Design standard
Method toggles
Conductor sizing (Onderdonk)
Intermediate Factors
Standards references
This tool implements published IEEE/IEC/GB equations for preliminary grounding grid design. A final design requires site-specific soil resistivity measurements (Wenner/Schlumberger method), full grid model simulation (CYMGRD, WinIGS, or ETAP), and review by a licensed protection/grounding engineer.
Why mesh voltage matters
During a ground fault, fault current flowing through the grounding grid creates voltage gradients across the substation yard. The mesh voltage Em is the worst-case touch voltage experienced by a person standing on the surface and touching grounded equipment. If Em exceeds the allowable touch voltage (which depends on body impedance, surface layer resistivity and fault duration), cardiac fibrillation risk rises sharply. IEEE 80-2013 and IEC 61936-1 both derive allowable limits from IEC TS 60479-1 body-current curves and require Em < Etouch at every mesh corner.
Worked Example — 33/11 kV Primary Substation
50 × 50 m grid (A = 2500 m²) · ρ = 100 Ω·m soil · 100 mm crushed rock (ρ_s = 3000 Ω·m) · I_G = 10 kA · t_f = 0.5 s · 10 conductors/direction · burial h = 0.6 m · hard-drawn copperR_g = 0.227 Ω · GPR = 2 270 V · E_touch = 288 V < 453 V tolerable ✅ · E_step = 624 V < 1 483 V ✅ · Min. conductor 120 mm² Cu (use 150 mm² std)
Need a full grounding study? FrameAI generates stamped substation grounding reports with IEEE 80 / IEC 61936-1 references, Wenner soil model, and fabrication-ready conductor schedule.
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