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rosion cell actually present can be recognised by the fact that This particularly also applies to short connecting cables in the
it has the more negative potential when the conductive metal immediate vicinity of the foundations or fixed earthing termi-
connection is opened. When combined with buried steel instal- nals.
lations, the earth electrode materials bare copper, tin-plated
copper and high-alloy stainless steel always behave as cath- Installation of isolating spark gaps
odes in (covering) soils. As already explained, it is possible to interrupt the conductive
connection between buried installations with very different
potentials by integrating isolating spark gaps. It is then nor-
Steel reinforcement of concrete foundations mally no longer possible that corrosion currents flow. In case
The steel reinforcement of concrete foundations can have a of a surge, the isolating spark gap trips and interconnects the
very positive potential (similar to copper). Earth electrodes and installations for the duration of the surge. However, isolating
earthing conductors directly connected to the reinforcement spark gaps must not be installed for protective and operational
of large reinforced concrete foundations should therefore be earth electrodes since these earth electrodes must always be
made of stainless steel or copper. connected to the installations.

Minimum dimensions
Material Configuration Earth rod Ø Earthing conductor Earth plate
[mm] [mm ] [mm]
2
Stranded 50
Solid round 15 50
Copper, Solid tape 50
tin-plated copper Pipe 20
Solid plate 500 x 500
Lattice plate c) 600 x 600
Solid round 14 78
Pipe 25
Hot-dip Solid tape 90
galvanised steel Solid plate 500 x 500
Lattice plate c) 600 x 600
Profile d)
Stranded 70
Bare steel b) Solid round 78
Solid tape 75
Solid round 14 50
Copper-coated steel
Solid tape 90
Solid round 15 78
Stainless steel
Solid tape 100
a) Mechanical and electrical characteristics as well as corrosion resistance properties must meet the requirements of the IEC 62561 series.
b) Must be embedded in concrete for a minimum depth of 50 mm.
c) Lattice plates should be constructed with a minimum total conductor length of 4.8 m.
2
d) Different profiles are permitted with a cross-section of 290 mm and a minimum thickness of 3 mm.
e) In case of a type B foundation earth electrode, the earth electrode shall be correctly connected at least every 5 m with the reinforcing steel.
Note: According to the German DIN 18014 standard, the earth electrode must be connected to the reinforcement at intervals ≤ 2 m.
Table 5.5.8.1 Material, configuration and minimum dimensions of earth electrodes a) e) according to Table 7 of IEC 62305-3 (EN 62305-3)

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