Technical data

Lightning and overvoltage protection of bus cables between buildings
B.2 Protecting bus cables from lightning
PROFIBUS Network Manual
254 System Manual, Edition 04/2009, C79000-G8976-C124-03
Bus cables between buildings
Since bus cables between buildings are subject to higher overvoltage risks (the effects of
lightning), the nodes included in the attached bus segment must be protected from the
effects of overvoltage.
Lightning protection facilities for bus cables are implemented in two different components,
coarse protection and fine protection.
Basic protection
While coarse protection prevents the progress of highenergy lightning currents at the point of
entry to the building, the fine protection installed in the vicinity of the DTE provides finer
limitation of overvoltage for the bus node.
● The lightning protection devices described below represent a protection concept
developed in conjunction with the company of Dehn & Söhne for SIMATIC NET
PROFIBUS and that can be used for all transmission rates (9.6 kbps to 12 Mbps). The
devices can be ordered directly from the firm of Dehn & Söhne; ordering data are listed
below.
● When configuring a network, remember that the coarse and fine protection together must
be considered as a node (reduction of the number of nodes in segments with lightning
protection modules).
● If a PROFIBUS segment runs through several buildings (several lightning components
used in series), a repeater should be installed in each building to refresh the signal.
AG
AG
Fine protection close to
first node
PLC
PLC
Underground cable,
Potential bonding conductor
Coarse protection at
entry to building
Same protective design
on other
cable inlet or
outlet necessary
Figure B-1 Lightning protection concept for bus cables between buildings