Protective Relay Coordination / TCC Visualizer

Plot upstream and downstream IEC IDMT relay, breaker, and fuse curves on a live TCC — then verify CTI margin, inject fault current, and step through the trip sequence using six preset coordination scenarios.

AVAILABLEAUTOMATED CHECKS ONLYSTANDARDS-AWAREADVANCEDIEEEWHAT DO THESE STATUSES MEAN?

IEC IDMT CURVES6 PRESET SCENARIOSCTI MARGIN CHECKTRIP SEQUENCE ANIMATOR

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Overview

Protective relay coordination is the discipline of ensuring that the device closest to a fault operates first and that upstream devices operate only as backup — and the time-current characteristic (TCC) plot is where that guarantee lives or dies. This visualizer puts you in control of a live TCC: configure a downstream device and an upstream device independently, selecting from IEC IDMT relay curves (Standard/Normal Inverse, Very Inverse, Extremely Inverse, Definite Time), generic breaker overcurrent, or generic fuse approximation. Set pickup current and time multiplier setting (TMS) for each, add instantaneous elements and ground fault settings, then inject fault current to see both curves simultaneously and evaluate CTI (coordination time interval) margin. The Trip Sequence tab animates the trip event — showing which device clears the fault and how quickly. The Dashboard shows one-line context, global scan status, notes and recommendations, and a real-time event log. Six preset scenarios cover Well Coordinated, Marginal, Overlap/Conflict, Fuse-Breaker (Educational), High Fault, and Ground Fault conditions, each designed to illustrate a specific coordination challenge. The Learn tab covers TCC reading, pickup, TMS, IEC 60255 curve families, coordination principles, motor/transformer inrush behavior, and common coordination mistakes.

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

TCC Visualizer dashboard — Dashboard — global scan status, one-line context, notes & recommendations, and a live event log tie every setting change back to a coordination outcome.

TCC View with dual device curves — TCC View — plot the downstream and upstream device curves together, drop a fault-current cursor, and read CTI margin directly off the chart.

Trip sequence animation — Trip Sequence — animate the clearing event to see which device operates first and how much time the upstream backup has in reserve.

Coordination scenario presets — Scenarios — six presets (Well Coordinated, Marginal, Overlap, Fuse-Breaker, High Fault, Ground Fault) each staged to illustrate a specific coordination challenge.

Learn tab covering TCC theory — Learn — TCC reading, pickup, TMS, IEC 60255 curve families, inrush handling, and the most common coordination mistakes, with a quiz to check yourself.

What you'll do

01Read a time-current characteristic curve and identify the pickup, time-delay, and instantaneous regions for both upstream and downstream devices
02Explain coordination time interval (CTI) and determine whether adequate margin exists between two overlapping curves
03Set IEC IDMT curve parameters (pickup and TMS) for Standard, Very Inverse, and Extremely Inverse curves and predict the resulting trip time at a given fault current
04Describe why an instantaneous element must be set below the minimum fault current seen by the upstream device
05Step through a trip sequence and identify which device clears a fault first under each of the six preset scenarios
06Explain why generic fuse curves in educational tools cannot substitute for manufacturer TCC data in a real coordination study

Try a guided scenario

Coordinate a downstream and upstream device across the fault range.

Time-current coordination · 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).