earth neutral fault

[alan holmwood]

have any of you guys have any ideas.
had an earth neutral fault on a lighting circuit.
done an insulation test between neutral and the earth bar on the cu and get a dead short.
i diss-connected all the earths so the cu is totally isolated and i still get a dead short to earth.
i take the cable right away from the cu and still no earths connected and i still get the dead short.
any ideas.

 

[Mark.W]

What were the rest of the results like ie L-E and L-N

Did you connect L-N and test to earth?

 

[Darkwood]

I hope your not chasing shadows here, are you picking up the center tap at the dno submains, in other words have your isolated the incoming neutral (switched the main sw off)
Hope im not trying to teach you to suck eggs but not knowing your experience its a common mistake for young apprentices to fall foul of.

 

[alan holmwood]

yes the main switch to cu was turned off.
and cable tested clear.

 

[Darkwood]

Is the board metalclad by any chance im assuming you mean you still got a cu E/N short with no earth connected.
Pls correct if im missing the explanation

 

[electricAl]

Any RCBO`s ?

 

[alan holmwood]

it is a metalglad board
no rcbo's
we where changing a voltage trip to a rcd and it wouldn't stay in