6.4.5.1 Conditions for an electrically insulated lightning protection system

With the publication of the October 2024 edition of IEC 62305-3, the term 'electrically insulated lightning protection system' was newly introduced and distinguished from the previous designation 'isolated lightning protection system'. This clarification of terminology serves to better distinguish between different types of external lightning protection systems and contributes to clarity in planning, implementation and testing.
An electrically insulated lightning protection system is characterised by the fact that there is no electrically conductive connection between the active lightning current paths (e.g. down conductors) and the electrically conductive parts of the structure to be protected. Except for the earthing system in the ground, an insulated lightning protection system has no electrical contact with the structure to be protected. The aim is to prevent uncontrolled sparkovers due to induction effects and potential differences when lightning current passes through.