efli question

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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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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).
 
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???
 
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.
 
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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?
 
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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