bugbear
Established Member
RogerS":yw03p2bq said:
Actually, it was intended as a perfectly reasonable question, to which I continue
to invite a reasoned answer.
BugBear
SWA 2 core 120 sq mm cost for 800 m ?
- Thread starter RogerS
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Actually, it was intended as a perfectly reasonable question, to which I continue
to invite a reasoned answer.
BugBear
RogerS
Established Member
bugbear":14o9j2jb said:
Well, if you really must know then the answer should be obvious. Of course I trust him otherwise I would not be using him. But he can't get round to giving me an estimate for a few days or more. I need to have a ballpark estimate sooner then that. Hence my thread. OK ?
Roger if I may ask, this is related to your thread incoming-mains-question-t101104.html.
Why are you considering a private mains cable, would you not be better in asking the DNO to extend and site the mains at the house?
Will you be the sole owner of the land in which this cable will be laid?
I ask as, if you're digging to bury your own cable wouldn't you be better off doing the "civils" for the DNO cable and subsequent works.
There's no biggie in having a private buried cable, and one of this length is of no consequence either, except for if it faults or gets damaged in any way you will need to get someone out to repair it. Then obviously pay for that repair and all this could lead to a delay in getting the power back on, and I know myself out in the sticks that ain't funny.
I've also known private cable damages to cause the relevant parties seeing the inside of courts.
Most DNOs see a no supply as urgent/semi urgent and their response times are pretty good. They also have the benefit of the fault location equipment that's almost these days nearly centimetre perfect. Without this equipment fault location is 9/10 times a "cut and test" game until the faulted section is identified, this can be many man hours = great cost.
I've personally spent days on fault location and I've had some clever tools at hand. Granted I'm up in the higher voltages and the costs just spiral, but fortunately I've never had to foot the bill.
120mm, yea that's pretty cool. Something you can get your teeth into. Professional cable wrestling, by 'eck that's fun :lol:
Why are you considering a private mains cable, would you not be better in asking the DNO to extend and site the mains at the house?
Will you be the sole owner of the land in which this cable will be laid?
I ask as, if you're digging to bury your own cable wouldn't you be better off doing the "civils" for the DNO cable and subsequent works.
There's no biggie in having a private buried cable, and one of this length is of no consequence either, except for if it faults or gets damaged in any way you will need to get someone out to repair it. Then obviously pay for that repair and all this could lead to a delay in getting the power back on, and I know myself out in the sticks that ain't funny.
I've also known private cable damages to cause the relevant parties seeing the inside of courts.
Most DNOs see a no supply as urgent/semi urgent and their response times are pretty good. They also have the benefit of the fault location equipment that's almost these days nearly centimetre perfect. Without this equipment fault location is 9/10 times a "cut and test" game until the faulted section is identified, this can be many man hours = great cost.
I've personally spent days on fault location and I've had some clever tools at hand. Granted I'm up in the higher voltages and the costs just spiral, but fortunately I've never had to foot the bill.
120mm, yea that's pretty cool. Something you can get your teeth into. Professional cable wrestling, by 'eck that's fun :lol:
RogerS
Established Member
Cheers, n0legs, for the pointers. Are you one of those super-stars who go out in all sorts of inclement weather to restore our power when the lights go out ? If so then my hat is off to you, Sir.
To answer your question..yes, it is. I have got a budgetary quote from the DNO - one is to T-off the existing 22KV line and instal a separate overhead supply to us. An eye-watering £32k. The downside is that I will require wayleaves from the landowner and he is a decent bloke and will probably say OK but that all takes time. Plus the poles will go past a house with a couple of retired old ladies in and TBH I don't really want to spoil their view if possible. Of course, it may not obscure it but just bearing it in mind.
The other quote is to underground the 22KV line following the same route as the existing supply cable and over which I have automatic rights of access etc. That comes in at a buttock-clenching £62k :shock:
Looking at rough costs from the links here an 800m run looks as if it will come in around £15k. I have to do the trenching for that but then I also have to do the trenching for the DNO so no difference there.
Or we just stick in a time-delayed RCD at the remote meter end and an earth spike at the house and hope we don't have any intermittent faults. Oh yes, might be a good idea to get the inhouse metal water pipes earthed :shock:
To answer your question..yes, it is. I have got a budgetary quote from the DNO - one is to T-off the existing 22KV line and instal a separate overhead supply to us. An eye-watering £32k. The downside is that I will require wayleaves from the landowner and he is a decent bloke and will probably say OK but that all takes time. Plus the poles will go past a house with a couple of retired old ladies in and TBH I don't really want to spoil their view if possible. Of course, it may not obscure it but just bearing it in mind.
