Siemens 3VF Series Communications Manual page 99

Communication System Manual
Differences of potential
Note
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
2
1.5 mm
•
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
Version 1.0 (02/98)
.
2 .
© Copyright Siemens AG 1998. All rights reserved.
3WN1, 3WS1 Circuit-Breakers
99