Joining cables - Why I'll never complain again - Page 1
Forum section: electronics / general

author: Faith
author_rank: Unknown
timestamp: October 06, 2016, 04:37:49 am
content: Wow thanks for this post. This video was really interesting!I've once witnessed a submarine cable being repaired and that too was a really lengthy process.But this really needs muscle!Just curious though, any idea what the purpose is behind the copper gauze covering the entire inner joint?Also found it cute how there's a bracket to hold up the jerry can haha.

author: Brumby
author_rank: Unknown
timestamp: October 06, 2016, 06:16:43 am
content: I'm not sure of the copper gauze - but since both cables had a copper earthing jacket, the gauze would bridge the join, maintaining this and, I suspect, offering some protection.It is certainly not a safety earth. The earthing around the original cables wasn't particularly heavy duty, so obviously the classic stake driven into the ground at the substation would be for safety.

author: H.O
author_rank: Frequent Contributor
timestamp: October 06, 2016, 08:03:23 am
content: My guess regarding the copper gauze is that it forms an all-round protection/jacket of the joint. If an excavator or whatever digs into the cable there will be a short circuit from the inner conductor, thru the shovel, to the gauze and over to the heavy gauge earthing braid which was connected to the (earthed) metal jacket(s) of the cables. The gauze may look "thin" but the total cross section is probably not that far from a single conductor.

author: jpanhalt
author_rank: Super Contributor
timestamp: October 06, 2016, 09:54:19 am
content: Gauze for EMF shielding?John

author: mzzj
author_rank: Super Contributor
timestamp: October 06, 2016, 10:40:25 am
content: Quote from: Faith on October 06, 2016, 04:37:49 amfound once even more tedious cable repair videos from youtube, AFAIK it was a japanese "project"

author: Red Squirrel
author_rank: Super Contributor
timestamp: October 06, 2016, 11:53:24 pm
content: Wow that's quite the task, is that a regular high voltage power cable for underground, or is that more specialized?Another fun one is 900+ pair telecom cables. I'm glad I'm not the one that has to splice that at -40 when a dump truck rips one out of the poles because they forgot to lower the box. (that's happened. lol)

author: edpalmer42
author_rank: Super Contributor
timestamp: October 07, 2016, 03:33:34 am
content: When I started watching the video I thought it was going to be a phone cable. But I was thinking it was rather small so, what's the big deal? Yikes!I was surprised to see that it had a lead sheath. Phone companies stopped using those many years ago.What was he measuring when he was checking the phasing? Obviously the line was dead so it wasn't voltage.Ed

author: Back2Volts
author_rank: Unknown
timestamp: October 07, 2016, 03:05:15 pm
content: Very interesting !

author: elimenohpee
author_rank: Contributor
timestamp: October 07, 2016, 06:11:39 pm
content: You don't think about the amount of design/production effort that goes into simply splicing a cable like that. Crazy.

author: jitter
author_rank: Frequent Contributor
timestamp: October 07, 2016, 06:21:53 pm
content: Quote from: Red Squirrel on October 06, 2016, 11:53:24 pmThey were speaking my language, so that video must have been made in the Netherlands.Since we're on sandy soil, putting cables in the ground is easy. Only high voltage transportation lines are overhead, all the rest is underground.In the video they were usingthiscable joint suitable forup to 12 kV. So most likely the power line is a 10 kV one likethis one. Note how they only use the earth strap and not the gauze around the inner case in those photos.

author: jitter
author_rank: Frequent Contributor
timestamp: October 07, 2016, 06:24:27 pm
content: Quote from: edpalmer42 on October 07, 2016, 03:33:34 amThe lead sheathed cable is probably an old one.This video is not about a repair, it looks more like an extension. Notice how elaborately that old cable was constructed and how relatively simple the three new cables are.

