Original text - Engels - the conductor size actually selected is usually...

the conductor size actually selected is usually larger than that based on fusing because of factors such as
a. the conductor should have the strengh to withstand an expected mechanical and corrosive abuse during the design life of the grounding installation
b.the conductor should have a high enough conductance to prevent any possible dangerous voltage drop during a fault, for the life of the grounding installation
c.The need to limit the conductor temperature