Siemens CS 275 manual Overvoltage protection, Coarse overvoltage protection 6DS9 208-8AA

This catalog is out of date, see note on page 2

Overvoltage protection

Description

Fig. 4/23 Coarse overvoltage protection 6DS9 208-8AA Fig. 4/24 Fine overvoltage protection 6DS9 210-8AA

Application

The coarse and fine overvoltage protection components largely protect the participants connected to the CS 275 bus from de- struction as a result of overvoltages which result from interfer- ences in the remote bus cable. The division into coarse and fine protection means that it is possible to optimally match the over- voltage protection to the respective system.

The coarse protection limits powerful, high-voltage pulses to the arc voltage. It can briefly handle currents in the kA range.

The fine protection reduces the residual voltage between the internal conductor and screen which passes the coarse protec- tion to a measure which is non--hazardous for the amplifier of the inductive coupler in the bus converter Ul.

The use of overvoltage protection components is not mandatory for operation of the CS 275 remote bus 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 lightning protection system installed according to the regula- tions.

In conjunction with the so-called primary lightning protection (connection and earthing of steel armoring, equipotential bond- ing etc.) you can reduce the extent of damage to the bus partic- ipants as a result of a lightning stroke, but this does not provide complete protection from the damage of lightning.

Design

Coarse protection

The coarse overvoltage protection 6DS9 208-8AA is fitted in a cast aluminum housing with degree of protection IP 54 and di- mensions (l x w x h) 125 mm x 80 mm x 58 mm. It contains 2 lightning arresters.

It is connected via an M5 threaded bolt to the earthing system. The screens of the remote bus cables which are combined in the housing of the coarse protection can be connected if re- quired to the earthing system either directly or via one of the two lightning arresters (floating design).

The coarse protection is suitable for all types of remote bus cables.

Fine protection

The fine overvoltage protection basically consists of two Z diodes and a terminator for the remote cable which can be con- nected when needed via the connecting splicing plate on the connector board AF instead of the resistor present there. These components are located on a miniature PCB which can be fitted in the connector board 6DS9 203-8CA or --8DA.

The coarse and fine protection components can also be retro- fitted in existing system.

For configuring notes and ordering data see page 4/17.

4/16 Siemens PLT 130 . 1994