RCD keeps tripping on Ring main

[asthpsw]

When I turn on my ring main Circuit Breaker the RCCB for the whole board trips detecting in what I thought a leakage to Earth.
I've either disconnected every appliance from the main, turned off every socket & where there is both a fuse & a swith taken out the fuse....so basically its just the ring main but it still trips.

Using a multimeter at the sockets (I've tried a few) there is a resistance reading from either the Live or the neutral to the eath pin. Also at the cable ends at the distribution/CB box there is a resistance between the Live & the Earth also the Netral & the earth............indicating to me that somewhere in the circuit there is a leakage to earth ?...am I correct in my assumption ?

If I'm correct how do I locate the "leakage", it has been suggested to me that I could use one of these "testers" from a DIY shop that has LED's on but what does this tell me ? other than the socket is wired up wrong ?.............no changes have been done to the Ring main, no new appliances, no carpets laid etc etc.............the only thing I did was turn off the CB for the ring main to unplug the Fridge/ freezer.....& from then on its alwatys triggered the RCD.

On the DIY "tester"...does this not need current to the sockets to work ?.....which of course my RCCB will not allow !

Paul

 

[BS3036]

The current flow is either in the cable or in a load which you haven't thought of. Shaver socket, door bell transformers, wired in time-switches come to mind.

To locate the load or other fault, you could disconnect the ring from the MCB, and separate the ends. Then locate a socket at the furthest extremity of the ring and take the wires out. You can now do your resistance measurement on each half of the ring and narrow the fault position down to that half.

And so on...

What sort of resistances are you seeing?