Optimal design of earthing system for high voltage and extra high voltage AC substations

The earthing system of a substation shall be optimal, safe and economical. Accurate measurement of soil resistivity, proper analysis of soil resistivity measurements, optimal grid spacing, proper assumption off ault currents, analysis with two or multi layers soil model play important roles in optimal, safe and economical design of earthing system of a high voltage or an extra high voltage substation.

The paper describes different aspects of designing optimal, safe and economical earthing mat of a high voltage or an extra high voltage AC substation in POWERGRID. The methodology of optimizing quantity of main Earthmat and risers by optimally designing the grid spacing where the substation area is very large and the soil resistivity is very low with homogeneous type soil or by adopting satellite Earthmat or deep driven vertical electrodes in hilly area where the area of the substation is considerably less and the soil resistivity is relatively high and non-uniform have been elaborated.