EPR and Fault Current Split

Earth Impedance (Ω) Return Impedance (Ω) Parallel Impedance (Ω)
Fault Current (kA) Return Current (kA) Ground Return Current (kA)
Earth Potential Rise (EPR) Return Current (%) Ground Return Current (%)

Earth Grid Calculations

Ground Resistivity \(\rho\) (mΩ) \(Area\) (m2) Radius of Circular Plate
of Same Area as Grid \(r\) (m) $$ r = \sqrt{Area \over \pi} $$
Tape Depth \(h\) (m) Total Tape Length \(L\) (m)
Rod Factor \(K_R\) $$ K_R= 1 + {{n_R \times {l_R}^2} \over {10r^2}} $$
Rod Number \(n_R\) Rod Length \(l_R\) (m) Earth Resistance Calculated
with Rods \(R_G\) (Ω): \[R_G=\rho {\left({1+ {\left(r \over {r+2.5h}\right)} \over 8r \times K_R}+{1 \over L}\right)}\]

Ground Resistivity Correction

Earth Resistance \(R\) (Ω)
Corrected Resistivity \(\rho_A\) (mΩ)

$$ \rho_A = {R \times \rho \over R_G} $$