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British Standards relating to Lightning Protection

BS 6651:1999

BS 6651:1999, where it relates to the installation of lightning protection systems to new structures and new extensions to existing ones, was withdrawn on 31st August 2008. A lightning protection system commissioned or installed on a structure prior to this date should be maintained to BS 6651:1999, until such time that it is upgraded.

BS EN 62305

BS EN 62305 is the latest reference document for protection against lightning. It replaced BS 6651:1999 from 1st September 2008. It is the British edition of the European standard to which all lightning protection systems to new structures, and new extensions to existing ones, are now designed, installed and maintained. BS EN 62305 comprises four parts and these detail the fundamental requirements for lightning protection systems for the external and internal parts of a structure. The four parts are as follows:

  • Part 1: General principles
  • Part 2: Risk management
  • Part 3: Physical damage to structures and life hazard
  • Part 4: Electrical and electronic systems within buildings.

BS EN 62305-1 provides the general principles to be followed in the protection of structures against lightning, including their installations and contents as well as people.

BS EN 62305-2 is applicable to risk assessment for a structure due to lightning flashes. Its purpose is to provide a procedure for the evaluation of such a risk.

BS EN 62305-3 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 living beings due to touch and step voltages in the vicinity of an LPS.

BS EN 62305-4 provides information for the design, installation and maintenance of lightning electromagnetic impulse (LEMP) protection measures for electrical and electronic systems within structures, able to reduce the risk of permanent failures due to LEMP.

BS EN 62305 lightning protection systems comprise external (structural) and internal (surge protection etc.) components, where previous standards did not. It is now recognised that the electromagnetic effects of lightning related activity, and switching events, are the cause of much damage to systems and equipment, with the subsequent loss of critical data.

Surge protection devices (SPDs) were not required previously to comply with older standards. SPDs are required under BS EN 62305; they are part of the internal LPS and are installed firstly to prevent dangerous lightning currents from entering a building via its services, and secondly to reduce the risk of damage to electrical and electronic equipment and critical systems from transient over-voltages.


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