How do detrmine the level of mechanical protection required, using the UK 16th regs

senario....
Install in a domestic garage one end, a work bench is fitted. So we know the T&E cabeling requires to be in conduit. But how do you decide if it should be plastic conduit or metal conduit?

Quote from 16th regs

522-06 Impact (AG)

522-06-02 In a fixed installation where an impact of medium severity (AG2) or high severity(AG3) can occur, protection shall be afforded by:
(i) the mechanical charicteristics of of the wiring system,or
(ii) the location selected,or
(iii) the provision of additional local or general mechanical protection,
or by any combination of the above.

So how do we determine the levels of severity, AG2 and AG3?


der Großvater