Earthing is the process of transferring electrical energy directly to the earth by the help of the low resistance wire. The earthing is an essential part of buildings and some infrastructures because it protects humans from high voltage surges and lightning discharge. Proper earthing minimizes the danger of high step or touch voltages in critical operating areas or places that are frequently used by people. Thus, properly designed earthing systems capable of dissipating large currents safely to earth is required in mid- and high-voltages installations.
Earthing can be done by electrically connecting the respective parts in the installation to some system of electrical conductors or electrodes placed near the soil or below the ground level. The earthing mat or electrode under the ground level have flat iron riser through which all the non-current-carrying metallic parts of the equipment are connected.
A proper design of an earthing mat (number and size of electrodes) depends strongly on the electrical properties of the ground nearby. Electrical surveys (VES or ERT) are carried out to determine accurately the electrical resistivity of the ground at a specific point where the earthing needs to be installed. These surveys can also be used to find the most favorable location for the earthing, reducing associated costs by minimizing the required installation.