If lightning strikes and the lightning current flows into
an air-termination rod and earth via the external
lightning protection system, approximately 50% the
lightning current enters the building via the building’s
equipotential bonding system and hence couples gal-
vanically. the case light-
ning strike, passes into the cable directly, this is
known galvanic coupling.External lightning protection
system
Earthing system
Main earthing busbar
Transmitter
Data cable carrying lightning
current
Galvanic coupling into data cable via the external lightning protection system
"Galvanic coupling"
When lightning current, e. metal rodent guard can turn even
an EMC-insensitive fibre optic cable into conductor
of lightning current.g.
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Chapter The internal lightning protection system
.
Coupled lightning currents are not always due the
external lightning protection system: principle, any
external cable that ends the house can couple light-
ning currents, for example, strike substation or
an exposed cable connected the house. Lightning
current can also enter the building via the telecommu-
nications cable
