Siemens 8DJH Series Installation And Operating Instructions Manual page 69

Installation
These measures basically enable proper operation of the switchgear itself. The planner
or operator of the switchgear must decide whether additional measures are required
depending on the electromagnetic environment where the switchgear is installed.
Such measures must be implemented by the installation company in charge.
In an environment with heavy electromagnetic interference it may be necessary to use
shielded cables and wires for the external connections in order to avoid interferences in
the low-voltage compartment and thus, undesired influences on the electronic
protection and control or other automation devices.
Cable shields must be electrically bonded to be able to carry high frequencies,
and contacted concentrically at the cable ends.
The shields of cables and wires are connected and earthed in the low-voltage
compartment.
Connect the shields to earth potential - with high electrical conductivity and all around as
far as possible. Protect the contact surfaces from corrosion in case of humidity
(regular condensation).
When laying cables into the switchgear assembly, separate the control, signaling and
data cables and other lines with different signal and voltage levels by laying them on
separate racks or riser cable routes.
Corresponding to the different shield designs, there is a number of methods to perform
connection. The planning department or site management determines which of
the methods will be used, taking EMC requirements into account. The preceding points
should always be taken into account.
The shield is connected to cables or wires with clamps contacting all around.
If low demands are placed on EMC, it is also possible to connect the shield directly to
earth potential (combine or twist the shield wires) or via short cable connections.
Use cable lugs or wire-end ferrules at the connecting points.
Always keep the connecting leads of the shields as short as possible (< 10 cm).
If shields are used as protective earth conductors at the same time, the connected
plastic-insulated lead must be marked green/yellow over its entire length. Non-insulated
connections are inadmissible.
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