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conventional lightning protection shielded building

w w

direct lightning strike d r
d r d w
d w

nearby lightning strike

s a s a

Figure 9.32.3 Shielding of structures by using natural components of the building

Since in practice the lightning current splits between the in- exactly defined, that is it must be installed at the transition
dividual down conductors depending on the impedances, the from LPZ 0 B to LPZ 1. This prevents dangerous surges from en-
safety distance must be calculated separately for the relevant tering Ex zone 0 or 20 since the interference has already been
building / installation as per IEC 62305-3 (EN 62305-3). discharged. The availability of the temperature transmitter,
which is important for the process, is considerably increased.
Shielding of buildings In addition, the requirements of IEC 60079-11 (EN 60079-11),
Another measure of the lightning protection zone concept is to IEC 60079-14 (EN 60079-14) and IEC 60079-25 (EN 60079-25)
shield buildings. To this end, metal facades and reinforcements must be observed (Figure 9.32.4):
of walls, floors and ceilings on or in the building are combined
to form shielding cages as far as practicable (Figure 9.32.3). ¨ Use of surge protective devices with a minimum discharge
By electrically interconnecting these natural metal compo- capacity of 10 impulses of 10 kA each without damaging
nents of the object to be protected to form closed shielding the equipment or interfering with the surge protective effect.
cages, the magnetic field is considerably reduced. Thus, the
magnetic field can be easily decreased by a factor of 10 to 300 ¨ Installation of the surge protective device in a shielded me-
and an infrastructure for EMC protection can be established tallic enclosure and earthing by means of a copper earthing
2
at low costs. When retrofitting existing installations, the room conductor with a cross-section of at least 4 mm .
shielding must be adapted to the EMC requirements, for exam- ¨ Installation of the lines between the arrester and the equip-
ple, by means of reinforcement mats. ment in a metal pipe earthed on both ends or use of shield-
ed lines with a maximum length of 1 m.
Surge protection in hazardous areas
The lightning protection and Ex zones are already harmonised According to the definition in the protection concept, the LPC
at the design stage. This means that the requirements for the in the control room is defined as LPZ 2. A surge protective de-
use of surge protective devices both in hazardous areas and at vice is also provided at the transition from LPZ 0 B to LPZ 1
the boundaries of lightning protection zones must be fulfilled. for the intrinsically safe measuring line from the temperature
Consequently, the place of installation of the surge arrester is transmitter. This surge protective device at the other end of

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