Communication System Manual 3WN1, 3WS1 Circuit-Breakers
Version 1.0 (02/98) Copyright Siemens AG 1998. All rights reserved. 99
Note
Differences of potential
!
If there are differences of potential between the earthing points, compensating
current can flow across the screen connected at both ends. Install an additional
equipotential bonding conductor in this case.
Please note the following items with regard to the screen:
• Use metal cable clamps for fixing the braided screens. There must be a good, large-area
contact between the clamps and the screen.
• Connect the screen to a screen bus immediately after the cable enters the cubicle. Run the
screen through as far as the module but do not connect it again!
Fig. 21: Possible cable screen connections
Screened data cables and unscreened power supply cables (< 60 V DC) are run through to the
interface module and connected. All the cable screens must be earthed at both ends in order to
comply with EMC limits.
• The PROFIBUS-DP cable screen must be connected to the equipotential bonding strip as it
enters the switchgear cubicle.
• The supplied screened 3WN1 connecting cable must be earthed on the shield terminal of
the interface module using a flexible wire (as short as possible) with a cross-section of
1.5 mm
2
.
• The other end of the screen on the 3WN1 connecting cable must be earthed on the SUB-D
connector of the circuit-breaker using a flexible wire (as short as possible) with a cross-
section ≥≥ 2.5 mm
2
.
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