Siemens SIMATIC S7-1500 System Manual page 61

Wiring
6.1 Rules and regulations for operation
24 VDC supply
The following describes what you must pay attention to in terms of the 24 VDC supply:
● Power supply units for the 24 VDC supply must have a safe electrical isolation in
accordance with IEC 60364-4-41.
● Overvoltage arresters are to be used as protection against lightning and overvoltages.
Suitable components for the lightning and overvoltage protection are specified in the
Defining interference-free controllers
(http://support.automation.siemens.com/WW/view/en/59193566) function manual.
Protection against electrical shock
The mounting rail of the S7-1500 automation system has to be connected conductively with
the protective conductor as protection against electrical shock.
Protection against external electrical influences
The following describes what you must pay attention to in terms of protection against
electrical influences and/or faults:
● For all plants or systems in which an S7-1500 CPU is integrated, you must ensure that
the plant or the system is connected to a protective conductor with sufficient cross-
section for conducting electromagnetic disturbances.
● For supply, signal and bus lines, you must ensure that the laying of the lines and the
installation is correct.
● For signal and bus lines, 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 (http://support.automation.siemens.com/WW/view/en/59193566).
60
S7-1500 Automation System
System Manual, 02/2014, A5E03461182-AB