A Grounding System has two fundamental functions:

a) Providing a neutral return line for currents if a grounding fault occurs.
b) In case of grounding fault, guaranteeing that metallic structures and the accesible environment aren´t exposed to dangerous voltages.

Grounding systems must be verified before start-up and periodically. Step and touch potentials measurement is mandated by regulation and as a reliable way of checking the above-mentioned functions.

This trial consists in injecting a normalized value of current between the analyzed grounding grid and a contra-electrode located at a proper distance. In this situation, the resultant potentials are measured in a number of points representing both interior and exterior of the electrical installation.

The values obtained from the testing current referred, by extrapolation, to the resulted values at fault current. The comparison of the above mentioned values with the admissible ones (according to the regulation) will allow to verify the fulfillment of aforementioned requirements.