the two systems are
connected via the shield, the equalising currents at-
tempt eliminate the potential difference. 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. This done con-
necting the shield the equipotential bonding via a
gas-discharge protector. Because the gas-discharge
protector has resistance several gigaohms, there
is direct connection between the individual earthing
systems. The connection the other
end has low resistance, leads directly the
equipotential bonding, the lightning current or
surge voltage can arrested both ends.3.
Equalising currents are, however, still able flow
through the shield. The high impedance one end prevents
equalising currents from flowing. This en-
sures that the shield not exposed the full current
at just one end.1. This happens when the earth res-
istance different different earthing systems, thus
creating potential difference. The larger
the difference potential, the greater the equalising
currents. TN-C net-
works, severe interference can also occur the data
cable. This can lead
to connection errors complete interruption the
signal. the losses are too great, certain transmission
standards will longer complied with.
3.
If the shield impacted lightning, the gas-dis-
charge protector ignites.5 Transmission characteristics
Due their sensitive signal levels, data cables are
particularly susceptible interference. The integ-
ration surge protection devices also counts an
intervention the cable.TBS
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Cable shields minimise interference conducting
away the currents from the parasitic capacitances. the current too great and the shield can-
not withstand it, cable fires can occur.
Data cable with indirect earth one side
One way avoiding equalising currents earthing
the shield indirectly one end.
Device 1
Device 2
Data cable
Direct connection earth
Indirect connection earth
Gas-discharge table
Equipotential busbar
Earthing cable
Indirect earth one side
TBS
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229
Chapter The internal lightning protection system
