Standards define location categories and exposure levels for transient overvoltage protectors. This is based on the fact that the likely owrst case transient overvoltages the protector must (a) survive and (b) protect against, depend upon where it's installed.

Mains power supplies
The American standard IEEE C62.41, and subsequently BS 6651, SS CP 33 and others, define three location categories for mains power protectors. This is because as a mains borne transient travels through a building, the amount of current it can source becomes smaller (due to the impedance of mains cables and current division).