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Overhead lines, which is neutral?

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  • 21-12-2020 4:30pm
    #1
    alan4cult
    Registered Users Posts: 1,583 ✭✭✭


    When you see 4 overhead lines running pole to pole, which wire is the neutral and which are the 3 phases? I'm guessing the neutral is either the top or the bottom wire.

    Also then how do they decide which phase to which house? Is it every third house 1,2,3 and then repeat?


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    #2
    sparcocars
    Registered Users Posts: 148 ✭✭sparcocars


    alan4cult wrote: »
    When you see 4 overhead lines running pole to pole, which wire is the neutral and which are the 3 phases? I'm guessing the neutral is either the top or the bottom wire.

    Also then how do they decide which phase to which house? Is it every third house 1,2,3 and then repeat?

    Goes Neutral
    R-phase
    S-phase
    T-phase

    Top to bottom. Of theres a fifth wire on the bottom then thats a switch wire for public lighting. The switch wire is mainly redundant these days due to photocells on each light.


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    #3
    Yuser.
    Closed Accounts Posts: 91 ✭✭Yuser.


    sparcocars wrote: »
    Goes Neutral
    R-phase
    S-phase
    T-phase

    Top to bottom. Of theres a fifth wire on the bottom then thats a switch wire for public lighting. The switch wire is mainly redundant these days due to photocells on each light.

    Always wondered about the public lighting , how those lights all came on at the same time

    The switch wire wouldn't be that common or I would have noticed?


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    #4
    Lenar3556
    Registered Users Posts: 1,359 ✭✭✭Lenar3556


    Yuser. wrote: »
    Always wondered about the public lighting , how those lights all came on at the same time

    The switch wire wouldn't be that common or I would have noticed?

    Used to be, but not really any more.
    Photocells are very accurate!


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    #5
    Victor
    Registered Users Posts: 78,303 ✭✭✭✭Victor


    Yuser. wrote: »
    Always wondered about the public lighting , how those lights all came on at the same time

    The switch wire wouldn't be that common or I would have noticed?
    There tends to be a sensor every 10 lights or so, certainly on older ones. It's on top of the fitting, so it isn't necessarily very visible.

    Some look a bit like this: https://www.screwfix.ie/p/ced-black-body-opal-head-photocell-standalone-sensor/980CG?gclid=EAIaIQobChMItcim8JLg7QIVz-3tCh01dw4cEAQYASABEgJmDPD_BwE&gclsrc=aw.ds#product_additional_details_container with a bottom bracket and are about the size of you fist.


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    #6
    Sparky84
    Registered Users Posts: 173 ✭✭Sparky84


    The reason for Neutral being on top is if it breaks will cause a short across the phases and not leave a house with a broken neutral.


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    #7
    AutoTuning
    Closed Accounts Posts: 423 ✭✭AutoTuning


    Also as the neutral is earthed it would provide a degree of lightening protection, relative to a strike on one of the phases.


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    #8
    Dunfyy
    Site Banned Posts: 113 ✭✭Dunfyy


    My pole only has 2 high voltage wires


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    #9
    Lenar3556
    Registered Users Posts: 1,359 ✭✭✭Lenar3556


    Dunfyy wrote: »
    My pole only has 2 high voltage wires

    Most likely a single phase and neutral - low voltage.


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