MT 21 - TC 81/MT 21

IEC 62305-3:2024 provides the requirements for protection of a structure against physical damage by means of a lightning protection system (LPS), and for protection against injury to human beings due to touch and step voltages in the vicinity of an LPS (see IEC 62305-1).
This document is applicable to the:
a) design, installation, inspection and maintenance of an LPS for structures without limitation of their height,
b) establishment of measures for protection against injury to human beings primarily due to touch and step voltages.
This third edition cancels and replaces the second edition published in 2010. This edition constitutes a technical revision.
This edition includes the following significant technical changes with respect to the previous edition:
a) Minimum thicknesses of metal sheets or metal pipes are given in Table 4 for air-termination systems where it is necessary to prevent hot-spot problems. Maximum temperature rises ΔT (K) and time duration t50 (s) for different thicknesses and long strokes are also given.
b) Cross-reference to the IEC 62561 series is made for the use of reliable, stable, safe and appropriate LPS components.
c) The application of two methods – general and simplified – for separation distance calculation is clarified.
d) Some changes to the requirements for continuity of steel reinforcement are made.
e) Annex C is revised to address comments from IEC subcommittee 31J.
f) Revision of positioning of air-termination conductors are modified according to the three accepted methods. A more precise description of the methods for positioning of the air-termination systems are made according to the complexity of structures to be protected. The main text has been simplified, Annex A has been deleted and all detailed information has been moved to Annex D.
g) Information on the protection of green roofs is introduced in Annex D.
h) Information on the protection of protruding parts on facades of tall buildings is introduced in Annex D.
i) a new definition of “electrically insulated LPS” has been introduced to distinguish it from an LPS both electrically and physically isolated from the structure, with a slight modification of the other LPS definitions.