How do you design and analyze a grounding grid for a substation?

Grounding grid design follows IEEE 80 methodology: determine fault current magnitude and duration, calculate soil resistivity from measurements, design grid geometry (conductors spacing 3-10m, depth 0.3-1m), calculate grid resistance using Schwartz or other formulas, verify ground potential rise (GPR) during faults, calculate mesh and step voltages, compare to tolerable limits based on body resistance and fault duration. If limits exceeded, increase grid density, add ground rods, or reduce soil resistivity with chemical treatment. Document for future reference.