Examples of Practical Minimum Dimensions - RME111 - AWS310-SITE - RWCC - AWS310 - AWS430 - RWS200 - FOC201

Grounding and Lightning Protection in Vaisala Outdoor Installations Technical Reference

Document code
M211786EN
Revision
B
Language
English (United States)
Product
RME111
AWS310-SITE
RWCC
AWS310
AWS430
RWS200
FOC201
Document type
User guide

The following minimum material dimension values are widely used and field-proven to conduct lightning currents to ground without excessive heating or physical damage in majority of installations. These dimensions may not fulfill national or international standards.

Table 1. Air Terminal Minimum Dimensions
Material Dimension
Copper, aluminum Tube with a 16 mm (0.63 in) diameter, minimum wall thickness of 2 mm (0.08 in)
8 mm (0.31 in) solid round
Steel 10 mm (0.39 in) steel
Table 2. Down Conductor Minimum Dimensions
Material Dimension
Copper 25 mm2 (AWG 4) solid or stranded wire or solid tape
Aluminum 35 mm2 (AWG 2) in solid or stranded aluminum
Steel 35 mm2 (AWG 2) solid steel or stranded wires
Table 3. Minimum Thickness of Tapes
Material Thickness
Copper 1 mm (0.04 in)
Aluminum 2 mm (0.08 in)
Galvanized steel 2 mm (0.08 in)
Stainless steel 2 mm (0.08 in)
Table 4. Minimum Thickness of Strand Diameters in Stranded Cables
Material Thickness
Copper 1 mm (0.04 in)
Aluminum 1.6 mm (0.06 in)
Steel 1.6 mm (0.06 in)

Table 5 and Table 6 show two examples of practical minimums for ground electrodes. The materials are preferred because they are fairly corrosion-resistant, not because they provide optimum conductivity.

The following table is applicable to an arrangement of three ground rods in a triangle layout at 6-m (20-ft) spacing.

Table 5. Ground Rod Minimum Dimensions
Material Thickness
Copper Solid round 15 mm (0.59 in)
Pipe 20 mm (0.79 in) diameter with a minimum wall thickness of 2 mm (0.08 in)
Copper clad solid steel 14 mm (0.55 in)
Galvanized steel 16 mm (0.63 in)
Galvanized steel, pipe 25 mm (0.98 in) diameter with a minimum wall thickness of 2 mm (0.08 in)

The following table is applicable to an arrangement of three 10-m (33-ft) horizontal ground electrodes in Y-shape.

Table 6. Horizontal Ground Electrode Minimum Dimensions
Material Thickness
Cu 25 mm2 (AWG 4) solid/strand/tape with a minimum 2 mm (0.08 in) thickness
Galvanized steel, round wire 50 mm2 (AWG 1) with a minimum 8 mm (0.31 in) diameter
Galvanized steel, stranded 50 mm2 (AWG 1) with a minimum strand diameter of 1.7 mm (0.07 in)
Galvanized steel, tape 50 mm2 (AWG 1) with a minimum thickness of 2 mm (0.08 in)