The other quote is to underground the 22KV line following the same route as the existing supply cable and over which I have automatic rights of access etc. That comes in at a buttock-clenching £62k :shock:
Looking at rough costs from the links here an 800m run looks as if it will come in around £15k. I have to do the trenching for that but then I also have to do the trenching for the DNO so no difference there.
Or we just stick in a time-delayed RCD at the remote meter end and an earth spike at the house and hope we don't have any intermittent faults. Oh yes, might be a good idea to get the inhouse metal water pipes earthed :shock:
RogerS":1teqq3us said:
I was, I'm now sharing a seat with my a$$,.
I managed to get off the tools, progress apparently :roll: I was born to be a cable jointer, loved it to be honest. But you do a course then another and another and another, get some more qualifications and before you know it someones calling you sir and you're attending meetings :lol:
Christ I knew they weren't cheap but that's bloody outrageous for a "new" supply to an existing customer. And wayleaves, don't get me started.
Farmer---- " you see it's my best bit of land"
Wayleave Officer---- " so I'll add another zero?"
Honestly.
The 15K don't sound so bad when stacked against the DNO quotes.
Can the cable suppliers do you a 800m drum or will it be three 250s and a cut length?
What's the spark said about laying it, does he/you want it ducted?
RogerS
Established Member
n0legs":1w75w3bp said:
Haven't got that far. He's tied up with other stuff. Joining it? Do they make chocolate blocks that big ?
RogerS":fcdisi54 said:Haven't got that far. He's tied up with other stuff. Joining it? Do they make chocolate blocks that big ?
Not choc blocs but something a lot better :lol:
Roger if you need any help on the laying, jointing etc don't hesitate to ask. This sort of thing has been my life for nearly 30 years, there isn't much I don't know about sending large volumes of electricity down dirty great cables.
My employers, as they are so fond of reminding me, spent thousands on my education and training. Been to everyone and anyone who's worth listening too and I've got accreditations up the ****hole.
Raychem--- yup!
3M------- yup!
AWCO----- yup!
BICC---- yup!
Pirelli -----yup!
Henley---- yup!
etc, etc, etc.
Stop it n0legs you're just showing off now :lol:
RobinBHM
Established Member
Ive always wondered how come when running a longish cable down to a shed there is alway the concern about voltage drop and yet the domestic supply into a house isnt tree trunk sized. Surely houses arent all the same distance from a transformer.
Also is it true that domestic supplies are thress phase with single phases going alternately down the street.
£15k def sounds better thsn £62k!
I have a feeling 120 sq mm cable is not very flexible and I guess itll need more than a pair of screwfix side cutters to terminate.
Also is it true that domestic supplies are thress phase with single phases going alternately down the street.
£15k def sounds better thsn £62k!
I have a feeling 120 sq mm cable is not very flexible and I guess itll need more than a pair of screwfix side cutters to terminate.
RobinBHM":14gk7942 said:
It's to do with the shear volume we are sending out into the street.
Most low voltage mains (well in my area at least) are protected by 250-400A fuses each phase. Add that to the size of the mains, somewhere between 70mm and 300mm conductors and you've got a very capable system. Then also factor in most substations are within 500-1000 metres of each other and they're running at 11Kv obviously dropping down via the transformer to 415/240.
To be honest we have more trouble trying to get the voltage lower to the 230v spec we've agreed to adopt. I've lost count of the times I've changed the tappings on transformers.
Most new supply cable is a concentric 16-35mm single phase, and again here, we look at approx 40 metres maximum run for the service/supply to the property
I forget the rules and regs on LV these days, I concentrate on 11Kv and above, but it's still a fairly simple set up.
The mains in the street is a three phase cable and at points along it's length the service joints are done, tapping off for the supplies to the houses. At each joint we try and balance the load by connecting the houses one to red, one to yellow, one to blue. This is repeated until all the houses are serviced.
Planning engineers look at the required loading and size everything to suit. When I was still on the tools we were left to choose the phasing ourselves, as long as it would end up fairly balanced. I believe today the jointers are given instructions on the job cards.
