What does the SEL RTAC do?

The RTAC collects data from relays via SEL protocol, DNP3, Modbus, and IEC 61850, concentrates it into a unified tag database, presents it to SCADA via DNP3 or ICCP, runs IEC 61131-3 automation logic, and serves a web-based HMI.

Is the SEL RTAC a PLC?

Not a conventional PLC — it is purpose-built for power systems with native protection protocol support, pre-built power system function blocks, and multi-protocol gateway capability alongside IEC 61131-3 programmability.

What is the difference between SEL-3530 and SEL-3555?

SEL-3530 is the established RTAC. SEL-3555 is the next-generation with enhanced cybersecurity (secure boot, TPM, updated cryptography) — preferred for new NERC CIP deployments.

Complete Guide to the SEL Real Time Automation Controller (RTAC)

Quick Answer

The SEL Real Time Automation Controller (RTAC) is a substation automation controller and multi-protocol gateway manufactured by Schweitzer Engineering Laboratories. It collects data from SEL and third-party relays using SEL protocol, DNP3, Modbus, and IEC 61850, and presents aggregated data to utility SCADA masters via DNP3 or ICCP. The RTAC also runs IEC 61131-3 control logic for substation automation applications and provides an embedded web-based HMI for operator displays.

What Is the SEL RTAC?

The RTAC serves four roles in substation automation: protocol gateway (translating between SEL protocol, DNP3, Modbus, IEC 61850, and ICCP), data concentrator (aggregating multiple relay data to a single SCADA point), automation controller (executing IEC 61131-3 logic), and substation HMI (serving web-based operator displays). See What Is the SEL RTAC? for details.

RTAC Hardware Platforms

SEL-3530 — Established rack-mount RTAC with broad protocol support
SEL-3354 — Ruggedized Linux computer running RTAC software for high-processing applications
SEL-3555 — Next-generation RTAC with enhanced cybersecurity (secure boot, TPM, improved cryptography)

ACSELERATOR RTAC Software (SEL-5033)

ACSELERATOR RTAC is the integrated development environment for configuring tag databases, protocol drivers, IEC 61131-3 programs, and HMI pages. See the interface overview for navigation details.

RTAC as Protocol Gateway

The RTAC simultaneously runs multiple protocol clients and servers:

SEL Protocol Client — Polls SEL relays for relay word bits, metering, and events
DNP3 Master — Polls third-party RTUs (SCADAPack, Bristol FB300, ABB Totalflow)
DNP3 Outstation — Serves aggregated data to Geo SCADA and Ignition
Modbus Client/Server — Polls meters and drives, serves data to legacy SCADA
IEC 61850 Client — Reads MMS data and subscribes to GOOSE from modern IEDs

RTAC as IEC 61131-3 Automation Controller

The RTAC runs IEC 61131-3 programs in Ladder Diagram, Structured Text, Function Block Diagram, and Sequential Function Chart. SEL provides a power system function block library with pre-built protection and automation logic.

RTAC Tag Database

The tag database is the central data hub — all protocol drivers read and write tags, all programs access tags, and all HMI elements bind to tags.

RTAC HMI and Operator Displays

The RTAC includes an embedded web server for operator display pages — one-line diagrams, metering, alarm lists, and trends accessible from any browser on the substation LAN.

Cybersecurity and NERC CIP

RTAC cybersecurity hardening covers password management, port hardening, audit logging, DNP3 Secure Authentication, and NERC CIP compliance for BES cyber systems.