6.1.3 Prerequisites for the safe operation of the device in a system
WARNING
Risk of injury and damage caused by electrical current!
As a result of equipotential bonding currents between the SICK device and other
grounded devices in the system, faulty grounding of the SICK device can give rise to the
following dangers and faults:
■
Dangerous voltages are applied to the metal housings
■
Devices will behave incorrectly or be destroyed
■
Cable shielding will be damaged by overheating and cause cable fires
Remedial measures
►
Only skilled electricians should be permitted to carry out work on the electrical
wiring.
►
Ensure that the ground potential is the same at all grounding points.
►
If the cable insulation is damaged, disconnect the voltage supply immediately and
have the damage repaired.
►
Where local conditions are unfavorable and therefore do not meet conditions for
a safe grounding method (same ground potential at all grounding points), take
measures in accordance with the following formats.
The device is connected to the peripheral devices (voltage supply, any local trigger
sensor(s), PLC) via shielded cables. The cable shield – for the data cable, for example –
rests against the metal housing of the SICK device. The device can either be grounded
through the cable shield or through one of the threaded mounting holes.
If the peripheral devices have metal housings and if the cable shields also lie on their
housings, it is assumed that all devices involved in the installation have the same
ground potential.
This is achieved by complying with the following conditions:
■
Mounting the devices on conductive metal surfaces
■
Correct grounding of the devices/metal surfaces in the system.
■
If necessary: low-impedance and current-carrying equipotential bonding between
areas with different ground potentials
If these conditions are not fulfilled, equipotential bonding currents can flow along with
the cable shielding between the devices due to differing ground potentials; this can
be dangerous. This is, for example, possible in cases where there are devices within a
widely distributed system covering several buildings.
Remedial measures
The most common solution to prevent equipotential bonding currents on cable shields
is to ensure low-impedance and current-carrying equipotential bonding. If this is not
possible, the following solution approaches serve as a suggestion.
NOTICE
We expressly advise against opening up the cable shields. This would mean that the
EMC limit values can no longer be complied with and that the safe operation of the
device data interfaces can no longer be guaranteed.
Measures for widely distributed system installations
On widely distributed system installations with correspondingly large potential differen‐
ces, the setting up of local islands and connecting them using commercially available
electro-optical signal isolators is recommended. This measure achieves a high degree
of resistance to electromagnetic interference.
6
ELECTRICAL INSTALLATION
32
O P E R A T I N G I N S T R U C T I O N S | PLOC2D 4.1 8020736/1K3Z/2023-06 | SICK
Subject to change without notice
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