When performing tests on IEC 61850-based substations, understanding the IED’s Mode and Behavior is what separates a safe test from an operational risk.
Why is this critical?
The main objective is to avoid incorrect actions, such as an accidental trip, during testing, keeping the logic active but controlling the outputs.
Essential difference
• Mode: is what you configure in the IED;
• Behavior: is what you read back (read only), reflecting the effective state of the equipment considering the hierarchy and constraints.
In other words: you request the Mode, but it is the Behavior that confirms how the IED is actually operating.
Main Mode States
Each mode defines how the output contacts behave:
• On: contacts operate normally
• Blocked: contacts do not operate
• Test: logic processes signals, and outputs continue operating
• Test/Blocked: logic processes, but outputs are blocked
• Off: no processing
