Contrary to SPDs for power supply systems, special attention has to be paid to
system compatibility and the operating characteristics of the measuring and control
or data line when installing SPDs in data processing systems. These protective
devices are connected in series with the data processing lines and must be able to
reduce the interference level below the immunity of the equipment to be protected.
Considering a single telephone line within the LPZs concept, the partial lightning
current on this conductor can be assumed to be a blanket 5 per cent. For lightning
protection systems class III/IV, this would amount to a partial lightning current of
5 kA, waveform 10/350 ms.
Figure 7.88 shows a lightning current arrester suitable for such specific
applications. It shows the approved multipurpose device BLITZDUCTOR CT, BCT
MOD BE as a lightning current and surge arrester. This protective device can be
used for protection of equipment in EMC LPZ I and higher. BLITZDUCTOR CT is
designed as a four-terminal network and limits both CM and DM interferences. It
can be fixed directly in the course of terminal blocks or, instead of these terminals,
on supporting rails, and its special design enables a space-saving arrangement.