Page 420 - 35_DS702_E_2014_Lightning_Protection_Guide

DEHN (Figure 9.28.3). This is particularly required for shelters circumstance. Moreover, adequate measures must be taken
that are even smaller than those described above. to prevent that plants grow through the shelter (Figure
9.28.4).
Prevention of step voltages
Dangerous high step voltages resulting from a lightning strike b) Prevention of step voltages by means of potential control
to the lightning rod of a shelter or a nearby lightning strike
must be prevented in shelters. There are two options: Another protection measure is potential control, namely
the integration of a finely meshed metal grid (e.g. reinforce-
ment steel mat laid in concrete or a buried meshed earth
a) Prevention of dangerous step voltages by insulating the electrode with a mesh size smaller than 0.25 m x 0.25 m)
floor directly in the ground below the standing surface of per-
This means that the floor must be covered by e.g. a 5 cm sons. To ensure a long service life of this metal grid, it is
asphalt layer. As an alternative, a wood floor can be used advisable to use 10 mm round conductors made of stain-
that maintains a sufficient distance from the ground to less steel (V4A) (e.g. material number AISI/ASTM 316 Ti).
ensure adequate ventilation and that remains dry in any These round conductors are installed max. 0.1 m below the

down conductor
air-termination rod

CUI Conductor CUI Con-
ductor

potential potential
control control

earth rod equipotential bonding conductor earth rod

Figure 9.28.3 Installation of a high-voltage-resistant CUI Conductor: a) in case of a small shelter with two air-termination rods; b) in case of
insufficient wall thicknesses

5 cm asphalt with an incli- down conductor wood floor down conductor
nation towards the entrance

earth rod

measures to prevent
equipotential equipotential e.g. elevated position for that plants grow
earth rod bonding conductor bonding conductor gravel bed sufficient ventilation through the shelter

Figure 9.28.4 Insulation of the standing surface to prevent step voltage: a) by means of asphalt; b) by means of a wood floor

www.dehn-international.com LIGHTNING PROTECTION GUIDE 419