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Figure 6.3.3 EMC spring terminals for the protected and unprotected side of a BLITZDUCTOR XT for permanent low-impedance shield contact
with a shielded signal line; with snap-on insulating cap for indirect shield earthing, cable ties and insulating strips.

¨ Cables without additional metal elements tial lightning current of the cable divided by the number
¨ Cables with metal sheath (e.g. metal vapour barrier) and / or of single cores + 1 shield = partial lightning current per
metal supporting elements core
¨ Cables with metal sheath and additional lightning protec- ¨ If the shield is not connected at both ends, it must be
tion reinforcement treated as if it were not there: Partial lightning current of
the cable divided by the number of single cores = partial
The splitting of the partial lightning current between informa- lightning current per core
tion technology lines can be determined using the procedures If it is not possible to determine the exact core load, it is ad-
in Annex E of the IEC 62305-1 (EN 62305-1) standard. The indi- visable to use the threat parameters given in IEC 61643-22
vidual cables must be integrated in the equipotential bonding (CLS/TS 61643-22). Consequently, the maximum lightning cur-
system as follows: rent load per cable core for a telecommunications line is a cat-
a) Unshielded cables must be connected by SPDs which are egory D1 impulse of 2.5 kA (10/350 μs).
capable of carrying partial lightning currents. Partial light-
ning current of the cable divided by the number of single Of course not only the SPDs used (Figure 6.3.5) must be ca-
cores = partial lightning current per core. pable of withstanding the expected lightning current load, but
b) If the cable shield is capable of carrying lightning currents, also the discharge path to the equipotential bonding system.
the lightning current flows via the shield. However, capaci- This can be illustrated based on the example of a multi-core
tive / inductive interferences can reach the cores and make telecommunications line:
it necessary to use surge arresters. Requirements:
¨ The shield at both cable ends must be connected to the
main equipotential bonding system in such a way that it
can carry lightning currents (Figure 6.3.4).
¨ The lightning protection zone concept must be used
in both buildings where the cable ends and the active
cores must be connected in the same lightning protec-
tion zone (typically LPZ 1).
¨ If an unshielded cable is laid in a metal pipe, it must be
treated as if it were a cable with a lightning current car-
rying cable shield.
c) If the cable shield is not capable of carrying lightning cur-
rents, then:
¨ If the shield is connected at both ends, the procedure is Figure 6.3.4 Lightning current carrying shield connection system
the same as for a signal core in an unshielded cable. Par- (SAK)

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