14:25 Feb 10 

I had thought that "masse" and "terre" were interchangeable, but a lengthy document concerning this very issue has convinced me otherwise. "Earth" potential is conventionally zero, but the potential of a "masse" (ie the structural elements of a building or piece of electrical machinery) is not necessarily the same as "earth", and can even vary from one part of the masse to another.
I'm confused by "conduite": either this is a typo for "conduit" or the author is referring to the abstract "conduction" of electricity, which would be an odd use of "conduite".