Page 201 - Electrical Safety of Low Voltage Systems

184 Chapter Eleven

Steel
Cross-
Electrode’s Diameter Sectional Thickness
2
Surface Type (mm) Area (mm ) (mm)
Hot-dip Strip — 90 3
galvanized
or stainless
Round rod for 16 — —
deep earth
electrodes
Round wire for 10 — —
surface earth
electrodes
Pipe 25 — 2

TABLE 11.2 Minimum Sizes of Common Electrodes Made of Steel

In this respect, common minimum sizes for earth electrodes, as per
2
IEC 60364–5-54, are reported in Tables 11.2 and 11.3. The two tables
allow a comparison between the two commonly used materials, steel
and copper, in terms of equivalent withstand capability to corrosion
and mechanical strength as a function of their type and dimensions.
We have already mentioned the possibility of using the concrete-
encased reinforcing steel bars of a building’s footings as an electrode.

Copper
Electrode’s Diameter Cross-Sectional Thickness
2
Type (mm) Area (mm ) (mm)
Bare strip — 50 2
Bare rope 1.8 for individual 25 —
strands
Bare round — 25 —
wire for
surface
earth
electrodes
Bare pipe 20 — 2
Tin-coated rope 1.8 for individual 25 —
strands
Zinc-coated — 50 2
strip
TABLE 11.3 Minimum Sizes of Common Electrodes Made of Copper