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

  • Replies 6 replies
  • Subscribers 34 subscribers
  • Views 772 views
  • Users 0 members are here
Options
You may also be interested in

AMD 4 DPC - new section 545 - functional earthing

AJJewsbury

Has anyone had a look at the proposed new section 545 (functional earthing) in AMD 4 DPC?

At first glance, it seems rather confusing (to little heads like mine at least). I can see the general point of trying to keep protective conductor currents (whether due to normal conditions or faults) from flowing along functional earthing conductors - so AFARP connect to the protective earthing system at one point only - at least for each "cluster" of interconnected equipment.  It seems to be rather prescriptive though - e.g. "If there are multiple functional bonding conductors present in the electrical installation, a separate main functional earthing terminal (MFET) shall be installed for ease of connection for these conductors. The main functional earthing terminal shall be connected to the main earthing terminal only once." - so if I had two clusters of equipment at opposite ends of a large installation, would this prevent me connecting each cluster independently to a local PE (say a nearby DB) but rather have to run all the functional earthing/bonding conductors back to one central MFET? It doesn't seem to be a good fit with the proposed 545.2 "The main functional earthing terminal MFET and the MET may be combined" nor the methods described in 444 (e.g. Fig A444.2).

Or have I missed something obvious? (again)....

   - Andy.

Parents
  • AJJewsbury said:
    Or have I missed something obvious? (again)....

    The earthing topologies, star point vs mesh (multiple-bonding) are discussed in BS IEC 61000-5-2, and are well understood.

    AMK said:
    Hi Andy. In my view, running all functional earthing conductors back to a central MFET could be more cumbersome and costly in most instances. The existing method in Figure A444.2, seems much easier to apply and clearer than the proposed methods in section 545.

    Agreed ... in most cases. There are some cases, however, where it may be relevant to control voltages (and currents) in the FE system.

    The general considerations in selecting approaches are:

    • Common-mode vs differential-mode interference or "noise".
    • Bandwidth and cutoff frequencies (of EMI or the victim system).
Reply
  • AJJewsbury said:
    Or have I missed something obvious? (again)....

    The earthing topologies, star point vs mesh (multiple-bonding) are discussed in BS IEC 61000-5-2, and are well understood.

    AMK said:
    Hi Andy. In my view, running all functional earthing conductors back to a central MFET could be more cumbersome and costly in most instances. The existing method in Figure A444.2, seems much easier to apply and clearer than the proposed methods in section 545.

    Agreed ... in most cases. There are some cases, however, where it may be relevant to control voltages (and currents) in the FE system.

    The general considerations in selecting approaches are:

    • Common-mode vs differential-mode interference or "noise".
    • Bandwidth and cutoff frequencies (of EMI or the victim system).
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