the losses are too great, certain transmission
standards will longer complied with. the two systems are
connected via the shield, the equalising currents at-
tempt eliminate the potential difference.5 Transmission characteristics
Due their sensitive signal levels, data cables are
particularly susceptible interference. TN-C net-
works, severe interference can also occur the data
cable.TBS
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Cable shields minimise interference conducting
away the currents from the parasitic capacitances.
If the shield impacted lightning, the gas-dis-
charge protector ignites. This can lead
to connection errors complete interruption the
signal.1. The larger
the difference potential, the greater the equalising
currents. the current too great and the shield can-
not withstand it, cable fires can occur.
Device 1
Device 2
Data cable
Direct connection earth
Indirect connection earth
Gas-discharge table
Equipotential busbar
Earthing cable
Indirect earth one side
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229
Chapter The internal lightning protection system
.
Data cable with indirect earth one side
One way avoiding equalising currents earthing
the shield indirectly one end. case interventions the cable, for ex-
ample the integration connection sockets, plugs
and adapters, even the bending radius too
small, can safely assumed that signal losses will
occur.
Equalising currents are, however, still able flow
through the shield. This done con-
necting the shield the equipotential bonding via a
gas-discharge protector. This en-
sures that the shield not exposed the full current
at just one end.
3.3. The high impedance one end prevents
equalising currents from flowing. The connection the other
end has low resistance, leads directly the
equipotential bonding, the lightning current or
surge voltage can arrested both ends. The integ-
ration surge protection devices also counts an
intervention the cable. This happens when the earth res-
istance different different earthing systems, thus
creating potential difference. Because the gas-discharge
protector has resistance several gigaohms, there
is direct connection between the individual earthing
systems
