Identifying single phase overhead supply lines and looped supply

I was in discussion with an engineer from the local DNO recently and he told me that having two houses connected to a single  phase overhead line was the same as having a looped supply and would require unlooping for EV charge point installation. Makes sense, but not something I have thought about before. I wonder how many EV charge points are connected in this way, I may have done a couple.

So the question is how do you identify a single phase supply line.

I the street we were discussing at the time, 3 phase and single phase were easy to identify because for the 3 phase it was obvious that there were multiple cores twisted together on the overhead 3 phase cables, is this always the case.. When it's not obvious how many cores are in a overhead line what other clues are there. If the feed to a pole is underground and only the link from pole to house is overhead how do you know how the pole is supplied. This is the case in my village, each pole has at least 3 or 4 houses on it, I assume this is a 3 phase supply. I hope it is because i have installed 3 charge points in the village and am aware of a few more, some poles have at least 2 EV charge points connected.

I wonder why I have never seen this addressed in BS7671 or anywhere else.

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  • I was in discussion with an engineer from the local DNO recently and he told me that having two houses connected to a single  phase overhead line was the same as having a looped supply

    I'm hoping he meant as in one branch "service" span feeding two houses, rather than two (or more) houses tee'd off individually from a single phase main running along the road (as sometimes seen in hamlets or small villages with only a single phase HV supply) -  sorting the latter would be "Interesting".

      - Andy.

  • Andy, sorry I don't understand what you are describing with the two options?

  • "Main" in this context  is normally referring to the fat stuff running down the street in 100mm plus cross-section (could be 185 or even up to 300mm if the run is long), while the "service" are the branched off bits from that main that only feed one property each (well usually !) and is noticably thinnner at 35mm2 ( or maybe 50mm2 in a long span.)
    The main may be ABC or spaced singles, while the service is normally either in singles or concentric but not always.

    Mike.

  • ABC - Aerial bundled cable - looks like plaited or twisted singles. Less prone to single line breaking if a tree falls than singles, so prefferred when upgrading.

    https://en.wikipedia.org/wiki/Aerial_bundled_cable

    The photo  on that page shows the mains and service lines quite clearly,and the grey pole top fuse or link box.

    This however is LV singles (probably L L N E TNS split phase)  under 3phase 11kV from a pole-pig.


    Mike

  • Fair point - I did struggle with the words... how about a picture:

    I'm suggesting the alleged problem exists with houses 3 & 4, but not 1 or 2 - even though 1 & 2 could equally be described as "two houses connected to a single  phase overhead line".

       - Andy.

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  • Fair point - I did struggle with the words... how about a picture:

    I'm suggesting the alleged problem exists with houses 3 & 4, but not 1 or 2 - even though 1 & 2 could equally be described as "two houses connected to a single  phase overhead line".

       - Andy.

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