User manual

Earthingandshielding | Shielding of cables
251Manual u-remote1432790000/03/02.2014
ATTENTION
Material damage!
If it is only possible to have a one-sided shield connection
for reasons specic to the circuit or equipment, the second
side of the cable shield can be routed to the local reference
potential via a capacitor (with short connections). To pre-
vent disruptive discharges when interference pulses occur,
a varistor or a resistor can also be wired in parallel to the
capacitor.
As an alternative, a doubled version (galvanically isolated)
can be used, whereby the inner shield is connected on one
side and the outside shield is connected on both sides.
Equipotentialbonding
If system components are positioned separately from each
other, potential differences may arise, provided that:
– Power is provided from different sources
– The earthing is implemented at different system parts,
despite the cable shields being connected at both sides
A voltage equalising cable must be used for equipotential
bonding.
WARNING
Possible danger to life!
The shield must not be used for equipotential
bonding!
The following features are essential for a voltage equalising
cable:
– In the case of cable shields on both ends, the impedance
of the equalising cable must be considerably smaller than
that of the shield connection (maximum 10 % of its
impedance)
– When the length of the equalising cable is less than
200m, its cross-section must be at least 16 mm
2
If the
cable is greater than 200m in length, a cross-section of
at least 25 mm
2
is necessary.
– Large-surface connection with the PE conductor or the
earthing and corrosion protection are requirements for
long-term safe operation
– They must be made of copper or galvanised steel
– In order to keep the enclosed area as small as possible,
the equalising cable and signal cable must be routed as
close to each other as possible
Inductancewiring
For inductive loads, it is recommended that protective cir-
cuits be placed directly on the load. The earth (PE/FE) must
be connected in a neutral-point conguration according to
regulations for switch cabinets.
ATTENTION
Material damage due to electrical discharge!
When disassembled, u-remote modules and couplers are at
risk of ESD. Therefore, avoid touching bus connections with
bare hands, as this can lead to damage due to electrostatic
discharges.