I just realised its brown black and grey these days for the phasing. Up in the bigger voltages we use 123 or abc.
Hacksaw and an adjustable spanner :lol:
No I joke, we have big core cutters that depend on strength of the individual. We still do use hacksaws and junior hacksaws, all insulated.
There's also hydraulic cable cutters, mine would cut a 400mm three core in about 1 minute in one go. There's always the Stihl saw for some of the biggest.
It's bloody heavy stuff though, we used to have little games. Who could bend a solid core 300 around their neck etc, :lol:
A few metres of some of the cables, and I'm talking 2 or 3 metres here, will have you on your knees in about 10 yards. On days when we had a load to lay we'd all muck in with the labourers, but would be praying for the JCB to turn up and drag it in. And in the cold weather.... forget about it. Waiting for the temperature to rise so we could get it laid or warming it up with a blow lamp as it comes off the drum. God I don't miss those days.
We cable jointers develop a good grip as well, seriously. You used to get one of my old bosses who wouldn't shake hands with any of us. My old mentor Clive"Jack hammer" Lewis had had hold of him years ago, broke three fingers apparently. Well so legend had it :lol:
I'm going to memory lane it a moment.
Back in the '90s when I was still working for a living I had a servicing job to do to at factory in Newport. A new 300mm three phase service was going in. Terminated in a 400A cutout. Mains straight joint onto a previously laid main cable.
Anyway on my way down we called into our local cafe for a breakfast. My labourers would already be on site getting the hole dug and the cable laid. Just about to walk in the cafe and the phone goes, "Al' don't rush down we can't get the cable in!" Okay's my answer, going for breakfast. After a good fry up we get own there, and it's blue murder down there.
My boys are ripping into the site agent, he's firing back into them. What the F is going on. Dai tells me they've been trying to push the cable up the fitted duct line into the building, but it's blocked. The agent is saying it isn't blocked. Okay, okay just "flush it" I say.
So Malcom fires up the hydrovane and we start to drag the hoses in. So with a few plastic bags we seal the top of the duct then poke the air hose in. Sure enough the duct blows clear, no blockage. See says the agent, it's clear. Right says I, lets get this EFFing cable up this pipe.
Jesus H Christ!! About 2 hours later and we've got nowhere. We can get in about 1.5 metres and that's the lot. So I'm off on one and go for a smoke. Well I take a little walk around the site and get talking to a few of the lads. "Having trouble round there mate?" says the one guy. "Aye you could say that" I say. The other guy pipes up "I told him three weeks ago those 6" 90 degree bends ain't no good for a duct". "Eh??????" says I. " yea mate he shoved a drain bend on that black ducting of yours".
Right. Round I go. Shout at the boys, "Pack it all up lads, get out of here". Smiles all round.
The agent comes over "where you going?"
"We're off mate". "Why?" So I let rip. "mate if you can get that ****ing cable up that duct, WITH A 90 DEGREE BEND ON IT, you're a better man than I gunga din". "well it needs a bend for it to come out of the floor". "Not a ****ing 90 it don't"
I could've quoted him the minimum bending radius for a 300 cable (300 is about 80-90mm diameter and made up of 3 solid core aluminium conductors), but I decided I wouldn't.
All I say is "I'm signing my job sheet with unable to complete and the reason why. There's the cable. You get in and give the office a ring".
Fortnight later the job card comes my way again, site ready. So down we go. There's the cable, ready for jointing outside. In we go, there's the cable sticking up from the floor surrounded with a brand spanking new patch of concrete all the way around it.
Along comes this guy. "Hi boys, I'm the new site agent" :lol:
Sorry about that.
Back to the point.
The connections these days are all mechanical, basically bolt on/clip on and tighten. I was taught in the days when we used to plumb/solder the cores together. A metal pot full of solder and a pair of ladles.
The cores would be clamped up in a weakback ferrule, fluxed and soldered together, all done while the cable was live. At HV we do turn it off :lol: , but we used to solder that as well.
We weld some of the bigger voltage joints, depends on spec and type of conductor.
For LV a lot of the connectors are of a pre-insulated design these days and lots of the insulation these days is heat shrink , but a self adhesive plastic patch wrapped up with Scotch tape is quite a common method of insulating a connection. It depends on the system being bought in and the make up of the cable, aluminium or copper etc.
There you go a brief history of supply cable jointing and construction, that was fun.
