Page 439 - 35_DS702_E_2014_Lightning_Protection_Guide

Protection method Typical
Class Rolling down
of LPS sphere Protective angle α Mesh size conductor
radius r [m] w [m] spacing [m]
α° 80
I 20 70 5 x 5 10
60
50
II 30 10 x 10 10
40
30
III 45 20 I II III IV 15 x 15 15
10
0
IV 60 0 2 10 20 30 40 50 60 20 x 20 20
h [m]
Table 9.32.1 Arrangement of air-termination systems according to the class of LPS

Down conductors
Down conductors are electrically conductive connections be-
tween the air-termination system and the earth-termination
air-termination system, system. To prevent damage when conducting the lightning
e.g. telescopic lightning current to the earth-termination system, the down conductors
protection mast
must be arranged in such a way that
¨ There are several parallel current paths between the point
tank
of strike and earth (systems in hazardous areas: one down
s conductor for every 10 m of the perimeter of the outer roof
edges, however, at least four),
¨ The length of the current paths is as short as possible,
¨ Connection to the equipotential bonding system is estab-
lished wherever necessary.
¨ An equipotential bonding system at ground level at inter-
vals of 20 m has proven its worth.

earth-termination system The reinforcements of reinforced concrete buildings may
(ring earth electrode) also be used as down conductors if they are permanently
interconnected in such a way that they can carry lightning
Figure 9.32.2 Air-termination system for a tank with air-termination currents.
rods and air-termination cables
Separation distance
metal pipes and containers can also be used as air-termination If there is an insufficient separation distance d between the
systems if they have a minimum material thickness of 5 mm air-termination system or down conductor and metal and elec-
according to Annex D 5.5.2 of the IEC 62305-3 (EN 62305-3) trical installations inside the structure to be protected, danger-
standard and the temperature rise and reduction of material at ous proximities may occur between the parts of the external
the point of strike do not present additional risks (e.g. reduc- lightning protection system and metal as well as electrical in-
tion of the wall thickness of pressure containers, high surface stallations inside the building. The separation distance d must
temperature at the point of strike) (Figure 9.32.1). not be smaller than the safety distance s (d > s).

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