Wiring the S7-400
4-15
AutomationSystem S7-400 Hardwareand Installation
A5E00850741-01
4.10 Interference-Free Configuration for Local and RemoteConnections

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 must have a low-impedance connection to each other
•The racks in a grounded arrangement must have a star grounding configuration
•The contact springs of the racks must be clean and may not be 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. Inthat 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.