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Initiation responsibility: Head of Site Technical Services
Implementation responsibility: Site Technical Services
The direct impact of a lightning strike on a building (damage to structural elements, roof truss fire etc.) can be prevented by installing a lightning arrester that complies with the DIN/VDE 0185 standard. Besides this outside lightning protection it is virtually essential to provide internal lightning protection in the form of overvoltage protection. This is required because the lightning arrester does not protect electrical equipment contained inside the building. This can only be achieved by overvoltage protection (cf. S 1.25 Overvoltage protection), the high costs of which must be justified in relation to the items to be protected.
For full protection against lightning it is necessary for all the safety devices to refer to the same base potential. External lightning protection is connected with the potential equalisation bar (PEB) in accordance with the requirements of DIN VDE 0185 "Lightning Protection Systems". This for its part is connected with the PEN or N and PE conductors of the electrical installation in the building. During a flash of lightning a voltage that is proportional to the current is generated at the ground potential of the lightning protection system. The potential of the PEB and hence of the N and PE conductors in the building increases and can reach values of several 10,000s of volts. Voltages are reached between N and PE conductors and conductors L1/L2/L3 which significantly exceed the normal levels of 230/400V. Damage can occur to equipment and cables. Transient currents between data and power supply networks, for example due to inadequate shielding, can result in the destruction of IT equipment (on this point see S 1.39 Prevention of transient currents on shielding). Because of the possibility of parallel runs it is just as important to consider all networks (building services management systems, wide area networks) with regard to cross-talk as to include external cables that run into the building (see also S 1.5 Galvanic separation of external lines).
Example
As a result of a lightning strike, EUR 10,000 of damage was caused to IT equipment (PCs, servers, laser printers) in the southern German branch of a service company. As a result, the building was furnished with external lightning protection without internal lightning protection (overvoltage protection). A second lightning strike led to a similar amount of damage the new external lightning protection.
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by Bundesamt für Sicherheit in der Informationstechnik |
July 2001 |