SEL Settings Groups and SELOGIC Control Equations

Quick Answer

Many SEL relays support multiple settings groups (commonly up to six) for different operating conditions. SELOGIC control equations combine Relay Word bits into trip, alarm, and output logic — the programming language for defining how a 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 operators

Operator syntax depends on the relay generation. Classic SELOGIC Boolean equations commonly use * for AND and + for OR, with ! or the NOT operator for inversion. Modern SEL-700-series style equations typically use the words AND, OR, and NOT. Do not treat / as Boolean NOT — on many platforms / is arithmetic division in math equations. Always follow the SELOGIC operator table in your relay instruction manual.

Example Trip Logic (classic * + style)

TRIP = 51PT + 50P + 27 + 81

Trip 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; naming varies by model)
• Outputs — OUT1, OUT2 (relay output contacts)
• Latches / SV bits — Internal logic flags and SELOGIC variables (count and names vary by model)
• Timers — SELOGIC timers (SV/PC/TL naming varies by platform)