Lightning protection guide by OBO

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Last revision 2020

Vydal: OBO BETTERMANN s. r. o. Autor: OBO BETTERMANN

Strana 229 z 288

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the losses are too great, certain transmission standards will longer complied with. TN-C net- works, severe interference can also occur the data cable. the two systems are connected via the shield, the equalising currents at- tempt eliminate the potential difference.3. 3. The connection the other end has low resistance, leads directly the equipotential bonding, the lightning current or surge voltage can arrested both ends. This happens when the earth res- istance different different earthing systems, thus creating potential difference. 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 TBS Blitzschutz-Leitfaden 2018 / en / 2020/01/10 14:42:40 14:42:40 (LLExport_02613) / 2020/01/10 14:42:54 14:42:54 229 Chapter The internal lightning protection system . If the shield impacted lightning, the gas-dis- charge protector ignites. Equalising currents are, however, still able flow through the shield.TBS Blitzschutz-Leitfaden 2018 / en / 2020/01/10 14:42:40 14:42:40 (LLExport_02613) / 2020/01/10 14:42:54 14:42:54 Cable shields minimise interference conducting away the currents from the parasitic capacitances. Data cable with indirect earth one side One way avoiding equalising currents earthing the shield indirectly one end.1.5 Transmission characteristics Due their sensitive signal levels, data cables are particularly susceptible interference. 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. Because the gas-discharge protector has resistance several gigaohms, there is direct connection between the individual earthing systems. The integ- ration surge protection devices also counts an intervention the cable. This done con- necting the shield the equipotential bonding via a gas-discharge protector. The larger the difference potential, the greater the equalising currents. This en- sures that the shield not exposed the full current at just one end. The high impedance one end prevents equalising currents from flowing. This can lead to connection errors complete interruption the signal