Designs a substation/site earthing (grounding) grid per IEEE Std 80: grid resistance, ground potential rise (GPR) and the tolerable touch/step voltage safety limits people must be protected against during a ground fault, plus BS 7430 single-electrode resistance formulas for rods, plates, strips and rings.
Standards followed
IEEE Std 80 (guide for safety in AC substation grounding)BS 7430 (code of practice for protective earthing of electrical installations)
What it can do
- Grid resistance (Sverak formula) and ground potential rise from soil resistivity, grid geometry and fault current.
- Tolerable touch and step voltage limits from body weight and fault clearing time.
- Surface layer derating (crushed rock, asphalt, concrete, gravel) to raise tolerable limits.
- Single electrode resistance for rod, plate, strip and ring geometries (BS 7430).
- Advanced: the actual mesh (Em) and step (Es) voltage pass/fail check against the tolerable limits, plus two-layer soil, parallel electrodes and transferred (offsite) potential.
Example problem
Analyze a default 30m×20m grid with 4×3 conductors, 100 Ω·m uniform soil, and a 10kA ground fault.
- Compute grid resistance Rg from the Sverak formula using grid area, conductor length, and burial depth.
- Compute ground potential rise GPR = fault current × Rg.
- Compute tolerable touch and step voltage limits from body weight and fault clearing time.
- Compare (on the advanced) actual mesh voltage Em and step voltage Es against those tolerable limits.
The default grid configuration (no surface layer, no mitigation) correctly flags as unsafe — the calculation chain from Rg through GPR to Em/Es pass/fail was confirmed internally consistent end to end.
Want the full step-by-step version?
The core computes Rg/GPR and the tolerable limits themselves, but not the actual mesh/step voltage pass/fail verdict — that comparison is part of the advanced mesh/step check.