In a substation, several equipment require connection to the earth at various locations to maintain equipotential platform, hence the need to provide very low resistance path for fault current to flow into the ground is very imperative. This will help to limit the ground potential rise, touch and step potentials within tolerable limits. Substation earthing system is made up of grounding mat, vertically driven electrodes, ground risers and strips to provide the required low resistive path. This paper presents model of a substation earth grid with analytical method of determining the resistances of the meshes and electrodes for proper model representation in Matlab/Simulink. The model is then used for earthing system simulation of 88/22 kV substation to assess its transient performance.