Protection Zone & Relay Scheme Explorer

Explore protection zones, relay responsibility areas, and scheme behavior across four system topologies — then drive fault scenarios including feeder faults, bus faults, transformer internal faults, backup operation, and breaker failure.

AVAILABLEAUTOMATED CHECKS ONLYSTANDARDS-AWAREADVANCEDIEEEWHAT DO THESE STATUSES MEAN?

4 SYSTEM TOPOLOGIES6 FAULT SCENARIOSSETTINGS LABZONE VISUALIZATION

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Overview

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.

App preview

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

Inside the lab

Example data — not a real field report

Overview tab — Overview · Pick a system topology and browse the relay-type reference before diving into zones.

One-line diagram — One-Line / System · Annotated one-line with every protective device labeled by ANSI function.

Protection zones — Protection Zones · Overlapping zone boundaries for feeder, transformer, and bus protection.

Relay responsibility map — Relay Responsibility · Which relay owns which equipment, mapped by ANSI code.

Relay settings lab — Relay Settings Lab · Adjust pickup and time-dial and watch coordination margin update live.

Scenario lab — Scenario Lab · Six guided fault events including breaker failure and primary-fails-to-backup.

Design challenge — Design Challenge · Graded protection design problems that test zone and coordination thinking.

Learn mode — Learn Mode · Protection scheme fundamentals, ANSI function codes, and zone theory.

What you'll do

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

Try a guided scenario

Change pickup and time dial and observe operating behaviour.

Relay fundamentals · Protection & Relay Coordination

No sign-in required. Progress is saved on this device.

What this lab is not

Not a design document, stamped calculation, or approval record.
Not a substitute for engineering analysis by a licensed professional.
Not a relay setting file and not a coordination study of record.
Not connected to live equipment and not a safety device.

Calculation basis

References IEEE. Results are computed from the entered inputs and cited back to the referencing clause or table number — no code text or table is reproduced verbatim.

Simplifying assumptions are stated in the lab itself; where a model is intentionally conceptual, the lab says so rather than implying study-grade accuracy.

Standards basis: Standards-aware. Validation state: Automated checks only (last checked 2026-08-15).