12v outside lights

[steve.t.]

hi.

Have to do a test on some 12v outside lights tomorrow to see if it's the lights that is tripping the rcd.
I'm confident in testing 230v but unsure how to go about it at 12v, could anyone explain how to go about this i want to do an insulation resistance test.
Any help would be great, thanks

 

[pushrod]

mains voltage parts tested at 500V, any adjacent mains lives and elv tested at 500V .
Elv lives tested at 250V . Remove lamps when testing.

Not sure that a fault on the elv side of a selv transformer is going to trip an rcd (mind it is late for me to be thinking lol)