SEL Settings Groups and SELOGIC Control Equations
Key Takeaway
How SEL settings groups and SELOGIC control equations work — Boolean logic programming, relay word bits, trip logic, and custom automation in SEL relays.
Quick Answer
SEL relays support up to 6 settings groups for different operating conditions. SELOGIC control equations use Boolean algebra (AND, OR, NOT) to combine relay word bits into trip, alarm, and output logic — the programming language for defining how an SEL relay responds to power system events.
Settings Groups
Each group contains a complete set of protection settings. Switch between groups via input contact, SCADA command, or logic. Example: summer vs winter line ratings.
SELOGIC
SELOGIC uses Boolean operators: AND (*), OR (+), NOT (/). Relay word bits represent protection element states (51P, 50P), inputs (IN1, IN2), outputs (OUT1), and internal flags (V1-V8).
Example Trip Logic
TRIP = 51PT + 50P + 27 + 81Trip on phase time-overcurrent OR instantaneous overcurrent OR undervoltage OR underfrequency.
Relay Word Bits
- Protection — 51P (phase OC pickup), 51PT (phase OC trip), 50P (instantaneous)
- Inputs — IN1, IN2 (binary input contacts)
- Outputs — OUT1, OUT2 (relay output contacts)
- Virtual — V1-V8 (internal logic flags)
- Timers — TL1, TR1 (set/reset timers)
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Frequently Asked Questions
SEL's built-in programmable logic using Boolean algebra expressions to combine relay word bits into trip, alarm, and output logic.
Most SEL relays support 2-6 settings groups, each with independent protection settings.
Boolean variables representing protection element states, binary inputs, outputs, timers, and virtual flags — the building blocks of SELOGIC equations.
Still have questions about your setup? Talk to an engineer or call (210) 405-4248.