Configuring
S7-300 Programmable Controller Hardware and Installation
A5E00105492-01
4-21
4.8.5 Grounding
Bonding
Low-resistance connections to ground reduce the risk of electric shock in case of a
short-circuit or system fault. Low-impedance connections (large surface, large-
surface contact) reduces the effects of interference on the system or the emission
of interference signals. Here, effective shielding of cables and devices is also a
significant contribution.
Warning
All protection class 1 devices, as well as all larger metal parts, must be connected
to protective ground. This is the only way to ensure that the system user is
protected from electrical shock. It also deflects interference which is emitted from
external power supply cables and signal cables to cables connected to I/O devices.
Measures for protective grounding
The table below shows an overview of the most important measures for protective
grounding.
Table 4-8 Measures for protective grounding
Device Measures
Cabinet/mounting
structure
Connection to central ground (e.g. equipotential bus line) via
cables with protective conductor quality
Module rack / profile rail Connection to central ground with cable of minimum cross-
section of 10 mm
2
, if the profile rails are not installed in the
cabinet and not interconnected with larger metallic parts.
Module None
I/O Device Grounding via Schuko plug
Sensors and actuators Grounding in accordance with regulations applying to the
system
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