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Lightning Protection for buildings

Lightning Protection for buildings

Lightning Protection for buildings

(OP)
Hello,
I would like some information on lighting protection for a building.
IEEE 998 established lightning protection for substations
NFPA780 is a standard for installing lightning protection for various structures.

The building I am protecting is a GIS inside of a substation; due to the size of the substation the lightning
protection provided by the rest of the substation is not adequate enough to protect the building.

I am looking at the NFPA to use 18 inch terminating rods on the roof of the building to provide
a zone of protection. NFPA and IEEE uses different equations for the rolling sphere calculations. Although the
IEEE mentions the same equation as NFPA "S=10*I^(0.65)" is does not use this equation in annex B in the sample calculation.

How do I determine the strike distance for a building?
NFPA does not give a basis on what or how to solve for peak current. IEEE on the other hand has an equation I=2.2*(BIL)/Zs


NFPA uses a 10 kA current which leads to a strike distance of 150 ft, (section B.3.2.2)
Figure 2-3 in IEEE shows a curve of strike distance VS stoke current by checking 10 kA it seems the strike distance should be 120 ft.


Which should I use as the peak current? Once I know what the peak current is I can solve for the strike distance.


Your inputs are appreciated.
Thank you.

RE: Lightning Protection for buildings

It's not exactly my speciality, but the peak strike current might be a function of location. E.g. Florida.

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