Siemens SIMATIC S7-400 Hardware And Installation Manual page 264

Assembling and Installing Systems
Shielding and Grounding under Industrial Conditions
If the monitor and programmable controller are operated under harsh industrial
conditions, you must observe the following:
On the side of the programmable controller:
Connect the cable shields in the cabinet to the shield bus immediately after
cabinet entry. The following points are important:
– Strip the video cables without damaging the conductors.
– Secure the outer braided shield with the largest possible area to the shield
bus of the programmable controller (for example, with metal hose clamps
which surround the shield, or with cable clamps).
Provide large-area contact between the shield buses and the frame or cabinet
wall.
Connect the shield bus to the ground point of the cabinet.
On the side of the monitor:
Isolate the electronic ground and housing ground from each other. Proceed as
follows:
– Remove the jumper on the monitor to separate the two grounds.
– Fit touch protection to the video sockets, because when the grounds have
been separated, a dangerous touch voltage of more than 40 V may be
present at the sockets.
Caution
!
There is a risk of personal injury.
Dangerous touch voltages may be present at the video sockets of the monitor.
Fit suitable touch protection to the sockets.
Connect the ground clamp of the monitor to the chassis ground.
Connect the cable shields to the ground clamp of the monitor as follows:
Proceed as follows:
– Strip the outer cable insulation of the video cables in the region of the
ground clamp of the monitor, without damaging the braided shield.
– Secure the outer braided shield over a large area to the ground clamp of the
monitor.
Figure A-6 shows a simplified representation of shielding and grounding for monitor
and S7-400.
A-24
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S7-400 and M7-400 Programmable Controllers, Installation Manual
C79000-G7076-C424-01