Siemens PLT130
.
1994

4/16

Overvoltage protection
Description
Fig.4/23 Coar se overvoltage protection 6DS9 208-8AA
Application
The coarse and fine overvoltage protect ion components largely
protect the participants connected to the CS 275 bus from de-
struction as a result of ov ervoltages which result from i nterfer-
ences in the remote bus cable. The divis ion into coarse and fine
protection means that it is pos sible to optimally match the over -
voltageprotectionto the respective system.
The coarse protection limits power ful, high-voltage pulses t o the
arc voltage. It can briefly handl e currents in the kA range.
The fine protection reduces the residual vol tage between the
internal conductor and screen which pass es the coarse protec-
tion to a measure which is non--hazardous for the amplif ier of the
inductive coupler in the bus conver ter Ul.
The use of overvoltage protection component s is not mandatory
for operationof the CS 275 remotebus in non-disturbed system
environments. But their use is recommended if the effect of
overvoltages onto remote bus cables cannot be excluded.
Important notes:
The coarse and fine protection components do not replace a
lightningprotectionsystem installed according to the regula-
tions.
In conjunction with the so-call ed primary lightning protecti on
(connection and earthing of steel ar moring, equipotential bond-
ing etc.) you can reduce the extent of damage t o the bus partic-
ipants as a result of a lightning stroke, but thi s does not provide
complete protection from the damage of lightni ng.
Fig.4/24 Fine over voltage protection 6DS9 210-8AA
Design
Coarse protection
The coarse overvoltage protection 6DS9 208 -8AA is fitted in a
cast aluminum housing with degree of protect ion IP 54 and di-
mensions (lxwxh) 125 mm x 80 mm x 58 mm. I t contains 2
lightning arresters.
It is connected via an M5 threaded bolt t o the earthing system.
The screens of the remote bus cables which are combi ned in
the housing of the coarse protection can be connected if re-
quiredto the earthing systemeither directly or via oneof the two
lightning arresters (fl oating design).
The coarse protection is suitable f or all types of remote bus
cables.
Fine protection
The fine overvoltage protection bas ically consists of two Z
diodes and a terminator for t he remote cable which can be con-
nected when needed via the connecting splicing pl ate on the
connector board AF instead of the resistor present there. These
components are located on a miniature PCB which can be fitt ed
in the connector board 6DS9 203-8CA or --8DA.
The coarse and fine protection components can als o be retro-
fittedin existing system.
For configuring notes and ordering data s ee page 4/17.
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This catalog is out of date, see note on page 2