The Mathematical Formula for Calculating Earth Resistance

Earth Resistance Calculation Formula | ES Grounding Blog

Slamat Asked:
What is the mathematical formula for calculating the resistance-to-ground of parallel electrodes?

 

Our Answer:
The simplified calculation for predicting the resistance-to-ground (earth) of a given length grounding rod is:

R=(p/(2*pi*L))*(ln*(4L/a)-1)) + (p/(2*pi*s))*(1-(L squared/3s(10X8)) + (2L(10×4)/5s(10×4)…)

Where:

  • R= Resistance
  • p= soil resistivity
  • L = Length of the rod
  • a= radius of the rod
  • ln= natural log
  • s = rod spacing

The above is the hand formula, however it does not take into account multi-layered soils.  We highly recommend using a computer program such as CDEGS.

The Engineering Experts at E&S Grounding Solutions

 

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