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      Real-Time Automation Controller (RTAC)

      The SEL-3555 is our most powerful RTAC model, featuring multicore processing and configurable RAM options capable of running multiple applications simultaneously and meeting the industry's most demanding requirements. The optional integrated web HMI with a local display port eliminates the need for an additional computer. Ideal for the most demanding applications, this model integrates up to 256 devices and supports up to 100,000 data points.

      For more information about the RTAC automation platform, its applications, and other available models, visit the RTAC platform page.

      Starting At


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      Rugged Hardware—The RTAC is designed and tested to meet or exceed IEEE 1613 and protective relay specifications for harsh environments and to withstand vibration, electrical surges, fast transients, and extreme temperatures. The SEL RTAC operates reliably, even in challenging environments. For added protection, you can order conformal coating to protect against harsh environments and airborne contaminants, such as hydrogen sulfide, chlorine, salt, and moisture. Learn more about conformal coating.

      Simple, Seamless Configuration—Quickly design an integrated automation system that includes protocol conversion, SCADA communications, IEC 61850 integration, synchrophasors, time synchronization, data management, and programmable logic. New automation tools are continuously being added to simplify complex applications, such as condition monitoring, disturbance fault recording, configuring SCADA point maps, and archiving and alarming for data changes. See the acSELerator RTAC SEL-5033 Software manual for more information on our automation software extensions.

      Extensive Protocol Support—Concentrate and manage data from new and legacy relays and other IEDs using our extensive set of protocols. Standard SCADA protocols are included with the purchase of any RTAC, including DNP3, IEC 60870-101/104, Modbus, and many more.  

      Integrated Security—The RTAC is built with cybersecurity from the hardware up. Exe-GUARD approvelist anti-malware technology provides increased security, making the RTAC the first product in the market to include an approvelist antivirus solution that does not require end-user patch updates. Make the RTAC the secure access point into your substation or plant with a full-featured set of engineering access tools. Authenticate using LDAP or RADIUS central authentication or local role-based user authentication. Restrict users access to the required set of functions to do the job with configurable role-based access control (RBAC). Log user activity in the Sequence of Events (SOE) log, and forward notifications via Syslog. Encrypt critical data and engineering access via Secure Shell (SSH) and Transport Layer Security (TLS). The RTAC enforces authentication and proxies engineering access connections for serial and LAN-connected devices.

      Custom Logic—Create your logic solutions in the embedded IEC 61131 logic engine, which comes standard with every automation controller. Build custom user logic and access all system tags, including diagnostics, contact I/O, protocol data, and communications statistics, to provide unparalleled control flexibility.

      Substation HMI—Provide cost-effective local and remote monitoring, control, and annunciation for substations and other processes by installing the optional web-based HMI, available for most RTAC models and the SEL-2240 Axion. acSELerator Diagram Builder SEL-5035 Software easily maps the RTAC tag database to reduce screen development time.


        1. 1

          Lamp test button

        2. 2

          Ethernet activity LEDs

        3. 3

          Serial port activity LEDs

        4. 4

          SSD activity LED

        5. 5

          Programmable bicolor LEDs

        6. 6

          2 front-panel USB 3.1 ports

        7. 7

          SSD with storage capacity up to 480 GB

        1. 1

          DVI-D ports

        2. 2

          2 high-speed Gigabit Ethernet ports

        3. 3

          4 USB 3.1 ports

        4. 4

          2 built-in EIA-232 ports

        5. 5


        6. 6

          Form C alarm contact output

        7. 7

          PCIe expansion slots

        8. 8

          6 EIA-232/422/485 ports

        9. 9

          Dual hot-swappable power supplies



      The SEL RTAC is a powerful, multifunctional platform designed for the most demanding utility and industrial applications. With precise, deterministic processing, integrated cybersecurity features, and rugged, industrial-grade hardware, the RTAC ensures reliable performance for critical operations, even in the harshest operating environments.

      The RTAC platform offers a range of hardware options, extensive protocol support, and an embedded IEC 61131 logic engine for custom programming—making it a versatile solution for a variety of applications, ranging from data concentration and protocol conversion to comprehensive power management and control.

      For more information about the RTAC automation platform, its applications, and other available models, visit the RTAC platform page.

      Minimum Software Version

      Video Playlists

      Videos in this series:

      • SEL RTAC—Install
      • SEL RTAC—Basic Software
      • SEL RTAC—Building a Project
      • SEL RTAC—DNP Client
      • SEL RTAC—Tag Processor Intro
      • SEL RTAC—Tag Processor Logging
      • SEL RTAC—Tag Processor Logic
      • SEL RTAC—Engineering Access with Legacy Commands
      • SEL RTAC—Engineering Access with Automatic Connections
      • SEL RTAC—IEC 61131 Programming
      • SEL RTAC—IEC 61131 Functions
      • SEL RTAC—IEC 61131 Function Blocks

      Videos in this series:

      • How to Use the RTAC HMI, Part 1: acSELerator Diagram Builder Overview
      • How to Use the RTAC HMI, Part 2: Building a Project
      • How to Use the RTAC HMI, Part 3: Shared Tags

      Latest Firmware Versions

      There are no firmware versions available for this product.

