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Fermenters made of metal sheets by additional air-termination systems to avoid melting at the
Fermenters made of metal sheets typically have a thickness point of strike. For this purpose, an isolated lightning protec-
between 0.7 mm and 1.2 mm. The individual metal sheets are tion system is installed. The rolling sphere method is used to
screwed together (Figure 9.3.6). determine the arrangement of the air-termination system. The
If metal sheets are to be used as natural air-termination sys- down conductor is routed along the metal sheets by means
tem, the metal sheets must have the relevant thickness listed of spacers according to the calculated separation distance
in Table 3 of IEC 62305-3 (EN 62305-3). If the thickness of (Figure 9.3.7).
the metal sheets does not comply with Table 3 of IEC 62305-3
(EN 62305-3), a lightning strike may cause melting or imper- Steel container
missible heating at the point of strike resulting in a risk of fire Figure 9.3.8 shows a biogas tank enclosed by fully
and explosion. In this case, these fermenters must be protected welded steel sheets. According to Table 3 of IEC 62305-3

Summation difference technical room
measurement CHP
grid infeed control unit

3 x 20 kV

MEB MEB G ~ M

storage
tank

grain silo

liquid
container
collection M ~ ϑ
pit
fermenter post-fermenter

Protection for the Part No. Protection for the Part No.
earth-termination system earth-termination system
Strip made of stainless steel (V4A), 860 335 Equipotential bonding bar made of stainless 472 209
30 mm x 3.5 mm, or round wire made of 860 010 steel (V4A) or earthing busbar 472 139
stainless steel (V4A), Ø 10 mm
Cross unit made of stainless steel (V4A) or 319 209 Terminal lug in the form of a flat strip made of 860 215
SV clamp made of stainless steel (V4A) 308 229 stainless steel (V4A) or terminal lug in the form 860 115
Note: Anti-corrosive band 556 125 of a round wire made of stainless steel (V4A)
Figure 9.3.9 Intermeshed earth-termination system for a biogas plant

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