I would recommend replacing the entire cable, if one part has been damaged by rodents then it seems probable that other areas of damage exist and are likely to cause future problems.

Hi, I use a Fluke 2042R cable locator and receiver, which I utilise for identifying short circuits.

Andrew

This isn't as straightforward as the cable is buried in walls/ceiling. It's only one section as the ring has been broken and it's functioning as a radial on one leg of the ring. The damaged section is difficult to trace even using the standard approach of splitting the ring taking each socket off and testing.

This looks interesting, the current 2052/2062 models are very expensive. I will look into whether they can be hired.

Yes before I bought one I did hire for a week. Wasn’t expensive.

That must mean that you have identified which section of the ring is damaged.

I agree with Broadgage that it would best to replace the whole section. If you are going to have to dig out at least a couple of feet, making it six feet won't look much worse, and the decoration will still have to be made good.

There is also the question of joining the cable, which is avoided if the whole section is replaced.

You may be able to get an idea where the short is by measuring the resistance of the two portions of the damaged section - its distance along the section will be proportional to the resistance. Granted your low resistance ohmmeter may not make much of a distinction, but it should give an idea.

Find and repair with Maintenance free joint box, meets regs and keeps the cost down.

Before getting overly technical , is it possible not to bother to locate the fault at all, but instead to isolate the dead section at two convenient points known to be good, abandon it, and then run a new cable between the known good points via another route, perhaps in rat proof containment? you will never be sure otherwise how close it is to failing again,

Mike

What is the easiest way to pinpoint where a T&E cable has been damaged

It depends on the nature of the damage. If it really is a dead short, then a decent Ohm meter should give you a rough idea of the distance along the cable to the fault (knowing the resistance/m of the conductors you're testing between) - I did that sort of thing successfully once to find a JB where someone had tried to extend a ring using a single joint box - connected L & N correctly but connected the two original ring c.p.c.s together on one side and the two extensions together on the other.

If it's less of a dead short and more the usual bridge of charred remains of insulation that mucks up an insulation test, then that method won't work.

If a conductor is broken, then (with extreme care!) energising the faulty conductor from one end and tracing using a volt-stick can work (but might come under the "don't try this at home" category).

I've seen some impressive results in the past from a TDR (time domain reflectometer?) - which is like radar but inside a cable and gives a length of cable to the fault - but probably isn't cheap to buy or even hire.

   - Andy.

AJJewsbury said:

I've seen some impressive results in the past from a TDR (time domain reflectometer?) - which is like radar but inside a cable and gives a length of cable to the fault - but probably isn't cheap to buy or even hire.

Invaluable for copper comms cable testing.

They are nowhere near as expensive as they used to be. Whilst a lot of the very cheap ones are aimed at data/comms (twisted pair/coax), I think you can pick up a Megger TDR cable fault locator for not much over £1K.