This discussion is locked.
You cannot post a reply to this discussion. If you have a question start a new discussion

Minimum values of insulation resistance

What is the science behind the 1 MOhm minimum insulation resistance? What is the basis for this particular value?
Parents
  • I think those are 'potential' dangers. Diverted neutral currents flow up every water and gas pipe in some streets, without injury, as the DNOs do not distinguish between N and E, and in other parts of the world an NE bond would be permitted and in some cases required by regulation .

    Consider this little sketch of MEN wiring
    def624a26d54b2a5d2a02ea55ce7d6db-huge-men_wiring.png

    shamelessly pilfered from the   Q and A pages of the Australian National Electrical and Communications Association.   

    Here there is no CPC to the outbuildings 2 or 3, and an NE bond creates a local CPC.

    Personally I do not like it either, but equally they do not like our use of TT in that situation. However, if it was done that way here that does not make it immediately more dangerous then over there, just non-compliant with our regs, and, in the UK at least, illegal as well,  if you are a consumer of electricity and not a distributor. (But then plenty of UK sites with more than one LV transformer have an LV interconnection arrangement that in effect means more than one NE bond.)



Reply
  • I think those are 'potential' dangers. Diverted neutral currents flow up every water and gas pipe in some streets, without injury, as the DNOs do not distinguish between N and E, and in other parts of the world an NE bond would be permitted and in some cases required by regulation .

    Consider this little sketch of MEN wiring
    def624a26d54b2a5d2a02ea55ce7d6db-huge-men_wiring.png

    shamelessly pilfered from the   Q and A pages of the Australian National Electrical and Communications Association.   

    Here there is no CPC to the outbuildings 2 or 3, and an NE bond creates a local CPC.

    Personally I do not like it either, but equally they do not like our use of TT in that situation. However, if it was done that way here that does not make it immediately more dangerous then over there, just non-compliant with our regs, and, in the UK at least, illegal as well,  if you are a consumer of electricity and not a distributor. (But then plenty of UK sites with more than one LV transformer have an LV interconnection arrangement that in effect means more than one NE bond.)



Children
No Data