Purpose of Earthing or Grounding
When an electrical fault develops in domestic applications, any metal parts that the user is in contact with may become live electrical conductors and cause an electrical shock. Adequate earthing of that metal part, however, can provide an unfailing circuit path away from the user to an earth ground, preventing the shock.
If the circuit is protected by a ground-fault circuit breaker, the fault will trigger the tripping of the breaker and remove both the current and the shock potential.
In industrial applications, the condition of earth resistance or leakage current testing may have been neglected, perhaps for a long time, because of the time consuming methods involved, ignoring existing earthing measurement predictive plans, or the non-availability of good testing instruments. This condition can be so bad that it can cause transformer failures and erratic meter readings at high tension feeders, etc., leading to major accidents.
Other than the protection of humans and equipment, the purpose of earthing is to provide a safe path for the dissipation of fault currents, lightning strikes, static discharges, EMI and RFI signals, and interference.
Prior to selecting the location of a substation or commercial sector, it is necessary to measure the soil resistance value.