S 1.39 Prevention of transient currents on shielding

Initiation responsibility: Head of IT section

Implementation responsibility: Site/Bldg Technical Service; physical network operator

There are various ways of preventing transient currents on the shielding of data lines in buildings:

Transient currents can be avoided in the TN-C network by only linking IT appliances via shielded data lines which are connected to a common electrical distribution system. This must be checked each time the data network is extended.

In the event that this is not possible, transient currents can be avoided by only providing shielding on one side of the data line. In case of alteration to the data network, only suitable cables should be used (cables with shielding only on one side).

The optimum and safest method is to design the power distribution network in the entire building as a TN-S network. Here, the PE line and the N line are fed separately after the potential equalisation bar (PEB). Individual safeguards on IT equipment are then generally not necessary. Chapter S 1.28 Local uninterruptable power supply should be observed, however, regarding the creation of a new TN-S network for the connected equipment.

The following diagrams show the formation of transient currents on shielding and the possible safeguards:

Additional controls:

• Which type of network is in place?

• How are the protection conditions (a common distribution system or only single-sided shielding) checked and by whom?

• Are alterations to the data network co-ordinated with the site/building technical service?