8 Guidelines for electrical installation
8.5 Potential compensation
XI/ON: XNE-GWBR-2ETH-IP
09/2011 MN05002007Z-EN
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8.5
Potential compensation
Potential differences can occur between installation components that are in separate areas
and these
• are fed by different supplies,
• have double-sided conductor shields which are grounded on different installation compo-
nents.
A potential-compensation cable must be routed to the potential compensation.
A potential compensation cable must have the following characteristics:
• Low impedance. In the case of compensation cables that are routed on both sides, the
compensation line impedance must be considerably smaller than that of the shield connec-
tion (max. 10 % of shield connection impedance).
• Should the length of the compensation cable be less than 200 m, then its cross-section
must be at least 16 mm
2
/ 0.025 inch
2
. If the cable length is greater than 200 m, then a
cross-section of at least 25 mm
2
/ 0.039 inch
2
is required.
• The compensation cable must be made of copper or zinc coated steel.
• The compensation cable must be connected to the protective conductor over a large
surface area and must be protected against corrosion.
• Compensation cables and data cables should be routed as close together as possible,
meaning the enclosed area should be kept as small as possible.
8.5.1
Switching inductive loads
In the case of inductive loads, a protective circuit on the load is recommended.
8.5.2
Protection against Electrostatic Discharge (ESD)
Warning
Never use the shield as a potential compensation.
Attention
Electronic modules and base modules are at risk from electrostatic discharge when
disassembled. Avoid touching the bus connections with bare fingers as this can lead
to ESD damage.
