User`s manual

Electromagnetic Compatibility Measures for Bus Adapter 170 INT 110 03
45
Overvoltage Protection for Remote Bus Lines (Lightning protection)
Overvoltage
protection
To protect the transmission equipment from coupled voltage spikes (lightning
strike), overvoltage protection equipment should be used in the remote bus cables,
as soon as it is laid outside of buildings.
The nominal discharge current should, in this case, be at least 5kA.
The lightning arrestors Type VT RS485 and Type CT B110 from Dehn und Söhne
GmbH & Co KG can, for example, be used. For the supplier address and order
numbers for protection equipment and accessories, see Overview of Ordering
Information, p. 50.
To protect an INTERBUS cable, two protection device groups are required in each
building. The first group (Type B110) is positioned where the cable enters the
building and is used as the lightning conductor. The second group (Type RS485),
close to the first node, is the overvoltage protection device.
Connection rules
for protection
devices
Before connection of the protection devices please observe the following rules:
Install a functional ground (equipotential bonding rail)
Assemble the protection devices near the building ground, so that the overload
current is diverted along the shortest route.
The cable(minimum 6mm
2
) to the building and functional ground should be as
short as possible.
A maximum of 10 protection devices connected in series with 4 open land
sections, for connecting buildings to each other, are allowed in the INTERBUS
cables.
Perform a Shield grounding (See Shield grounding with protection devices, p. 47)
of the INTERBUS lead according to the lightning arrestor used (type CT B110 or
type VT RS485).