Operation On Grounded Infeed - Siemens Simatic S7-1500R System Manual

Wiring

5.2 Operation on grounded infeed

Reference
Additional information can be found in the function manual, Designing interference-free
controllers (http://support.automation.siemens.com/WW/view/en/59193566).
5.2 Operation on grounded infeed
Introduction
Information is provided below on the overall configuration of an S7-1500R/H redundant
system on a grounded incoming supply (TN-S network). The specific subjects discussed are:
● Shut-off devices, short circuit and overload protection in accordance with
– IEC 60364, corresponds to DIN VDE 0100
– IEC 60204, corresponds to DIN VDE 0113
● Load current supplies and load circuits
Grounded infeed
In the case of grounding incoming supplies (TN-S system) the neutral conductor (N) and the
protective conductor (PE) are each grounded. Both wires form a part of the overvoltage
concept. When a plant is in operation, the current flows across the neutral conductor. When
a fault occurs, for example a single ground fault between a live conductor and ground, the
current flows through the protective conductor.
Safe electrical isolation (SELV in accordance with IEC 61131-2 or IEC 61010-2-201)
Load power supplies/system power supplies with a 24 V DC output voltage require safe
electrical isolation and a voltage limit (extra low voltage). Load power supplies/system power
supplies with a 24 V DC output voltage are not connected to the protective conductor.
In accordance with IEC 61131-2 / IEC 61010-2-201, this protection is referred to as SELV
(Safety Extra Low Voltage).
Either the wiring of SELV circuits must be isolated from the wiring of other circuits that are
not SELV, or the insulation of all wires must be dimensioned for the higher voltage.
Protective extra-low voltage (PELV in accordance with IEC 61131-2 or IEC 61010-2-201)
Load power supplies/system power supplies with a protective 24 V DC output voltage require
a safe connection to the protective conductor and a voltage limit (extra low voltage). In
accordance with IEC 61131-2 / IEC 61010-2-201, this protection is referred to as PELV
(Protective Extra Low Voltage).
Either the wiring of PELV circuits must be isolated from the wiring of other circuits that are
not PELV, or the insulation of all wires must be dimensioned for the higher voltage.
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S7-1500R/H redundant system
System Manual, 10/2018, A5E41814787-AA