IEC 61131-3 Programming in SEL RTAC — Overview
Key Takeaway
How IEC 61131-3 programming works in the RTAC — supported languages, task configuration, SEL power system function block library, and program organization.
Quick Answer
The RTAC supports Ladder Diagram, Structured Text, and Continuous Function Chart (CFC) — SEL's FBD-style editor. Sequential Function Chart (SFC) is not a listed RTAC editor. Programs run in cyclic or event-driven tasks accessing RTAC tags. SEL provides a pre-built power system function block library for protection and automation schemes.
Languages
- Ladder Diagram — Discrete control, interlocking
- Structured Text — Complex calculations, state machines
- Continuous Function Chart (CFC) — Analog processing, PID control (FBD-style)
Tasks
Cyclic tasks execute at fixed intervals (e.g., 100ms). Event tasks trigger on tag value changes. Task priority controls execution order.
SEL Power System Library
Pre-built blocks: POTT scheme, breaker failure, reclosing, synchronism check, Volt/VAR optimization, load drop compensation. Validated logic reduces programming time.
Tag Access
All IEC 61131-3 programs access RTAC tags by name. Check tag quality (GOOD/BAD) before using values in control logic.
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Frequently Asked Questions
Ladder Diagram, Structured Text, and Continuous Function Chart (CFC). SFC is not a listed RTAC editor. Different programs can use different languages in the same project.
Pre-built IEC 61131-3 blocks for POTT, breaker failure, reclosing, synchronism check, Volt/VAR optimization — validated SEL logic reducing custom programming.
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