Shielding Devices And Cables - Siemens 6GK1 901-1GB01 System Manual

Installing network components in cabinets
3.3 Guidelines for setting up networked automation systems in buildings
Figure 3-5 Fiberoptic links avoid shield currents in the TNCS network
3.3.6.3

Shielding devices and cables

Shielding cables
The high degree of noise immunity of SIMATIC NET twisted-pair copper networks is
achieved by the exclusive use of shielded twisted-pair cables. The highly symmetrical
twisted signal wires are surrounded by a combination of foil and braided mesh shields. The
shield makes large-area, conductive contact with the casing of the attached end device or
network component at both ends of the twisted-pair cable via the connector/outlet. The entire
communications electronics, consisting of transmitter and receiver chips as well as the signal
cables is protected from electromagnetic influence from the outside world by a closed
"cocoon" of electrically conductive device casing and cable shield.
Note
The values specified for noise emission and noise immunity in the technical specifications of
all SIMATIC NET Industrial Ethernet components assumes the use of shielded twisted-pair
cables.
As explained in the installation rules for the devices, the shields of the twisted-pair cables
must make good conductive contact with the device housings at both ends. This is ensured
by the SIMATIC NET connectors designed specially to match the devices.
If, on the other hand, the rules are ignored and unshielded cables are used or the shields do
not make contact with the casing at both ends, there is no longer any guarantee that the
technical data regarding noise emission and noise immunity will apply. In this case, the
operators of the system must take responsibility themselves for compliance with the legal
limit values for noise emission and noise immunity (CE mark)!
Handling bus cable shields
Note the following points about cable shields:
● Use SIMATIC NET twisted-pair cables throughout your system. The shields of these
● Always contact the shields of bus cables at both ends. The legal requirements for noise
● Secure the shield of the bus cable to the connector casing.
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cables have an adequate density to meet the legal requirements regarding noise
emission and immunity.
emission and noise immunity in your system (CE marking) can only be achieved when
the shields make contact at both ends.
Passive network components
System Manual, 02/2013, C79000-G8976-C282-01