Operating instructions

Guidelines for Installing Networked Automation Systems in Buildings
7-3
SIMATIC NET Twisted-Pair and Fiber-Optic Networks
C79000-G8976-C125-02
7.2 Protection from Electric Shock
Twisted-Pair Signal Level
The signal levels on twisted pair cables are low voltage. Correctly installed and
operated twisted pair bus cables do not have dangerous electrical voltages.
Nevertheless you should remember the following rules when installing the power
supply for all components (DTEs, bus components, etc.) that you want to connect
to twisted-pair cable.
Operation with 24 V DC
Numerous SIMATIC NET components require a voltage of 24 V DC as their
operating voltage or as auxiliary contact voltage. This power supply must meet the
requirements of an extra-low voltage with reliable electrical isolation from the main
power system, complying with IEC 60950 or EN 60950 /18/.
Operation with Live Voltage
Components operated with live voltage must meet the requirements for protection
against electric shock as stipulated in EN 60950 /18/, EN 61131-2 /20/, EN 61010
/19/ or other applicable product standards.
All the signals of the twisted-pair port must meet the requirements of reliable
electrical isolation from the main power supply, complying with IEC 60950 or EN
60950 /18/.
Cabling Components
Conductive cable path systems, barriers, and accessories must be included in the
protective measures preventing indirect contact (protection against illegal
dangerous contact voltage).
Grounding conductors (PE) and equipotential bonding conductors must be installed
according to the requirements of systems in buildings complying with HD 384.4.41
(protective measures against electric shock) and HD 384.5.54 (grounding and
grounding conductor). The application of EN 50174-2 is recommended for the
separation of low voltage cabling and IT cabling.
The requirements of HD 384.4.47 S2 (application of measures for protection
against electric shock) and HD 384.4.482 S1 (selection of protective measures as
a function of external influences) and appropriate national or local regulations must
be adhered to.