Siemens SIMATIC ET 200AL System Manual page 27

Connecting
5.1 Rules and regulations for operation
Line voltage of the SELV/PELV power supply
The following section describes what you need to pay attention to with respect to the line
voltage (you will find additional information in the section Information on insulation, protection
class, degree of protection, and rated voltage (Page 90)):
● For stationary plants or systems without an all-pole line disconnector, there must be a
disconnector unit (all-pole) fitted in the building installation.
● For load current supplies, the configured rated voltage range must correspond to the local
line voltage.
● For all power circuits of the ET 200AL distributed I/O system, the fluctuation/deviation of
the line voltage from the rated value must be within the permitted tolerance.
24 V DC supply
Below there is a description of what you need to pay attention to with 24 V DC supply:
● For buildings:
If there is a danger due to overvoltages, you must take lightning protection measures for
external lightning protection (e.g. lighting protection elements).
● With 24 V DC supply lines and signal lines:
If there is a danger due to overvoltages, you must take lightning protection measures for
internal lightning protection (e.g. lightning protection elements. You will find additional
information in the Designing interference-free controllers
(https://support.industry.siemens.com/cs/ww/en/view/59193566) function manual).
● For 24 V DC supply:
Ensure that there is a safe (electrical) separation of low voltage (SELV/PELV) according
to IEC 61010-2-201 or IEC 60950-1.
You must secure all feeding supply voltages with a UL/IEC approved fuse 24 V DC/4 A
(trigger characteristic type B or C).
Protection against outside electrical influences
Below is a description of what you must pay attention to in terms of protection against
electrical impacts and/or faults:
● For all plants or systems in which the ET 200AL distributed I/O system is integrated, you
must ensure that the equipment or system is functionally grounded to discharge
electromagnetic interference.
● For supply, signal and bus cables, you must ensure that the cable routing and installation
is correct.
● For signal and bus cables, you must ensure that a wire/cable breakage or a cross-wire
does not lead to undefined states of the plant or system.
Reference
Additional information can be found in the function manual Designing interference-free
controllers (https://support.industry.siemens.com/cs/ww/en/view/59193566).
26
Distributed I/O system
System Manual, 08/2019, A5E31861578-AG