Water ingress in SWA.

Well,

it`s not good.

Can it be improved?

I suspect you know the answer to your question.

Unfortunately it`s not just a bit of T & E needs replacing.

So, cost of materials, cost of labour, inconvenience of power down all adds up to a pretty penny I would imagine.

Can it be chopped and tested and the bad bits replaced?

Similar answers. May or may not be prudent alternative to replacement.

Would you be happy to leave as is?

assuming you mean the loop test for something protected only  by a 160A fuse is 0.76 of an ohm, and it is not just  a case of cleaning up the glands, then it might be fun to work out how long it would take to blow the fuse if there was a solid short at that point.  The earthing was presumably once better than this and is corroding out.

The IR results indicate not just failure of the jacket and ingress to the armour, but also damp has got a path to the live cores, so presumably a joint box has failed and is sizzling like a chip shop..

There is clearly a problem, which best case is hopefully only near to  one end, but in any case something will need replacement. If you decide not to repair or replace it just yet, and to wait for it to go bang, you should certainly  start saving up to do so pretty soon.

It's not going to get better, the armour will eventually rust and the cause of the low IR will probably get worse. The questions you need to answer are do you try to find the problem and rectify it or just replace everything and when. As Ebee has said costs, budgets, inconvenience etc start to dictate your options. I would monitor the situation while making your decisions as I assume the invconvenience if the IR gets too low will be high. 

What are the odds on the cable having more than one fault?


Is it worth trying to find the location of the fault to see if it is worth saving?


Andy Betteridge

Do you know where the water is getting in? and how long it's been going on for? I might guess it's maybe more likely to be at one (or more) of the buried joints than along a cable length (although not impossible that the  cable sheath has been damaged somewhere along the line). The steel armour is galvanised so should withstand a little moisture for a while as long as the galvanising hasn't been physically damaged (like it usually is at terminations). It might be worth digging up just the joints, cutting them out and testing the individual sections of cable - it might be that just replacing the joints (perhaps with short lengths of extra cable and an extra through joint to make up the loss in the old joint) would salvage the situation without having to dig up the lot. Not an ideal solution perhaps - I believe PVC isn't good when left completely saturated in water, although XLPE is a bit better on that score - but insulation tests on the individual lengths of cable might give you an idea of the state of things.

  - Andy.

On long runs of SWA where it is selected for volt drop rather than critical current carrying capacity, I fail to see why anyone wouldn't install it in a duct as if you work out the cost of sand/stone dust there is very little difference. Plus it means that the cable is only on site as it were for a morning rather than looking attractive waiting to be buried. And, you buy the length of cable to suit the actual length rather than hope that your initial measurement doesn't incur a diversion due to finding buried obstacles...


Regards


BOD

I'm inclined to agree - on all but the shortest  run of small cross-section (so cheap to replace) cable, the saving from direct burial is probably a false economy - and can greatly increase the risk of damage to the outer sheath from day one, unless the backfilling is very conscientiously done (whereupon cost is similar). I know the instructions always say backfill material free of flints and so forth but as soon as no one is looking, almost anything might get mashed in. However, here I think  it is too late for such advise.


Even if it is ingress at a joint, it sounds like a length from the joint to the wet end will need to be dug up.

I have seen schemes for blowing gas between the cores of the loose filled network cables, but SWA has no such void.

Thanks for the reply`s.

The cable runs up hill to the first joint which will be a least 500Mtrs.

The cable is buried in the ground over a metre down with no duct. there is no plan of the run of the cable so cat and gennie would be a start.

Then maybe a ground penetrating radar to find the joints.