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 4 replies
  • Subscribers 32 subscribers
  • Views 1976 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

Multiple Earth Electrodes TT System

Steve UKBC
Thoughts or suggestions welcome....


Is there any issue or downside to having multiple earth electrodes installed on a single TT system (all areas have there CPC connected together) when the TT system spans a large area (we are taking about a 400m x 400m area)?


For example


If you had a couple of farm barns/sheds (metal framed) close together with multiple earth electrodes and some few hundred meters away you have a camp site with multiple earth electrodes (one at each power outlet etc) and then connect the CPC from the barns to the camp site to make one large TT system?



Parents
  • 0
    AJJewsbury:

    In general multiple electrodes would be considered a good thing - as generally a lower overall Zs and likely more reliable too.


    The only flipside I can think of is that having one large TT system rather than several small ones is that the rise PE potential during a L-PE fault will affect a larger area. Normally that's not too much of a concern but could be significant, say if an RCD was faulty and so failed to disconnect at all.


       - Andy.


    Would you suggest using 2 rather than one RCD just after the DNO cutout (identical RCD's different manufactures) could be a way forward to protect against this or would this just be over engineering, considering the size of installation?


    I suggested two identical RCDs in one place due to the possibility of both tripping on a earth fault and it being easier or more convenient to reset both RCDs in one location. Note that the plan is to have a time delayed RCD after the DNO and final circuits using RCBO's and would not want to go down the route of a adjustable RCD to provide selectivity if a 3rd RCD device was to make its way into the circuit.


    hope i made sense 


    Steve


     


Reply
  • 0
    AJJewsbury:

    In general multiple electrodes would be considered a good thing - as generally a lower overall Zs and likely more reliable too.


    The only flipside I can think of is that having one large TT system rather than several small ones is that the rise PE potential during a L-PE fault will affect a larger area. Normally that's not too much of a concern but could be significant, say if an RCD was faulty and so failed to disconnect at all.


       - Andy.


    Would you suggest using 2 rather than one RCD just after the DNO cutout (identical RCD's different manufactures) could be a way forward to protect against this or would this just be over engineering, considering the size of installation?


    I suggested two identical RCDs in one place due to the possibility of both tripping on a earth fault and it being easier or more convenient to reset both RCDs in one location. Note that the plan is to have a time delayed RCD after the DNO and final circuits using RCBO's and would not want to go down the route of a adjustable RCD to provide selectivity if a 3rd RCD device was to make its way into the circuit.


    hope i made sense 


    Steve


     


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