i am an self employed electrician and have a quick question im stumped on...i've just changed an old re-wireable fuse board for a new wylex split load duel rcd consumer unit, and whilst working on the new installation found that after i isolated the circuit wich im working on, when i cut through a piece of 2.5 mm twin wich was spurred off the ring main, the rcd DIDNT trip, i know that an rcd usually trips wether there is a load on the circuit or not when a nuetral to earth fault occurs. so i bridged the cable nuetral to earth (still isolated of course) and it still didnt trip. any one shed some light on this please i think that maybe because its an tnc-s system where the earth and nuetral are combined by PME and that there was no load on said circuit that that is why it didnt trip ??? and is this the case for any other earthing system ie tn-s tt etc