder (SER) reports.
Details the triggering conditions, storage, and display of standard 15-cycle event reports, including event summaries.
Explains the data fields included in event summaries, such as event type, shot count, and current magnitudes.
Describes how to retrieve stored 15-cycle event reports using serial port commands like EVENT n, C, L, and R.
Explains the SER report, triggered by programmable conditions, listing state changes with time stamps and storing up to 512 rows.
Details how to configure SER trigger lists (SER1, SER2, SER3) by selecting up to 24 relay word bits for event triggering.
Explains how to access stored SER event report rows using the SER command with row numbers or date ranges.
Introduces the different types of relay testing (acceptance, commissioning, maintenance) and troubleshooting methodologies.
Lists features assisting in relay testing, including METER, EVENT, TARGET commands, and programmable outputs for isolated testing.
Describes the low-level test interface for connecting test equipment, allowing AC current or voltage signal injection for testing.
Covers the goals, test items, and required equipment for verifying relay performance and application suitability.
Details the objectives and checks for commissioning a new protection system, ensuring correct connections and settings.
Explains the approach to maintenance testing, emphasizing periodic verification and analysis of reporting functions.
Describes the relay's built-in self-tests, corrective actions for failures, and how to view status reports.
Provides inspection procedures and troubleshooting steps for common relay issues, including LED status and communication problems.
Explains how to find the firmware version and lists the revision history of firmware releases for the SEL-551 relay.
Provides a revision history of the instruction manual, detailing modifications made to different sections across various versions.
Introduces the two firmware types (EPROM, Flash) and outlines the general process for upgrading firmware.
Provides detailed, step-by-step instructions for physically replacing an EPROM component on the relay's main board for firmware upgrades.
Details the procedure for upgrading Flash firmware via a PC and terminal emulation software using serial port communication.
Introduces the SEL Distributed Port Switch Protocol (LMD) for sharing a communications channel among multiple SEL relays.
Explains the settings required to enable and configure the LMD protocol, including PROTOCOL, PREFIX, ADDRESS, and SETTLE TIME.
Describes the operational steps for using the LMD protocol, including initial message detection and command execution.
Introduces the data streams for ASCII commands and binary data, supporting fast metering and operate functions.
Lists the available binary (A5xx) and ASCII configuration messages for accessing relay data and configuration.
Provides detailed definitions and formats for various binary messages related to configuration, fast meter, and fast operate commands.
Introduces Compressed ASCII commands for efficient data retrieval in spreadsheet or database formats.
Explains the general structure and syntax of Compressed ASCII commands, including message formatting and checksum calculation.
Provides the specific Compressed ASCII configuration message output by the SEL-551 upon receiving the CAS command.
Details the format of status data provided by the SEL-551 in Compressed ASCII when the CST command is issued.
Describes how to retrieve historical data in Compressed ASCII format using the CHI command.
Explains the CEV command for displaying event reports in Compressed ASCII, including optional parameters for report selection.
Advises on avoiding direct tripping for negative-sequence elements, recommending timers for definite-time operation to prevent nuisance tripping.
Recommends using timers for negative-sequence time-overcurrent elements with low time-dial settings to mitigate transient current issues.
Provides guidelines and an example for coordinating negative-sequence overcurrent elements with downstream phase overcurrent devices for proper protection selectivity.
Outlines a step-by-step process for coordinating negative-sequence overcurrent elements, starting from the furthest downstream protective device.
Presents a generic coordination scenario involving feeder and line recloser relays, illustrating the application of negative-sequence coordination principles.
Explains how to derive an "equivalent" phase overcurrent element for coordination purposes by applying specific guidelines.
Details the calculation method for converting equivalent phase overcurrent settings to negative-sequence settings using a specified equation.
Discusses the benefits of using negative-sequence elements for distribution bus protection, enhancing phase-to-phase fault sensitivity.
Lists technical papers providing further insights into negative-sequence overcurrent element applications and coordination strategies.
Introduces the Modbus RTU protocol for SEL-551 communication, highlighting master/slave architecture and supported features.
Explains the fundamentals of Modbus RTU, including half-duplex communication and the request-response mechanism.
Describes the structure of Modbus queries, detailing fields like Slave Address, Function Code, Data Region, and CRC.
Lists the Modbus function codes supported by the SEL-551 and provides brief descriptions for each.
Details the Modbus exception codes that the SEL-551 returns for various error conditions, aiding in error handling.
Explains how to use Modbus function codes 06h and 10h to control SEL-551 output contacts by writing command codes to registers.
Explains how to control remote bits (RB1–RB8) using Modbus command code 0Ch, including set, clear, and pulse operations.
Provides instructions for downloading event data from the SEL-551 via Modbus, specifying register addresses for event number, channel, and data.
States that Access Level 0 is limited to entering Access Level 1, with specific prompts and password handling if the jumper is absent.
Lists commands for viewing information like settings and metering, detailing prompts and descriptions for each command.
Lists commands for changing settings, operating parameters, and output contacts, including prompts and detailed descriptions.
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