Equipotential Bonding; Inductance Wiring - Emerson PACSystems RSTi-EP User Manual
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User Manual
GFK-2958J
CAUTION
•
If it is only possible to have a one-sided shield connection for reasons specific to the
circuit or equipment, the second side of the cable shield can be routed to the local
reference potential via a capacitor (with short connections). To prevent disruptive
discharges when interference pulses occur, a varistor or a resistor can also be wired in
parallel to the capacitor.
•
As an alternative, a doubled version (galvanically isolated) can be used, whereby the
inner shield is connected on one side and the outside shield is connected on both sides.
Equipotential Bonding
If system components are positioned separately from each other, potential differences may
arise, provided that:
•
•
A voltage equalizing cable must be used for equipotential bonding.
WARNING
The shield must not be used for equipotential bonding.
The following features are essential for a voltage equalizing cable:
•
•
•
•
•
Inductance Wiring
For inductive loads, it is recommended that protective circuits be placed directly on the
load. The earth (PE/FE) must be connected in a neutral-point configuration according to
regulations for switch cabinets.
Earthing and shielding
Power is provided from different sources
The earthing is implemented at different system parts, despite the cable shields
being connected at both sides
In the case of cable shields on both ends, the impedance of the equalizing cable must
be considerably smaller than that of the shield connection (maximum 10 % of its
impedance)
When the length of the equalizing cable is less than 200 m (656.2 ft), its cross-
section must be at least 16 mm2 (0.025 in2). If the cable is greater than 200 m
(656.2 ft) in length, a cross-section of at least 25 mm2 (0.039 in2) is necessary.
Large-surface connection with the PE conductor or the earthing and corrosion
protection are requirements for long-term safe operation
They must be made of copper or galvanized steel
In order to keep the enclosed area as small as possible, the equalizing cable and
signal cable must be routed as close to each other as possible
Chapter 7
Oct 2019
348
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