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Distance between other electrical systems

Former Community Member
Former Community Member
Hi all,


I've been asked this time and time again and it could be a case that I've looked at this so much that it's made me go insane, but I'd like a 2nd opinion.


When installing a TT feeder pillar on the street, does the 2.5m rule come into effect when it's located near to a PME system or does this need to be 2.5m away from all other systems which are not connected to the same earthing system (not connected to the earth mat/rod under the feeder pillar?  


My personal opinion is that they should be 2.5m away from anything that isn't on the same electrical installation (even if it's another TT system nearby) as if there's a fault with one and the path to earth is broken then the path would flow directly between the person or whatever touches it and take the route of least resistance. I have my copies of the 18th edition and the CoP for EVCEI, but I've been looking at it for so long it's made things become less clear the more questions I'm being asked about the regs!


Any help would be much appreciated,


Regards,


S
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  • 0
    further to that comment

    Exposed-conductive-parts of a TT system are at the potential of the TT system main earth terminal (which is hopefully the potential of the earth electrode).




    I'd respectfully suggest that

    Exposed-conductive-parts of a TT system should be at the or near the potential of the terra firma earth, that is to say the stuff you may stand on, whcih is a potential aquired by connection to the electrode. If the ground voltage is bouncing up and down because of a fault on a PME network nearby, ideally you would want all CPCs and  earthed metal work to bounce up and down with it, in the same way that a fence post will.


    I see nothing special about the electrode of a TT system, it's purpose in this context is to make sure that metal objects are at the same potential as the (terra firma) ground they stand on.

    Its other purpose is to fire an RCD if there is a live to CPC fault.

     


Reply
  • 0
    further to that comment

    Exposed-conductive-parts of a TT system are at the potential of the TT system main earth terminal (which is hopefully the potential of the earth electrode).




    I'd respectfully suggest that

    Exposed-conductive-parts of a TT system should be at the or near the potential of the terra firma earth, that is to say the stuff you may stand on, whcih is a potential aquired by connection to the electrode. If the ground voltage is bouncing up and down because of a fault on a PME network nearby, ideally you would want all CPCs and  earthed metal work to bounce up and down with it, in the same way that a fence post will.


    I see nothing special about the electrode of a TT system, it's purpose in this context is to make sure that metal objects are at the same potential as the (terra firma) ground they stand on.

    Its other purpose is to fire an RCD if there is a live to CPC fault.

     


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