Lug contact area for lightning and grounding connections

[Power0020]

I wonder if there are much to mention about the required lug contact area for grounding conductors into steel structures and down conductors to lightning protection systems.

10 times the copper required cross-section area seems like a rule of thumb for some utilities when using steel structures as part of the grounding system especially for CT and VT structures. Nothing is mentioned about the lugs tho.

In IEC world however, the IEC 62271-301 dimensioning the equipment terminals suggests a current density of about 0.33 A/sq.mm for copper joints, that can be a basis to get a lug area?

Any clues?

 

[7anoter4]

NFPA 780/2011 chptr.4.8 states:
If a metal structure [chimneys, vents or roofs] thickness it is 4.8 mm or more shall require only connection to the lightning protection system. The air terminals shall be mounted on bases having a minimum contact area of 1940mm2 (3 in.2).
6.6.4 All connectors and splicers shall make contact with the conductor for a distance not less than 38 mm (11⁄2 in.), measured parallel to the axis of the conductor.
If the fitting is constructed of a metal other than copper or aluminum the minimum cross-sectional area shall be:
A=3.8*10^9*SQRT(ρ/Cp/D/(MP-298)) mm^2
Where:
Ρ=material resistance [Ω.m]
Cp=specific heat capacity[J/kg/K]
D=density[kg/m^3]
MP=melting point[K]

 

[7anoter4]

I forgot to mention [referring to the metal structure connection to the lightning protection system]:
4.8.10.3.1 The connection shall be made to bare metal at the base or lower edges of the unit using main-size lightning conductors and bonding devices that have a surface contact area of not less than 1940 mm2 (3 in.2) and shall provide two or more paths to ground, as is required for strike termination devices.