Resistance to Earth calculations are the basis for other calculation which require the effective soil resistivity at that location. Once this value is obtained grounding charts like Dwight’s curves can be used to determine multiple anodes as required. The calculation is used in the AC Power Tool Program as a basis for a distributed anode mitigation system.
This calculation is just for a single anode which requires other calculations and or charts such as for grounding. It is the basis for other calculations such as multiple or distributed anodes.
where
𝑅 — Anode resistance to earth(Ohms)
𝐿 — Anode length(ft)
𝜌 — Actual soil resitivity(Ohm/cm)
𝑑 — Anode actual diameter(ft)