RobinBHM
Established Member
Many thanks n0legs, a fascinating insight and great anecdotes.
Adjusting tappings on a transformer makes perfect sense to adjust output voltage.
Adjusting tappings on a transformer makes perfect sense to adjust output voltage.
RobinBHM":2f8ihj8p said:Many thanks n0legs, a fascinating insight and great anecdotes.
Adjusting tappings on a transformer makes perfect sense to adjust output voltage.
No worries Robin
Many people stop and watch us at play but we don't have the time, most of the time, to explain how and why we do it and you know us craftsmen we love to talk about our trades.
You should try explaining to someone at 2 in the morning why they're off supply but their next door neighbour is still on
It goes something like:-
"three what did you call it ?????????, and I'm on a different one to them. I want the same as them" :roll: :lol:
Many people see it as a "black art" but it isn't really, it's technical, sometimes a little risky and most of the time hard work.
Adjusting tappings....... Well all I can say is, You can please some of the people some of the time but you can't please all the people all of the time :lol: :lol:
I've heard:-
My lights are too dim, my lights are too bright, my washing machine goes faster, you've killed all my fish, the tellys brighter and louder, my mower won't work in the back garden.
But we try our best :lol:
skipdiver
Established Member
And here's me contemplating fitting the outside lights for my workshop because i can't get my nephew back to finish what he started and i'm worrying about a 1.5mm cable run 5mts long. Mind you, electricity is dangerous stuff, whatever size cable it runs through.
Some great stories there nolegs. I love working at home and have no desire going back out on site but i do miss the craic.
Some great stories there nolegs. I love working at home and have no desire going back out on site but i do miss the craic.
HOJ
Established Member
n0legs
That all brings back memories, never worked on HV though, I went from big armoureds for industry and then the EEB, and British Rail to working for BT on 50micron blown fibre optics.
Oops meant RogerS not RobinBHM
Will the DNO not contribute, I did a project a few years ago and had to arrange to move the 11kv overheads and transformer and reroute underground all the LV services to a cluster of rural cottages we paid £5520.00 out of the 18K quoted cost.
That all brings back memories, never worked on HV though, I went from big armoureds for industry and then the EEB, and British Rail to working for BT on 50micron blown fibre optics.
Oops meant RogerS not RobinBHM
Will the DNO not contribute, I did a project a few years ago and had to arrange to move the 11kv overheads and transformer and reroute underground all the LV services to a cluster of rural cottages we paid £5520.00 out of the 18K quoted cost.
bugbear
Established Member
n0legs":8tvs99vh said:
If you're feeling educational, you might like to explain why higher voltage (and lower current) gives less losses for the same power transmission.
it's the heart of this conversation, I think.
BugBear
RogerS
Established Member
HOJ":2miiztbg said:
I think you mean me and not RobinBHM ? A nice idea but they've not offered.
RogerS
Established Member
bugbear":3jtnsbdl said:
I'll have a go. It's called I squared R....the power dissipated in a resistance. In this case the resistance is the cable and the current is what's flowing through it. So, say I was consuming 10 Amps at 220v (rounded down for simplicity of maths), as far as the electricity company is concerned, they are only having to supply 0.2 amps (excluding any losses in the transformer),... 0.2 squared is a lot less then 10 squared.
By the by, my electrician got back to me today having had the time to sit down with the tables and work out the actual cable size needed as opposed to various people offering me fingers in the air figures of 120 or 150 sq mm.
Definitely man-sized at 240 sq mm :shock: and nearly £30k + just for the cable (inc VAT). Think that route is a non-starter.
No skills
Established Member
Wow, stone the crows.
bugbear":6bu982q3 said:
If Rogers answer will suffice, and he's pretty much nailed it, we can leave it there.
I can, if you want a more detailed answer refer to my books and write you out the full specifics. Just not now sorry, the good woman's mum died today and I'm only checking in here as a distraction.
I will add though very quickly.
By using the high voltage/low current system we achieve an efficiency in transmission up in the 90-95% range.
The other main reason is the conductor sizes. Which in turn makes a huge cost saving due to less materials. The weight saving in the overhead lines is a massive factor again affecting costs.
Just a quick one.
In the '80s we were asked to drop some EHV line and put it underground. At one of the many meetings someone pulled out an old report which had calculated the cost of removing all the overhead lines country wide.
It showed if that was carried out we would paying, back then, at least eleven times the cost per unit for our electricity.
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