Rules and Guidelines
Want to participate in the discussions? Please read our Community Rules and Guidelines. Need some help? Visit Support and Answers.

  • State Not Answered
  • Locked Locked
  • Replies 19 replies
  • Subscribers 32 subscribers
  • Views 4984 views
  • Users 0 members are here
Options
You may also be interested in
This discussion is locked.
You cannot post a reply to this discussion. If you have a question start a new discussion

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
Parents
  • 0
    In practice, this is no sillier than a pair semi-detached cottages with TT supplies, each with a bond to a metal water main that effectively interconnects them. As such it is not especially dangerous, and may actually make things safer. However, I think the letter of BS7671 is that pairs of TT systems with different origins (and the origins would be the company fuses) are to be treated no different in terms of segregation rules to any other system, and the fact they share a substation is ignored.

    From first principles, I'm inclined to agree with you, as a credible fault that could make anything live for longer than an RCD tripping time is not likely; but the rules as currently written are against that interpretation.
Reply
  • 0
    In practice, this is no sillier than a pair semi-detached cottages with TT supplies, each with a bond to a metal water main that effectively interconnects them. As such it is not especially dangerous, and may actually make things safer. However, I think the letter of BS7671 is that pairs of TT systems with different origins (and the origins would be the company fuses) are to be treated no different in terms of segregation rules to any other system, and the fact they share a substation is ignored.

    From first principles, I'm inclined to agree with you, as a credible fault that could make anything live for longer than an RCD tripping time is not likely; but the rules as currently written are against that interpretation.
Children
No Data

Join us to get the best from IET EngX.

Joining EngX lets you personalise your experience so you stay up to date on the topics that interest you, plus you’ll be able to make connections who are looking to collaborate, exchange ideas and more.

Join us Not now

Community Rules & Guidelines