II - DCE FEL ČVUT v Praze

Mechanical Configuration of an Automation System with SIMATIC S7 Ex Modules
1.7.2 Wiring and Cabling in Cable Bedding Made of Metal or in Conduits
I/O Modules with Intrinsically-Safe Signals
C79000-G7076-C152-04
Cable bedding made of metal must be incorporated in the protective
measures to counteract indirect contact. This can be achieved by routing an
existing ground conductor made of steel strip or with a good conductive
connection between individual beds.
For single laying, conduits made of metal are now only usually used where
particular mechanical or thermal stress is developed. In general, PVC
conduits of two different types are used depending on the expected
mechanical stress. Remember, however, that PVC exhibits a linear expansion
which is about 8 times of that of metal. The fixing points must therefore be
such that the linear expansion is taken up.
1.7.3 Summary of Requirements of DIN VDE 0165/02.91
Table 1-1 Contents of DIN VDE 0165/02.91
The following table provides, once again, an overview of the most important
stipulations of DIN VDE 165/02.91 for cables and lines.
Application Requirements of cables and lines
General requirements:
Observe additional requirement for ”i”
and zone 0
(smaller cross section permissible for
multicore lines with more than 5 cores,
and lines for measurement and control,
for example)
Permissible types for portable/mobile
apparatus (does not apply to
intrinsically safe systems)
Select according to mechanical, chemical and
thermal influences
(refer to DIN VDE 0298 and DIN VDE 0891)
Protect against fire spread (e.g. lay cables in sand;
verify burning characteristics of lines in accordance
with VDE0472 Part 804, test type B)
Copper or aluminum conductor material (Al only for
multicore cables from 25 mm2 or single-core cables from
35 mm2 ; use suitable connection elements)
Minimum cross sections for copper conductor:
Single-core cable: 1 mm fine,
1.5 mm solid conductor
Multicore cable: 0.75 mm fine, otherwise as above
U