Siemens Simatic S7-400

Wiring the S7-400
4-15
Automation System S7-400 Hardware and Installation
A5E00850741-01
4.10 Interference-Free Configuration for Local and Remote
Connections
Use only Approved Components
Note
If you use components which are not approved for s etting up local and remote
connections, interference rejection may be impaired.
Interference-Free Configuration for Local Connections
If you c onnect the CR and ER via suitable interface modules (send IM and receive
IM), no particular s hielding and grounding need be implemented. Ensure, however,
that
• All r acks must have a low-impedance connection to each other
• The racks in a grounded arrangement must have a star grounding configuration
• The contact s prings 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 c onnect the CR and ER via suitable interface modules (send IM and receive
IM), normally no particular shielding and grounding need be implemented.
Special s hielding 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 a fter
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.