Injection of a direct current through an above-ground circular plate earth electrode is studied. A non-homogeneous soil having an exponentially decreasing conductivity is considered. The particularities of the problem allow the use of the separation of variables method for solving the homogeneous second order PDE verified by the electric potential. The analytically obtained solution is used to calculate the moduli of the electric strength and of the Poynting’s vector, respectively, and finally the formula of the earth electrode resistance is derived. Taking the limit of this relationship, the homogeneous case formula is also obtained.

Keywords: Earth electrode, Inhomogeneous conductivity soil, Earth electrode resistance