7.3.3 Lightning equipotential bonding for IT systems

Lightning equipotential bonding for information technology installations as part of internal lightning protection is an expansion of protective equipotential bonding in accordance with IEC 60364-4-41 (Figure 7.3.1.1). In addition to the direct connection of all conductive parts in accordance with chapter 7.3.1 and the indirect connection of active conductors of the low-voltage installation in accordance with chapter 7.3.2, the supply lines of the telecommunications and signalling networks must also be included in the equipotential bonding. Due to the large number of different information technology systems, detailed knowledge of the electrical properties of information technology systems is required when selecting suitable protective measures, protective components and protective devices.  
The lightning current values listed in Table E.2 of IEC 62305-1 can be used to facilitate the selection of surge protective devices (SPDs) for lightning equipotential bonding of information technology systems. The lightning current discharge capacity derived from this for the calculation of SPDs as part of the lightning equipotential bonding is summarised in Table 7.3.3.1. The waveform of the lightning current (10/350 µs) indicates that SPDs must be used at this point that have a discharge capacity that complies with category D1 of product standard IEC 61643-21.