Specifications

Schneider Electric

Review

(continued)

To be effective, an underground network must be in the form of a grid:

For small premises (less than about 10 m

), a simple buried perimeter ring is

sufﬁcient.

For new buildings of large surface area, the installation of buried conductors in the

form of a grid with a 10 m mesh size is recommended.

For areas housing equipment that is highly sensitive to electromagnetic

disturbances, the mesh size should be no more than 2 m.

Definition:

An equipotential grounding is formed by connecting all metal structures

of the installation (frames, handrails, ducts, etc.).

Physically speaking, it is more important to obtain the local equipotentiality of the

building than a low resistance (with respect to a distant earth).

The most sensitive lines are those that interconnect the various items of equipment.

In order to limit the flow of common mode currents in the cables that do not leave the

building, it is necessary to limit the voltages between interconnected equipment

within the site.

Building earthing ring Earth connection bar

E52272

Cabling Guidelines