Yup, you're both right. Mp is the center point conductor (center point = star point), Schutzleiter simply means protectiion conductor = PE.
Something real funny about German terminology though... "Schutzerde" used to be a real common term for PE. Nowadays German sparkies (and our Austrian teacher s as well) insist on the use of "PE" or "Schutzleiter" because in their opinion the old term isn't correct - it's referring to earth and in a TN-C-S system the PE isn't necessarily locally grounded so they want to avoid confusion by only using the term PE... whcih unfortunately stands for Protective Earth, meaning _word by word_ exactly the same as the German "Schutzerde"... those harmonization preachers don't seem to notice that!
