Siemens SIMATIC NET PROFIBUS, Owner'S Manual, Page: 272 / 490

Installing LAN Cables
C-10
PROFIBUS Networks SIMATIC NET
6GK1970-5CA20-0AA1 Release 2 05/2000
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When removing the sheath of the cable, make sure that the braid shield of the
cables is not damaged.
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When selecting contact elements, remember that the cables for SIMATIC NET
PROFIBUS have a braid shield outer diameter of approximately 6 mm.
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To allow good contact between grounding elements, tin-plated or galvanically
stabilized surfaces are ideal. With galvanized surfaces, the necessary contact
should be achieved using suitable screws. Painted surfaces should be avoided
at the contact points.
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Do not use shield clamps/contacts for strain relief. The contact with the
shielding bar could be impaired or be broken altogether.
Figure C-4 Contacting the Shield at the Point of Entry to a Closet
C.4.4 Equipotential Bonding
When do potential differences occur?
Potential differences can, for example, be caused by different power supplies.
Potential differences between separate parts of the plant can be damaging for the
system in the following situations:
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Programmable controllers and peripheral devices are linked on grounded
connections
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Cable shields are contacted at both ends and grounded to different parts of the
plant.