author: SeanB
author_rank: Super Contributor
timestamp: October 07, 2016, 06:29:32 pm
content: Very common, but those cables are both new, here you will not really have an issue removing the steel tapes, as they will be mostly rotted away.The copper gauze is there to equalise the voltage stress on the cable, so there is no area which has a higher or lower voltage stress on it, so there is lower risk of a corona discharge which will fail the joint rather spectacularly, I have seen where a 33kV cable joint excavated itself from under 6m of road when it detonated, leaving a 10m crater in the road. Luckily at 3AM, when there were no vehicles going along the road.Note as well there are no sharp points anywhere in the joint. The edges of the semiconductor layer, which is there to keep voltage gradients even along the cable diameter, the bevel on the inner XPLE insulator, and the breakaway bolts on the actual splices along with them having a tapered edge, are all there to keep the changes as smooth as possible. No sharp edges on the outside of the conductors and no non radiused edges on the jointing connectors either.No square cuts on the insulation of the XPLE, and the paper tapes are kept soaked in oil to keep the insulation resistance high.Filling with a silicone isolator fluid as well makes it easier to join, otherwise the common kit here has a whole load of extra tapes and heatshrink sleeves you apply over each conductor, along with filler pieces of both silicone rubber tape, amalgamating tape and 3M #33 insulation tape as a cover, for making each of the 3 cores both as smooth as possible, and so there are no air pockets inside the joint to have an arc form in them.The inner cover is there as a structural member to hold the join, and then the outer one is there for environmental protection, it actually is not a stress member, only a protection device.Spent a fun 3 hours one day watching the crew doing one joint, as I was doing a delivery to a company, and drove in just before they dug up the entrance to deliver, and had to wait 3 hours so they could do the first of 2 joints so I could drive out over the temporary duckboard they had there. The first join was right in the driveway, and I was in a line of trucks waiting for them to put the planks and boards over the trench. To add to the fun it started raining a light drizzle while they were doing this, so I held an umbrella over the worker in the trench so the cable would not get wet too much.Those kits are great though, comes with all the consumables you will need mostly precut to size, and always has an extra 2 roll springs there ( used not only for the earthing wires, but to connect the semiconductor layers to the earth sheath as well on some cables, along with the copper tapes and straps as well) for extra strength on the earth. Also has a booklet and a separate sheet of contents, so you can check all parts are there, and follow the booklet on how to assemble the kit, so you do not end up with needing to put on a final sheath with the joint already made. Resin bags are premeasured and with a separator, giving just enough resin for each pour, with only a little extra to compensate for either a minor spill or a small casing leak, but the 3M #33 tape is there in 3 rolls for this purpose. Even has the emery tape in the right grit and lengths for each stage, along with a bottle of the right cleaning solvents and wipes for the cable inners, though the outer pitch you need to supply your own paint thinners to get it off, along with the cloth.

author: SteveyG
author_rank: Unknown
timestamp: October 08, 2016, 06:09:19 pm
content: Bit naughty with the lack of PPE. The oil in the PILC is pretty nasty stuff.

author: SeanB
author_rank: Super Contributor
timestamp: October 09, 2016, 02:29:59 pm
content: Quote from: SteveyG on October 08, 2016, 06:09:19 pmDepending on when the cable was made it will either be PCB oil or a very pure transformer oil. Pre 1970 cable it will be PCB oil, and if it was made pre 1930 ( yes, plenty of those cables around and still in use) the oil will be whale oil. Post 1980 it will be mineral oil, with some being a silicone oil blend as well.So handling the new cable ( new one, it has a shrunk polyoleofin cover over the steel tapes, not a jute or hemp overwinding that is pitch covered) without PPE is not too bad, just a risk of contact dermatitis, and the cleaning using a solvent without gloves is a much higher risk for that.

author: mikeselectricstuff
author_rank: Super Contributor
timestamp: October 09, 2016, 03:13:00 pm
content: Wonder how much that cable costs per metre..

author: LabSpokane
author_rank: Super Contributor
timestamp: October 09, 2016, 04:46:15 pm
content: I must take issue with one portion of the video. What is colloquially presented as "self amalgamating tape" is technically known in the industry as "monkey shit."

author: SeanB
author_rank: Super Contributor
timestamp: October 09, 2016, 04:49:36 pm
content: Quote from: mikeselectricstuff on October 09, 2016, 03:13:00 pmSmallest quantity you can order ( without being a municipality which bought it by the kilometer) is a 100m reel, which needs a 5 ton crane to deliver, and a 5 ton rough duty forklift to move around on the 3m diameter reel. I will estimate it at around 300 pounds per meter for the PILSWA cable, depending on actual cable type and volume you order. It can come in copper cores or aluminium core, so you get what you pay for. The XLPE cable is a lot cheaper, even though you need 3 times the length, but that is only an aluminium core cable.