Fault Current & Short-Circuit Simulator

Short-circuit studies are the foundation of equipment selection, protection coordination, and arc flash analysis — yet the per-unit method, X/R ratio, asymmetric DC offset, and sequence network behavior that drive those studies are poorly understood without a tool that shows all the variables interacting. This simulator builds a four-bus radial system: source (0.4–500 kV, Zs 0.01–1.0 pu), transformer (1–100 MVA, 1–15% impedance, with Delta-Wye Grounded, Wye-Wye, or Delta-Delta configuration), cable (0.1–20 km), and a relay (pickup 100–10,000 A, trip time 0.02–2 s). Fault location is selectable across Bus 1 (Source Terminal), Bus 2 (Transformer Secondary), Bus 3 (Feeder Mid), and Bus 4 (Load End). Fault type is selectable: Three-Phase (LLL), Single Line-to-Ground (SLG), Line-to-Line (LL), and Double Line-to-Ground (DLG). Base MVA (10–1,000 MVA) and X/R ratio (1–50) are adjustable for asymmetric first-cycle calculations. The tool computes symmetrical fault current, asymmetric peak, and relay operating time, and shows the per-unit impedance network. The educational content section explicitly states what the tool does and does not model — including no protective device coordination, no arc-in-a-box correction, no motor contribution, and no code-compliant label output — making it honest about its role as a learning tool rather than a study replacement.

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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.

• 01Convert system impedances to a common per-unit base and compute total impedance from source to fault location
• 02Calculate symmetrical three-phase fault current and explain why it sets the upper bound for equipment interrupting ratings
• 03Predict how transformer configuration (Dy vs. Yy vs. Dd) affects zero-sequence current path and SLG fault magnitude
• 04Explain X/R ratio and calculate the asymmetric peak multiplier for first-cycle fault current
• 05Determine how fault current magnitude changes as fault location moves from Bus 1 to Bus 4 due to additional series impedance
• 06Identify what a code-grade short-circuit study includes that this educational tool does not, including motor contribution, arc-in-a-box correction, and coordination modeling