Figure 5-2 Securing Shielded Cables With Cable Clamps And Cable Retainers - Siemens OLM/P11 V4.0 Operating Instructions Manual

Installation and Maintenance
5.1 Installation
Please note the following:
A minimum distance of 15 cm must be maintained between an OLM and a load
switching element (e.g. contactor, relay, temperature control, switch, etc.). This
minimum clearance is measured between the outside edges of the components
and must be adhered to in all directions around an OLM. The power supply lines
(24 V DC) of the OLM must not be laid in the same cable duct as power lines (load
circuits).
The lines +24 V DC and GND should be twisted with each other.
Recommendations on the arrangement of devices and lines with the aim of
achieving the lowest mutual influence possible can be found in EN 50174-2.
For applications in environments with heavy electromagnetic interference and for
use in shipbuilding, the retry value in the PROFIBUS master must be set to 4.
Bus cable shields.
Note the following measures for shielding lines:
- Use completely shielded SIMATIC NET PROFIBUS cables. The shields of these
cables have a density high enough to meet the legal requirements for disturbance
emission and immunity.
- Always connect the shields of bus cables at both ends. The legal requirements for
emissions and immunity can only be met by connecting the shield of the bus cables
at both ends (CE mark).
- Secure the shield of the bus cable to the connector housing or the cable clamps.
- In stationary use, it is advisable to strip the insulation of the shielded cable over
the entire length damaging it and to lay it on shielding/grounding rail.
Note:
If there are potential differences between the grounding points, an unduly high
compensating current may flow over the shield connected at both ends. Under no
circumstances disconnect the shield of the bus cable to solve the problem.
The following solution is permissible.
Install an extra equipotential bonding cable parallel to the bus cable and this can
then take up the shield current.
Shield connections
Securing shielded cables with cable
Figure 5-2
clamps and cable retainers
(schematic image)
28
Please note the following points when connecting
the cable shield:
Connect the shield braid with cable clamps
made of metal.
The clamps must surround the shield
making good contact over a large area
(see Figure 5-2).
Only contact the SIMATIC NET
PROFIBUS cables via the copper braid
shield and not via the aluminum foil shield.
The foil shield is applied to one side of a
plastic foil to increase the tensile strength
and therefore is not conductive!
The shielding of all cables entering a
switching cubicle from outside must make
large area contact with chassis ground.
The braid shield of the cables must not be
damaged when stripping the cable jacket.
Tin-plated or galvanically stabilized
SIMATIC NET PROFIBUS, Optical Link Module
Operating Instructions, 07/2008, A2B00065774O, Edition V1.5