      Product Revision Firmware ID Date Available Serial Number
      SEL-3555 R151-V2 SEL-3555-R151-V2-Z000102-D20230314 3/21/23 ~1220800001
      SEL-3555 R150-V4 SEL-3350-R150-V4-Z000164-D20230313 3/21/23 ~1220800001
      SEL-3555 R149-V6 SEL-3555-R149-V6-Z000101-D20230313 3/21/23 ~1220800001
      SEL-3555 R148-V9 SEL-3555-R148-V9-Z000093-D20230313 3/21/23 ~1220800001

      The Firmware IDs for older versions of the firmware can typically be found in Appendix A of the instruction manual.

      Minimum Software Version

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      Sales Resource Central

      RTAC Software Tab

      Configuration Software

      acSELerator RTAC SEL-5033 Software

      acSELerator RTAC is an intuitive, easy-to-use Microsoft Windows application designed to configure the RTAC family of products, including the SEL 2240 Axion®.

      Learn more and download on the SEL-5033 software page.

      acSELerator Diagram Builder SEL-5035 Software

      acSELerator Diagram Builder is a Microsoft Windows application that allows users to create and manage visualization projects for the optional web-based human-machine interface (HMI) designed for the RTAC platform.

      Learn more and download on the SEL-5035 software page.

      Additional Software Options

      A wide range of software tools, add-ons, and library extensions are available for the RTAC platform. Instructions for extension libraries are available in the Programming Reference and via the acSELerator RTAC help menu once libraries are downloaded.

      Automation Solutions

      The following software options can be added during RTAC hardware configuration.

      HMI1Visualize data and create custom diagrams for real-time monitoring and control.None
      Network Audit Utilities2Scan local area networks (LAN) and provide an audit of devices and communications on the network.None
      Grid ConnectControl the point of common coupling (PCC) between the utility and renewable power generation sources.Dynamic Disturbance Recorder, File I/O
      Horizon SVP PlusTurn the RTAC into a synchrophasor vector processor. Detect the onset of uncontrolled wide-area oscillations with SVPplus modal analysis.None
      Horizon Power System ModelResolve synchrophasor data streams using a model of the power system.File I/O
      Condition MonitoringImplement condition-based monitoring of power system assets to assist with NERC PRC-005 compliance.File I/O
      Dynamic Disturbance RecorderCollect data from within the logic engine to generate Sequence of Events (SOE), time-aligned CSV, and COMTRADE files in the RTAC.File I/O
      Meter Report Trend RecorderRecord analog data in the RTAC, and send data to acSELerator Team SEL-5045 and acSELerator Meter Reports SEL-5630 Software for analysis.File I/O
      Report Generator/Email ClientGenerate custom reports from data available from the RTAC's logic engine. It is bundled with a fully featured email client that integrates into secure email systems.File I/O
      FTP SyncConnect to established S/FTP server infrastructure and automatically push files from the RTAC file system to remote destinations.File I/O
      File I/ORead and write files to the RTAC file system. It includes a built-in SFTP/FTP client for sending and receiving files and provides programmatic access to fault and SOE records.None

      1Not supported on the SEL-3505 and SEL-3505-3
      2Only supported on the SEL-3350, SEL-3555, SEL-3560S, and SEL-3560E

      Engineering Services Solutions

      Contact Engineering Services for ordering information and additional details about these software options.

      Distribution AutomationFault location, isolation, restoration, and volt-VAR control of distribution feeders
      Ground Fault DetectionGround fault identification for ungrounded power systems
      Falling Conductor MitigationUse synchrophasors to detect and mitigate broken and falling conductor scenarios

      RTAC Supported Protocols Tab

      • Client Protocols
        • CDC Type II
        • Courier
        • CP 2179
        • DNP3 Serial, DNP3 LAN/WAN
        • eDNA1
        • EtherNet/IP—Explicit Message Client*
        • File Transfer Protocol (FTP)/Secure FTP (SFTP)*
        • Flex Parse
        • IEC 60870-5-101/104
        • IEC 60870-5-103
        • IEC 61850 MMS and MMS Client File Services*,2
        • IEEE C37.118 Synchrophasors
        • LG 8979
        • Modbus RTU, Modbus TCP
        • SEL Protocols
        • SES-92
        • Simple Network Management Protocol (SNMP)
      • Server Protocols
        • CDC Type II
        • DNP3 Serial, DNP3 LAN/WAN
        • EtherNet/IP—Implicit Message Adapter*
        • FTP/SFTP
        • IEC 60870-5-101/104
        • IEC 61850 MMS and MMS Server File Services*
        • IEEE C37.118 Synchrophasors
        • LG 8979
        • Modbus RTU, Modbus TCP
        • SEL Protocols
        • SES-92
        • SNMP Agent
      • Peer-to-Peer Protocols
        • IEC 61850 GOOSE*
        • Network Global Variable List (NGVL)
        • SEL Mirrored Bits Communications
      • Field Bus Protocol
        • EtherCAT to SEL-2240 Axion I/O Modules*,2

      *Optional feature
      1Only supported on the SEL-3555, SEL-3560S, and SEL-3560E
      2Not supported on the SEL-3505 and SEL-3505-3

      Product Certifications