Grounding, Shields, Polarity Section 4 Commissioning of PROFIBUS equipment
104 3BDS009029R5001 B
Grounding, Shields, Polarity
Always observe the following points when installing bus line grounding:
• Secure the shield braid using metal cable clamps.
• The clamps must fully enclose the shield and make good contact.
• Only connect the lines via the copper braid shield, and not via the aluminum
foil shield. One side of the foil shield is attached to a plastic film to increase its
tearing strength, and is therefore non-conductive!
• The shields of all cables which are routed into a cabinet from the outside must
be clamped at the point of entry inside the cabinet and connected to the cabinet
ground with a large contact surface area.
• When removing the cable jackets, it is important to ensure that the braid shield
of the cables is not damaged. Tin-plated or galvanically stabilized surfaces are
ideal for optimum contacting between grounding elements. With zinc-plated
surfaces, suitable threaded connections must be provided for the required
contacts. Painted surfaces at the contact points are unsuitable.
• Shield clamps/contact points should not be used as strain relief devices.
Contact with the shield bus could otherwise deteriorate or break completely.
Figure 38. Securing shielded lines using cable clamps and tube clips
(schematic diagram)
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