I have a 220m structure that requires a lightning protection system.
I am used to seeing 75mm2 or 120mm2 copper tape, but I want to find a way to justify the design.
ANSI/NFPA 780 gives me a minimum of 58mm2
IEC 61024-1 I think, but I’m not sure has a minimum requirement of 50mm2.
Can anyone guide me towards a comparison table of the various codes? Apart from reading directly from tables in the codes is there any calculation method for sizing of ten copper tape?
There’s also the issue of keeping the length-to-width ratio of the tape below some value. But I recall that this might be ‘recommended practice’ (as opposed to Code).
Length-to-width ratio is related to the inductance and thus the voltage rise. This consideration may be why wide Cu tapes are often used (?) for grounding conductors. It almost certainly doesn’t matter for lightning protection of structures, but the ratio could be a consideration for the grounding conductors used at the building entrance where the protection devices would be installed. I know that some trustworthy lightning protection vendors do sell very wide Cu straps.
I wouldn’t worry about it for basic structural lightning protection.
Above is a snippet.