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Revision 04 * INSTALLATION AND OPERATING INSTRUCTIONS 8BT2 * 881-4027.9
• reliable earth connections of the frame parts via toothed contact washers or locking
washers;
• inside the panel, wires are laid in metal ducts;
• spatial separation of sensitive signal wires from wires with high interference voltage
levels;
• limitation of switching over voltages of inductive loads (e.g. relay or contactor coils,
motors) by means of protective circuits with diode, varistor or RC element;
• within the LV compartment, the secondary devices are mounted in defined zones;
• shortest possible connection between corresponding modules in sub-racks;
• consideration of the magnetic leakage fields of conductor bars and cables;
• protection of sub-racks and wiring backplanes against interference by perforated
shielding plates;
• large surface bonding between all modules and devices as well as bonding to the
earthing conductor of the switchgear assembly.
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.
2.1.8. Rating plates
The rating plates contain all relevant data for the cubicle and its components.
Rating plates are located:
• On the inside of the door of the low-voltage compartment (rating plates for
cubicle, current/voltage transformers)
• On the gear block of the circuit breaker (circuit breaker rating plate)
