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02/03/ 2012


Proper earthing

 

If you are looking to properly install earthing networks, then you are better off referring to Standard CEI 64-8 part 5, item 542.2 as it expressly talks about these devices, starting from how they can be built. The market offers rods, profiles, tubes, bands, ropes, plates. Nevertheless, an earthing network can also be built using conductors fitted in the foundations, or using the same reinforcement rods of the concrete buried in the soil, or again, using the waterworks metal piping, as long as the water company is aware of it and the person in charge of electric systems is informed of any changes in the waterworks installation. The standard is clear, but the risk of a subsequent lack of information is significant: best to avoid. Just like it is best to avoid using the reinforcement or lead sheathing of cables not subject to damage by corrosion as an earthing network (even if the standard does not exclude it). In case you do so, remember that you need the owner's consent and precise information in case of changes that may affect their use as earthing networks.

 

 

How to install an earthing network

Earthing networks can also be built with underground structures suited to the purposes (certainly not metal piping inflammable gases or liquids, as the standard specifically forbids it). The standard also recommends that the installation of earthing networks directly in rivers, canals lakes, etc. be avoided. In case there is no alternative, it is recommended to install the earthing network at least 5 m below water level and, if necessary, to prohibit access to the potentially dangerous area.

The first recommendation concerns what needs to be done to obtain the highest efficiency from earthing networks. During their installation, proper adherence to the ground must be achieved, connecting the earthing device-protection conductors group to the foreign masses and to the reinforcement irons in reinforced cement (foundations), avoiding damage to any metal parts that may be found in the ground surrounding the earthing network. Be extremely careful to avoid installations that lead to increased earth resistance due to it becoming arid or frozen. It also recommended to install the earthing network so that it can withstand mechanical damages caused by corrosion, and to make sure that said corrosion does not cause an increase in earth resistance.

 

The materials

From a technological standpoint, earthing networks can be made of copper, copper-lined steel or zinc-plated ferrous material, or even of other metallic materials that do not contrast with the physical-chemical characteristics of the soil.

In any event, you need to provide for a section that ensures a suitable service life to the installation, also in reference to the soil and earthing network characteristics mentioned above.

 

A valuable table

Lastly, a useful table is included in the Standard concerning earthing network dimensions.

 

1

2

3

4

5

Electrode type

Dimension

Heat zinc-plated steel (CEI 7-6) (1)
(CEI 7-6) (1)

Copper-lined steel

Copper

For underground installation

Plate

Thickness (mm)

3

X

3

Band

Thickness (mm)

Sezione (mm2)

3

100

X

3

50

Rod or solid conductor

Thickness (mm)

50

X

35

Stranded conductor

Diameter of each wire (mm)

Rope diameter (mm2)

1,8

 

50

X

1,8

 

35

For staking into the ground

Tube-like stake

 

External diameter (mm)

Thickness (mm)

40


2

X

30


3

Solid stake

 

Diameter (mm)

20

15 (2)(3)

15

Stake in profile

Thickness (mm)

Cross-sectional dimension (mm)

5

50

X

5

50

(1) Also steel with no protective lining, as long as the thickness is increased by 50% (minimum section 100 mm2).
(2) Lining for electrolytic deposit: 100 mm.
(3) Lining for drawing: thickness 500 mm.
X = type and dimensions not considered by the Standard.

Table 1 – Conductor dimensions (taken from standard CEI 64-8/5)

 

 


Learn more
- Wikipedia: Proper earthing

 

Rev.15.0126      

 

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