This clause contains provisions for the application of voltage limitation to obtain an insulation coordination in the cases described in HD 60364-4-443, EN 60664-1, EN 62305-4 and CLC/TS 61643-12. SPDs, specific isolating transformers, filters or a combination of these may be used for protection against overvoltages. This clause gives the requirements for the selection and erection of: – surge protective devices (SPDs) for electrical installations of buildings to obtain a limitation of transient overvoltages of atmospheric origin transmitted via the supply distribution system and against switching overvoltages; – SPDs for the protection against transient overvoltages caused by direct lightning strokes or lightning strokes in the vicinity of buildings, protected by a lightning protection system. This clause does not take into account surge protective components which may be incorporated in the appliances connected to the installation. The presence of such components may modify the behaviour of the main surge protective device of the installation and may need an additional coordination. This clause also covers protection against overcurrent and consequences in case of SPD failure. This clause applies to a.c. power circuits. For d.c. power circuits, the requirements in this clause may be applied as far as is useful. For special applications, other or additional requirements may be necessary as specified in the relevant Part 7 of HD 60364.
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