What Is the SEL RTAC? Introduction to the Real Time Automation Controller
Key Takeaway
The SEL RTAC is a substation automation controller serving four roles: protocol gateway, data concentrator, IEC 61131-3 automation controller, and embedded HMI server.
Quick Answer
The SEL RTAC is a substation automation controller that serves four roles: protocol gateway (translating between SEL protocol, DNP3, Modbus, IEC 61850, ICCP), data concentrator (aggregating multiple relay data to one SCADA point), IEC 61131-3 automation controller, and embedded web-based HMI server.
Why RTAC Exists
- Legacy relays speaking only SEL protocol need DNP3 SCADA integration
- Multiple relays per substation need data concentrated to one DNP3 outstation
- Substation automation logic needs to run locally independent of SCADA
- Operators need local visibility without a full SCADA workstation
RTAC vs PLC
RTAC is purpose-built for power systems with native SEL protocol, DNP3, IEC 61850, and pre-built protection function blocks. A PLC requires custom programming for these protocols. See Allen-Bradley PLC for comparison.
RTAC vs SCADA Server
RTAC runs locally at the substation. SCADA servers (Ignition, Geo SCADA) are centralized and poll many substations. RTAC feeds data up to the SCADA server.
Deployments
- Transmission substations
- Distribution substations (feeder automation)
- Industrial facilities (motor control, protection)
- Renewable energy sites
- Data centers (critical power control)
Frequently Asked Questions
Collects relay data via multiple protocols, concentrates it, serves it to SCADA, runs automation logic, and provides a local HMI.
Not a conventional PLC — purpose-built for power systems with native protection protocol support and multi-protocol gateway capability alongside IEC 61131-3.
SEL-3530 is established. SEL-3555 adds secure boot, TPM, and updated cryptography for NERC CIP.