Protective Relay Coordination / TCC Visualizer

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.

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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.

• 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