Paper lead (PILC) voltage drop calculations

SuffolkSparks · Sep 25, 2024

Hello everyone,

Currently on site looking at re-supplying multiple buildings that have PILC cables currently in situ, where the cables test out good, I’ve been asked to reuse these lengths and join on with XLPE SWA.

Wondering if back in the day there was any voltage drop and current carrying capacity tables as there is nowadays so I can size the new lengths of cable accordingly? As I don’t seem to able to find anything. If not I’ll have to treat the sizes the same as PVC SWA.

Many thanks

David

binky · Sep 25, 2024

If what you are talking about is what I think you are talking about, I wouldn't even contemplate trying to keep any if that cable. It's roughly 90/100 years old, certainly pre WW2.

Andy™ · Sep 25, 2024

i wouldnt be wanting to reuse it

kerching · Sep 25, 2024

Andy™ said:
i wouldnt be wanting to reuse it

I would ( stripped) it makes very good van ballast

UNG · Sep 26, 2024

The DNO's have been reusing PILC cable for many years they just use different termination methods these days

SuffolkSparks · Sep 26, 2024

binky said:
If what you are talking about is what I think you are talking about, I wouldn't even contemplate trying to keep any if that cable. It's roughly 90/100 years old, certainly pre WW2.

The buildings these cables are supplying were built after WWII, the cables are often jointed on to near the feeder pillars and where joints have failed so these cables will be used again, and also megger out perfect.
My issue is that now I have to reinstate existing lengths of the mains but I’m sure volt drop was never a thought back then unless anyone knows differently, if that’s the case I’ll have no option but treat them the same as PVC SWA

binky · Sep 26, 2024

I rewired a house rebuilt just after WW2, all the wiring being natural rubber. The main lengths of cable were still in good condition, but where they entered any accessory, the insulation fell off as soon as you removed the faceplate. So it's not so much the cable runs, but anywhere you get a little heat build up such as accessories and bends in the cable, and once you start messing with it... Anyway, it's your choice.

The only cable I would trust at that age is MICC.

SuffolkSparks · Sep 26, 2024

binky said:
I rewired a house rebuilt just after WW2, all the wiring being natural rubber. The main lengths of cable were still in good condition, but where they entered any accessory, the insulation fell off as soon as you removed the faceplate. So it's not so much the cable runs, but anywhere you get a little heat build up such as accessories and bends in the cable, and once you start messing with it... Anyway, it's your choice.

The only cable I would trust at that age is MICC.

binky said:

I rewired a house rebuilt just after WW2, all the wiring being natural rubber. The main lengths of cable were still in good condition, but where they entered any accessory, the insulation fell off as soon as you removed the faceplate. So it's not much the cable runs, but anywhere you get a little heat build up such as accessories and bends in the cable, and once you start messing with it... Anyway, it's your choice.

The only cable I would trust at that age is MICC.

Click to expand...

I’m not entirely sure you know what cable I’m dealing with, certainly sounds like you’ve not had any dealings with it yourself, this isn’t a domestic installation but heavy commercial underground mains direct from the privately owned substations. Speaking with the old electrician that installed most of these cables, voltage drop was never a factor during original installation so I shall be treating them as SWA. Thank you for your thoughts

Tim Howard · Sep 26, 2024

Even in domestic supplies the DNO boys usually tell me that the PILC supply cables are often in significantly better nick than the cheap aluminium core concentric stuff that replaced them.
What sort of CSA are the conductors?
I'm intrigued how you would joint onto it and preserve the continuity of the Lead, are you intending crimp and resin joint with constant tension springs?

SuffolkSparks · Sep 26, 2024

The cables are different sizes, some 35mm up to 120mm, the ones I’m dealing with currently are 70mm, the Birkett joints have an aluminium split ring that I size up and then clamp down onto the lead, I open out the lead with a plastic hack knife once the required lead is taken off and get glue lined heat shrink in under the lead as far in as possible to protect the cores once the clamp is tightened up, then same as SWA bonding strap between the lead and SWA use the connectors as usual and resin up, not as much of a fan of the tension spring ones. All seems to work out well, good earth readings in all the buildings and all megger out well even after years of service

binky · Sep 26, 2024

Ok so are you talking about old style mains cabling, as in the stuff that has oil in it? Most of the DNO network around where I live is still this cable, and in serviceable condition.

Quick look at wiki shows this. If it's PCB contaminated, that's nasty and carcinogenic. https://wiki.diyfaq.org.uk/index.php/Historic_Mains_Cables

UNG · Sep 26, 2024

binky said:
If what you are talking about is what I think you are talking about, I wouldn't even contemplate trying to keep any if that cable. It's roughly 90/100 years old, certainly pre WW2.

PILC was still being installed for a couple of decades or so after WW2, many of the older electricians I worked with when I started as an apprentice back in 1976 could wipe a lead joint with a wet newspaper or a moleskin with linseed oil

Paper lead (PILC) voltage drop calculations

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