Surge arrestor

[sarves]

I want to know how do the rate of rise and the time to half value of a surge voltage determine the characteristics of a surge arresotr.Is it true 25kA(10/350us)is equal to 80kA(8/20us)? How to calculate these things?

 

[busbar]

For ANSI regions, possibly:

http://standards.ieee.org/reading/ieee/std_public/description/surge/C62.11-1993_desc.html

http://standards.ieee.org/reading/ieee/std_public/description/surge/