An earthing system provides a drain path to all kinds of faults that may develop in an electrical system comprising of power circuits, control circuits, EMP and Statics.

The nature of these faults varies with respect to frequency, amplitude and time.

Therefore, the earthing system for such installation needs to be thoughtfully designed to handle all such faults effectively.

Any earth grid should necessarily have the following parameters:

• The earth grid should have the minimum cross section to carry the maximum fault current for particular time duration without fusing
• The actual step potential should be lower than the allowable step potential
• The actual mesh potential should be lower than the allowable touch potential

IEEE 80-2000, IEEE 665, IEEE 142, IEEE 81-1993, BS – 7430, IS 3043 are the standards which provide detailed procedures for designing such a grid.