Is my theory about earthing correct?

Had a discussion with my colleagues at work today around the theory of removing all earthing. 

This is my question:

If I poke my finger into the live terminal of a 230v socket, the line current travels through me, through the floor (earth), back through the earth to the supply transformer (because the transformer star point is also tied down to the general mass of earth) the fault currents travel back into the transformer star point and hopefully the completed path is of low enough impedance to be able to blow or trip the protective device serving the socket I touched.

Now. If the transformer star point WAS NOT connected down to earth, there would NOT be a return path from the socket I've stuck my finger in, back into the star point of the transformer and I wouldn't be able to recieve a shock as there is no complete return path.

Is that correct or not?

So following on from that, my question is: why cant we just isolate all transformers from earth and remove the risk of a "line to earth" shock? After all, this is exactly why we use SELV transformers in bathrooms no???? 

Obviously you could still get a line to neutral shock, but that's got nothing to do with the question I'm asking here. 

Parents
  • I suppose that another way of putting this is why not put a whole (SP) installation on an isolating transformer and do away with CPCs?

    So let's imagine that the line in your toaster comes adrift and touches the casing, and the neutral in your kettle comes adrift and ditto. You pop in your slice of bread whilst turning on the kettle and you are toast.

  • But in that case you'd be creating a short circuit from phase to neutral which would blow/ trip the fuse or protective device would it not?

Reply
  • But in that case you'd be creating a short circuit from phase to neutral which would blow/ trip the fuse or protective device would it not?

Children
  • no nothing would blow - there would just be 230V between the two metal objects, and if you connect yourself between them, your body resistance of a few k ohms  looks like a small extra legitimate load, nothing trips. There is no CPC connecting the cases  remember.  The only time anything trips is when there is a near short between the cases of the two defective devices.

    Mike

  • Yes, good point, my bad.