Technical data

Installing bus cables
C.6 Electromagnetic compatibility of bus cables
PROFIBUS Network Manual
System Manual, Edition 04/2009, C79000-G8976-C124-03
265
Cable Shields
Note the following points about cable shields:
● Use SIMATIC NET PROFIBUS cables throughout your system. The shields of these
cables have an adequate shield density to meet the legal requirements regarding noise
emission and immunity.
● Always contact the shields of bus cables at both ends. The legal requirements for noise
emission and noise immunity in your system (CE marking) can only be achieved when
the shields make contact at both ends.
● Secure the shield of the bus cable to the connector casing.
● If cables are installed permanently, it is advisable to remove the insulation of the shielded
cable and to establish contact on the shield/PE conductor bar.
Note
If there is a potential difference between the grounding points, an illegally high
compensating current can flow through the shield grounded at both ends. To rectify the
problem, do not, under any circumstances, open the shield of the bus cable.
Install an additional bonding conductor parallel to the bus cable that takes over the shield
current (for notes on equipotential bonding refer to Section "
Equipotential bonding
(Page
267)") or use fiberoptic cable instead of electrical cable (safest solution).
Handling the shield
Note the following points when handling the shield:
● Secure the braided shield with metal cable clamps.
● The clamps must make good and largearea contact with the shield (see following figure).
● Contact SIMATIC NET PROFIBUS cables only using the braided copper shield and not
the aluminum foil shield. The foil shield is applied on one side to a plastic foil to increase
tearing strength and is therefore non-conductive.