There is an national-consensus standard that deals with switchgear modifications, but if it has not been referenced by engineering concerns or unfamiliar to the AHJ, there’s not much point using it, other than to relieve some liability of the organization performing the work. ANSI/IEEE Std C37.59-2002 …Requirements for Conversion of Power Switchgear Equipment [An earlier version is described at
http://standards.ieee.org/reading/ieee/std_public/description/switchgear/C37.59-1996_desc.html The 2002 edition is cataloged at http://shop.ieee.org/ieeestore/Product.aspx?product_no=SS95026]
