Siemens Simatic S7-400

Wiring the S7-400
4-23
S7-400 and M7-400 Programmable Controllers, Installation Manual
C79000-G7076-C424-01
4.13 Interference-Free Configuration for Local and Remote
Connections
Use only Approved Components
Note
If you use components which are not approved for setting up local and remote
connections, interference rejection may be impaired.
Interference-Free Configuration for Local Connections
If you connect the CR and ER via suitable interface modules (send IM and receive
IM), no particular shielding and grounding need be implemented. Ensure, however,
that
 All racks have a low-impedance connection to each other
 The racks in a grounded arrangement have a star grounding configuration
 The contact springs of the racks are clean and not bent and will therefore
ensure the discharge of interference currents.
Interference-Free Configuration for Remote Connections
If you connect the CR and ER via suitable interface modules (send IM and receive
IM), normally no particular shielding and grounding need be implemented.
Special shielding and grounding may become necessary if you operate your
system in an environment with an extremely high level of interference. In that case,
observe the following points:
 In the cabinet, connect the cable shields to the shield bus immediately after
entry.
– Strip the outer cable insulation in the region of the shield bus without
damaging the braided shield.
– Ensure that the braided shield has the greatest possible contact area on the
shield bus, for example, with metal hose clamps surrounding the shield over
a large area.
 Connect the shield bus(es) over a large area to the frame or cabinet wall.
 Connect the shield bus(es) to the chassis ground.
In a remote connection, ensure that the VDE regulations for laying the protective
ground are not infringed.
Figure 4-9 shows the methods described here. If the permissible potential
difference between grounding points is exceeded, you must install an equipotential
bonding conductor (copper conductor with a cross-section of w 16 mm
2
).
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