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Connecting up
5.4 Grounding
does not go first through the cable channel and then to the mounting plate or DIN rail terminal,
but goes directly to the mounting plate or DIN rail terminal.
The SCALANCE TAP has a terminal for grounding, refer to the section "Power supply (Page 32)".
The terminal is identified by the following symbol for the grounding.
1. Connect the terminal of the device with as short a cable as possible ≤ 150 mm and a large
cross-sectional area ≥ 2.5 mm² to the functional ground of the system. In many cases, the
entire metallic construction of the system serves as ground.
2. Also connect the standard rails of a system with ground.
Protective earth/functional ground
The connection of the reference potential surface with the protective earth system is normally
in the cabinet close to the power feed-in. This earth conducts fault currents to ground safely and
according to DIN/VDE 0100 is a protective earth to protect people, animals and property from too
high contact voltages.
Apart from the protective earth, there is functional grounding in the cabinet. According to
EN60204-1 (DIN/VDE 0113 T1) electrical circuits must be grounded. The chassis (0 V) is
grounded at one defined point. Here, once again the grounding is implemented with the lowest
leakage resistance to ground in the vicinity of the power feed-in.
With automation components, functional ground also ensures interference-free operation of a
controller. Via the functional ground, interference currents coupled in via the connecting cables
are discharged to ground.
In terms of the large-area and low impedance implementation, a functional ground set up for
this purpose generally also meets the requirements of protective earth. On the other hand,
protective earth does not always meet the requirements of functional ground. In general while
the connection for protective earth is always low resistance, it is not necessarily low impedance.
The resistance of a connection for protective earth must always be as small as possible to divert
fault currents safely to ground. The length of a protective earth cable can therefore be several
meters (m) long, without seriously impairing this effect. For a functional ground for diverting HF
disturbances, this cable does however have impedance and is therefore not suitable.
34
Operating Instructions, 06/2022, C79000-G8976-C447-03
SCALANCE TAP
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