SYSTEM OF GROUNDING

A ground system is constituted from all the elements necessary to connect a circuit, one mass, one mass stranger to the land in order to obtain one more or of the following scopes:

a) offering one via of closing to low resistance to the dispersion currents towards ground in systems TT in order facilitating the participation of the apparatuses of interruption of the breakdown;

b) to bind to it upgrades them of earth a point of a circuit that can be the center star of the cabin transformer (arranges TT and TN), the secondary one of one transformer etc, in order to determine in way univoco the nominal tension towards earth for requirements to the ends works them;

c) to limit the tension total towards earth of a mass in damage in a system IT in case of first breakdown;

d) to bind to it upgrades them of earth a mass or a mass stranger to the aim to control the state of isolation regarding an electrical system isolated from earth (arranges IT or protection by means of separation electrical worker)

Fig. 4,1 earth Systems for: a) guaranteeing a distance to low resisti  to the dispersion currents towards earth; b) to bind to it upgrades them of earth the nucleus of a transformer

Moreover earth systems are had for:

- the elimination of electrostatic charges;

- the operation of special circuits monothread with return to earth (railroads, tramvie);

- the protection against the atmospheric scariche.

The earth system dealt in this issue is adapted to the function of protection against the indirect contacts in the utilizzatori systems in low tension (cat. 0 and I). Saying system, in the respect of Norm CEI 64-8/4, must be only for simultaneously accessible masses.

Fig. 4,2 Ulterior applications of the earth system; as an example for the elimination of the electrostatic charges and/or for the protection against the atmospheric scariche