Protection Zone & Relay Scheme Explorer

Protection engineering is one of the most consequential disciplines in power systems, and understanding which relay trips for which fault — and which backup trips if the primary fails — requires a mental map of zone overlap, relay reach, and coordination hierarchy that is difficult to build from textbook reading alone. This explorer builds that map visually. Choose a system topology (Utility→Feeder→Transformer→Load, Main-Tie-Main Lineup, Simple Substation, or Feeder with Motor Load), then explore the protection zone diagram showing every relay's coverage area and responsibility boundary. The Settings Lab tab lets you adjust relay settings and see how pickup and time-dial changes affect coordination. The Scenario tab injects six guided fault events — Feeder Fault, Bus Fault, Transformer Internal Fault, Downstream + Primary, Primary Fails → Backup, and Breaker Failure — and shows which relays operate, which are restrained, and what the sequence of events looks like. The Challenge tab presents protection design problems with graded results. The Responsibility tab maps each relay ANSI function to the equipment it protects.

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A live look at the app you'll launch — every control on the left drives the visualizations on the right in real time.

• 01Draw and describe the protection zone boundaries for feeder, transformer, and bus protection in a simple substation
• 02Explain why adjacent protection zones intentionally overlap and how overlap prevents unprotected gaps
• 03Trace the sequence of relay operations for a feeder fault, bus fault, and transformer internal fault
• 04Describe the breaker failure scenario and identify which backup protection operates if a primary breaker fails to clear
• 05Adjust relay pickup and time-dial settings in the Settings Lab and predict the effect on coordination margin
• 06Identify which ANSI relay functions are assigned to each protection zone in a Main-Tie-Main lineup