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structures which are prone to lightning strikes (e.g. antenna ning protection system: In this case, it is not to be expected
masts, air-conditioning systems). The measuring and control that direct lightning currents occur. A lightning current carrying
or telecommunications cable connecting the terminal device type 1 arrester only has to be installed if the measuring and
(Figure 8.2.11) to a measuring transducer in the field is control cable can be influenced by lightning strikes to adjacent
mounted outside the building. Since the building is fitted with buildings, namely if the cable carries partial lightning currents.
an external lightning protection system, a type 1 lightning cur- If this can be excluded, type 2 surge protective devices are
rent arrester must be installed. Lightning current arresters or used (Figure 8.2.12).
combined arresters (type 1) of the BLITZDUCTOR XT family can
be used for this purpose. Case c
In case c, no measuring and control / telecommunications cable
Case b is installed outside the building. Although the building is fitted
Case b is similar to case a, however, the building in which the with an external lightning protection system, direct lightning
terminal device to be protected is located has no external light- currents cannot be injected into this part of the telecommuni-

Case a: external lightning protection system Case c: external lightning protection system

measuring
transducer

SPD
measuring and
control cable /
telecommunica-
tions cable
terminal device SPD terminal device

Figure 8.2.11 Building with external lightning protection system Figure 8.2.13 Building with external lightning protection system
and cables installed outside the building according to and cables installed inside the building according to
the lightning protection zone concept the lightning protection zone concept

Case b: Case d:

measuring
transducer

SPD
measuring and
control cable /
telecommunica-
tions cable
terminal device SPD terminal device

Figure 8.2.12 Building without external lightning protection system Figure 8.2.14 Building without external lightning protection system
and cables installed outside the building and cables installed inside the building

248 LIGHTNING PROTECTION GUIDE www.dehn-international.com