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Ze readings on a TT system

Former Community Member
Former Community Member
Hi

I have a TT system on a farm where the ze readings are

L1 = >2000

L2 = 1.43

L3 = 1.41

readings took at the henley blocks directly from the meter. There's voltage on L1 and all the 3 phase equipment runs OK.

can anyone tell me why I'm getting this high reading.


Many thanks

BR
  • 0
    A bad connection when testing perhaps. A probe not making a good contact is possible. All readings should be very similar.

    I am assuming that all phases use the same earth electrode. Or has the L1 system got a different earthing electrode that has rotted away or the earthing conductor been eaten by animals or pruned through?


    Z.
  • Former Community Member
    0 Former Community Member
    Hi BR, welcome to the forum!


    1.4 (ohms?) seems a bit low for L2 and 3, could you describe the situation in more detail or if possible a few photos would really help.


    :)
  • 0
    Weirdbeard:

    Hi BR, welcome to the forum!


    1.4 (ohms?) seems a bit low for L2 and 3, could you describe the situation in more detail or if possible a few photos would really help.


    :)


    Hello Weirdbeard,


                                     I have seen steel framed farm buildings with many feet buried in the soil where the steel is used as an earth electrode. Multiple electrodes.


    Z.


  • Former Community Member
    0 Former Community Member
    Hi

    I've got 6 rods in the ground in 3 sets of 2 screwed together plus the ground is very wet at the moment. I've changed a sub board and found this problem when testing. The zs readings at the board incomer are L1 >2000

    L2 1.78, L3 1.84, simular to what's at the main.

    ​​​The final circuits are mainly 3 phase sockets with a couple of lighting circuits. The socket below the board has the same issue but all the others have balanced zs ( 2.0 ohm approx) values across all 3 phases just to confuse me even more. 

    Thanks again

    BR

  • 0
    BR:

    Hi

    I've got 6 rods in the ground in 3 sets of 2 screwed together plus the ground is very wet at the moment. I've changed a sub board and found this problem when testing. The zs readings at the board incomer are L1 >2000

    L2 1.78, L3 1.84, simular to what's at the main.

    ​​​The final circuits are mainly 3 phase sockets with a couple of lighting circuits. The socket below the board has the same issue but all the others have balanced zs ( 2.0 ohm approx) values across all 3 phases just to confuse me even more. 

    Thanks again

    BR

     


    Corrosion at a C.P.C. connection/joint then. Do any L1 cables run in steel conduit or trunking.


    Z.


  • 0
    Are you using a high current loop tester to undertake the tests? Say at 20 Amps?


    Z.
  • Former Community Member
    0 Former Community Member
    Hi Z

    Not sure on that it's  a Fluke 1651

    With just one setting for loop test as far as I know.

    BR

  • 0
    Well, unless you moved the earth electrode of your meter in mid test, it is clearly cobblers - either your meter or its cables were not connected in the same way for all 3 phases.

    As the earth is common for all phases, and you say normal loads behave on all 3, then something must be wrong.

    Did you do the noddy test of checking the phase to ground and phase  to phase voltages? Oh and check phase to neutral- you could have one grounded phase and a flying neutral.

    M.

  • 0



    There is something about zeroing the meter before carrying out a loop test in the instructions. Also the meter may not work if overheated due to being overused.


     I am currently reading through the user's manual. 

    Fluke1651_User.pdf (tlc-direct.co.uk)


    Z.
  • 0
    Here's Duncan from Fluke.....

    Why your test leads are important | Fluke Pro Tips - Bing video


    Plus a forum chat.....Fluke 1651, Ze testing... - Electrical Inspection & Testing Forum. - Talk Electrician Forum


    Z.

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