This simulator explores what happens when fault current returns to earth through a substation grounding system, using an explicitly simplified uniform-soil hemispherical model. Adjust the fault current, soil resistivity, electrode geometry and bonding, then watch ground potential rise and the surface-potential field respond — and see why earth is not zero volts during a fault.
• A real-time 3D grounding scene — current injection, the buried ground electrode, a surface-potential field, bonded accessible equipment, measurement positions for step and touch voltage, and a remote-earth return reference — with camera home view, focus-selected-part, toggleable enclosure, auto-rotate, expand and tap-to-inspect components. • Six live controls: applied ground-fault current (100–10,000 A), uniform soil resistivity (10–1,000 Ω·m), equivalent electrode radius (0.5–30 m), percentage of current entering local soil (0–100%), equipment bond resistance (0–0.1 Ω), and fault duration (0.1–2 s). • Play/pause, single step, larger step, and 0.1×/1×/10×/60× playback speed. • Actions to apply a timed ground fault and to clear the fault immediately. • A Potential profile analysis tab with two live charts, the underlying model equations (spreading resistance, surface potential, ground potential rise, step and touch voltage, body current), and snapshot measurements. • A Test & diagnose style Experiments tab with four guided experiments, an independent model-verification bench, and a timestamped event log with a copyable trial report. • A Learn & assess tab with guided lessons, a knowledge-check quiz and a written scope statement with a reference link. • Live metrics for local earth current, other metallic return current, equivalent spreading resistance, ground potential rise, equipment bond drop, and bond heating energy.
When a fault injects current into the grounding system, only part of it returns through local soil — the rest can return through other metallic paths such as shield wires, neutral conductors or pipes, which is why the simulator lets you split the fault current between the two. The current that does enter local soil sees a spreading resistance set by soil resistivity and the equivalent electrode radius (Rg = ρ / 2πa in this hemispherical approximation), and that resistance times current produces a ground potential rise — the grounding system's voltage relative to remote earth, which is treated as the zero-volt reference far from the fault.
Outside the equivalent electrode radius, surface potential falls off approximately as 1/r; inside that radius, this teaching model holds potential uniform. Step voltage compares two earth positions the same person might stand between, while touch voltage compares grounded, bonded accessible metal — which sits at ground potential rise plus the equipment's own bond drop — against the earth beneath a person's feet. Both differences drive a hazard current through an assumed fixed body-plus-contact resistance.
The analysis tab plots the surface-potential field so you can see the ground potential rise decay with distance and how raising soil resistivity, shrinking electrode radius, or reducing the local-earth-current split each change the numbers — for example, holding current and geometry fixed while multiplying soil resistivity by five multiplies surface potentials by five as well, directly following the 1/ρ relationship in the equations.
This is explicitly a homogeneous, quasi-static hemispherical model with a constant-potential interior — it is a teaching fixture, not an IEEE 80 ground-grid calculation, and it does not model real mesh voltage gradients, multilayer soils, transferred potentials, or exposure variability. The body-circuit resistance is fixed rather than representing physiological injury thresholds, no green/safe classification is ever made, and a zero modeled difference in this simulator does not establish that any real location is safe — a site-specific grounding and exposure study is required for an actual installation.
When fault current flows into the grounding system, the portion that enters local soil must push through the soil's spreading resistance to reach remote earth. That resistance times current produces a real voltage — the ground potential rise — meaning the local grounding system, and everything solidly bonded to it, sits above the voltage of remote earth for as long as the fault persists.
Step voltage is the potential difference between two earth surface positions a person might stand between, such as two foot placements a stride apart. Touch voltage is the potential difference between accessible bonded equipment — which sits at ground potential rise plus its own bond drop — and the earth beneath a person's feet while touching that equipment. Both differences can drive current through an assumed body-plus-contact resistance.
In this model, spreading resistance and surface potential are both directly proportional to soil resistivity. Multiplying soil resistivity by five, holding fault current and electrode geometry fixed, multiplies the ground potential rise and surface potentials by roughly five as well, which the built-in higher-soil-resistivity experiment demonstrates directly.
No. It is an explicitly simplified, homogeneous, quasi-static hemispherical soil model with a constant-potential interior, built for teaching the underlying relationships, not an IEEE 80 ground-grid calculation. It omits real mesh gradients, multilayer soils, transferred potentials and exposure variability, uses a fixed body-circuit resistance rather than physiological injury thresholds, and never issues a safe/unsafe classification — a real installation requires a site-specific engineering assessment.