Operating instructions

Guidelines for Installing Networked Automation Systems in Buildings
7-6
SIMATIC NET Twisted-Pair and Fiber-Optic Networks
C79000-G8976-C125-02
7.3.1 Measures to Counter Interference Voltages
Overview
Measures are often taken to suppress interference voltages when the control
system is already in operation and problems occur receiving signals. You can
normally reduce the investment necessary for later restructuring of the system by
remembering the following points when installing your automation system.
S Setup an equipotential bonding system including all inactive metal parts
S Include a power distribution system with non-current PE grounding conductor
(for example using the TN-S system)
S Include shielding devices and bus cables
S Position devices and route cables suitably
S Take special noise suppression measures
The list shows that installing an interference-free networked automation system
simply with the tools for bus cable installation is not adequate. Measures must
already be taken during the planning phase of a system or building to ensure
harmony between all the equipment that requires electrically conductive
connections. Such measures include metallic structures in the building, conduits
for supply installations (gas, water, ventilation), as well as the electrical power
supply.
Standards for the Installation of Noise-Free Information Technology Systems
Based on the points outlined above, the standards committees of the European
Union formulated European standards for satisfactory installation and satisfactory
operation of information technology cabling within the infrastructure of a building in
which a power distribution system is operated at an effective value less than AC
1000 V (EN 50174).
The term “information technology” cabling/system includes all devices and cables
that transmit or process information electronically. The resulting standards can
therefore also be applied to automation systems.
Adherence to the standards when installing communication cabling (EN 50174,
/12/, /13/, /14/ series) and the requirements for bonding (EN 50310, /21/) is
strongly recommended. There are currently no international standards to compare
with these European standards in terms of detail.
The standards for the design of communications cabling (EN 50098, EN 50173,
/11/ series) are intended for applications in an office environment but nevertheless
include useful information for industrial applications.