A model for determination of galvanically separated grounding grids and grounding systems has been presented in this work. Determination of the above also means determination of the grounding resistances, the potentials of the grounding grids, currents of leading to earth from the separated electrodes, distribution of the potentials along the surface of the earth etc. The exposed model is based on the application of Maxwell's equations, based on the formal analogy that exists between the quasi-stationary current field and electrostatic field. The model is also applicable for grounding grids in an inhomogeneous environment.