N-E fault bank holiday ruined

[MWD149]

Hi all , after some opinions on N-E fault or ring main.

After chasing this fault and ruining my bank holiday weekend , ring main IR readings as follows

L-E >999
L-N>999
N-E>0.98Mohm

I have narrowed it down to a cable spurred from ring main , astonishingly the 3no. Cables in the twin switched socket all individually test out at >999 across all conductors. It’s only when connected together that it causes the low reading , like there is a low resistance between 2 different cables ,any ideas?

TNCS supply , split load consumer unit

 

[timhoward]

Try a wander lead from the MET to each of the 3 conductors at end of the spur, with the spur disconnected at the branch point.
It could be a damaged cable touching a pipe that is bonded.

Also check end-to-end ring integrity as a broken ring can upset otherwise sound logic!
Finally double check that when the spur is disconnected at the branch point and the other two cables wago'd together, there is no fault showing up back at the board.

 

[timhoward]

When you say "connected together" is that using the original socket or a temp solution e.g. Wago's?
In other words, could it be the socket itself?

 

[westward10]

When test these disconnected cables are you also disconnecting the cpcs and only testing to them or are they still connected to the installation earth.