efli question

Discussion in 'Electrics UK' started by andy1984, 22 Aug 2006.

  1. andy1984

    andy1984

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    in regards to the 2391 practical.....

    1, for the external earth fault loop impedance, do you disconnect the earth coming into the 3 phase db from the main earth terminal? have heard conflicting methods of this, some saying yes because of the pp's and some saying no because its a test board????

    2, similarilly, when doing the ze at the single phase cu do i disconnect the earth from the earth terminal in the single phase cu or leave it in??
     
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  3. Lectrician

    Lectrician

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    If the single phase CU is a submain (don't recall one of my AM2?) - the you do a Zs (called a Zdb).


    For the main TP board, you should disconnect the earth from earth bar - I recall being able to do this by dropping a link on the bar. (as is required by bs7671 in fact).
     
  4. andy1984

    andy1984

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    and can anyone confirm the proceedrure is

    measure L1-E,L2-E,L3-E and record the highest value as ze????

    and for fault current

    L1-E,L2-E,L3-E and then L1-N,L2,-N,L3-N . whichever reading out of the 6 gives the highest value is doubled and recorded. is this correct or have i missed something or got anything wrong???
     
  5. Spark123

    Spark123

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    You've got it.
    Btw if your tester can do 400v tests you can use it L1-L2, L2-L3, L3-L1 as well. Don't need to double these.
     
  6. andy1984

    andy1984

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    cheers spark. got a megger mft1502, believe it can do the 400v tests but ill check of course.

    does that mean i can not bother with any of the 6 tests and just do l1-l2,l1-l3,l2-l3 then because one of these will be the highest?
     
  7. Spark123

    Spark123

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    I would say you still need to complete all the tests, the phase to phase are almost definately going to be higher than phase to neutral/earth unless there are a couple of reduced phase conductors upstream (unlikely I know).
     
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