A train-sized tunnel is now carrying electricity under South London
ianvisits.co.uk
ianvisits.co.uk
Great job whoever was in charge.
What's the zig-zag pattern for, seems like a fair bit of extra conductor.
https://cdn.ca.emap.com/wp-content/uploads/sites/9/2018/04/l...
* Cable thermal expansion under current load: https://www.ahelek.com/news/cable-thermal-expansion-and-its-...
* The amount pictured is in excess of that required for thermal expansion. The excess is to have some spare length in case of modifications. For example if you have to replace the transformer and the terminals are not in the same location. You cannot extend a massive cable like that easily or without degrading its specs.
* The sine wave pattern makes it into AC of course (/s)
I think that's just cables sagging, which is a requirement to accommodate thermal and seismic displacements.
I don't think a utility company in their right mind would allow workers to bicycle inside a tunnel powering the grid.
I had heard that tunnels were a good first step for rolling out super conducting cables, but that doesn’t seem to be a thing.
Superconducting cables have progressed a lot. I’m assuming that setting up a cryogenic system to keep cables cool enough, in a confined space wasn’t thought to be worth it.
The tunnels look tight enough, and boiling liquid nitrogen from a leak could cause asphyxiation I imagine.
Yeah tunnels underground would be better for superconducting cables, but it is indeed not really a thing as the cooling and installing and maintainance would be waaaay more expensive, than just using higher voltage. Or if one really cares about the loss, use direct current - but we are talking aber very small distances here.
If superconducting would be easy, we likely just would have fusion plants everywhere with no need for transporting electricity long distances.
I thought direct current had higher transmission losses vs AC
Problem is they need these https://en.wikipedia.org/wiki/HVDC_converter , for these https://en.wikipedia.org/wiki/HVDC_converter_station which are expensive. So it depends on circumstances, how and when its economically feasible to use HVDC, or not.
The fact that the tunnels are 50 meter underground leads me to wonder if their main requirement comes from national security needs.
* the recent new massive and extensive sewer tunnels,
* the secret basement extensions of the ultra rich, multi story archival storage, vaults, etc,
* the new underground tunnels (rail / subway for US readers),
* old roman and other buried but still 'conserved' architecture,
* crypts, graves, plague pits,
* WWII UXB's etc. etc
is a hell of a 3D needle to thread - there's > 2,000 years of urban layering in that small area.
If you wanna knock out the grid, hit the substations and power plants.
It's a common claim on HN that when a regulator caps profit margins, that incentivizes the entity to make-work to increase absolute revenue and thus profits. But capital markets, i.e. investors, only care about marginal returns. Unless your profit margin cap is really high relative to average returns in the global market, there's no market pressure to do this, AFAICT. Capital projects require investment, but what investors have so much money burning holes in their pockets that they're eager to invest at marginal rates lower than what they could invest elsewhere?
The only financial incentive for this would have to come internally from the company, say from executives whose compensation would increase merely by dint of larger absolute revenues. For regulated entities maybe that's plausible? But typically executive compensation is usually tied to margins and given in stock.
I only just came to this realization when reading about the effect of tariffs and a description of why they drive up prices much more than you think. If the import price on a widget is $100, a 10% tariff drives it up to $110. If the next purchaser in the supply chain was originally paying $X, you might think they would just pay $X + $10, and on down the chain, so that retail prices only rise by $10. But that's not how it works. If the importer was adding 20% (not atypical), they're going to need to sell the widget at $120 + $10 + ($10 * 20%), so $132.00. The next purchaser will need to do the same, but on their purchase price. Whereas before they were selling at $120 + ($120 * 0.20) = 144.00, now they need to sell at $132 + ($132 * 0.20) = $158.40, an $18 jump, not $10. It compounds on down the chain. Why? Your investors are expecting you to add a Y% margin. The reality is a little more complex, of course. Maybe a supplier can get by with a smaller profit margin, but the floor is going to be their cost of capital for buying supply, which may be least 5-10%.
https://ee.eng.cam.ac.uk/index.php/2025/09/22/from-gridlock-...
An interesting article, I’ll download the IoP report and maybe read it.
But it talks about doing the hard work to improve the Technological Readiness Level from 7 to 9. Although these cables need rare earths so might be problematic.
Yeah, the cost isn’t worth it.
Buying two transformers to step up the voltage on one end and step down the voltage at the other end is going to be several orders of magnitude cheaper than actively cooling cables to 20K for their entire length.
Also your cryo liquid should ideally be something that doesn't do the following things:
1. Leaks — shouldn't cause asphyxiation risk to humans who need to fix the leak. 2. Broken cable due to disaster – coolant doesn't turn into explosives when in contact with high voltage high current electricity.
However, UHV DC electricity in tunnels could be financially attractive and safe if you can cool the tunnels properly (no superconducting cryo)
AC transformers are so much cheaper than DC converter stations that I don’t think this will ever be true. At the distances HVDC has a distinct advantage at, you wouldn’t be building tunnels. HVDC is mostly useful for grid ties between unsynchronized grids.
Best I found was a page talking about vertical boreholes on Old Kent Road (opposite Commercial Way which is just inside Southwark) but nothing about a substation there on any page.
[0] Estimating off the National Grid map, it's roughly vertically centred between Lewisham and Greenwich DLR stations - absolutely not in Southwark!
[1] I feel like I'm going mad - the number of pages I found whilst trying to find the exact location that said the same thing under the same map is honestly discombobulating.
But yeah, that's the place on OKR I mentioned - just inside the Southwark boundary, not really New Cross. Nowhere near the dot that nationalgrid have on their map either.
That means the path through the air to some conducting materials needs a certain distance, and that even when wet or iced over or whatever can happen up there.
The cost of oil insulated cables that can do 132kv is about £900 a meter. Whilst there are HV cables that exist on the outskirts of london, they are much rarer in zones 1-3.
I assume that the cost of pylons with raw cables is much much cheaper. The problem is planning permissions, physical clearance. planning permission and now one wants to live near HV cables (that they know of. There are a bunch of 33kv cables buried outside posh people's houses in zone 5, and a bunch in canals.)
Here’s some high-voltage cable spec sheets that show a cross-section of the assembly for voltages above 69kV: https://www.southwire.com/wire-cable/high-voltage-undergroun...
The conveyor belt to remove the debris, the machinery to place the concrete segments to form the wall.
I guess it could be shrunk, but there wouldn’t be space for people to get through
Mention is made of the North London tunnel, but in preparing for the 2012 Stratford Olympics pylons there were replaced by an Underground tunnel too, and there was a lead time of 7 years from the Stratford winning.
I would imagine trench and bury or mole-digging to be a much cheaper way to install it?
Not having an accessible way to the cable is somethibg you don't want if you don't know exaclty where and what is broken (because you can't see it).
Generally you do know where things are broken - there are tools to identify the exact location of both broken conductors and broken insulation by reflecting high frequency signals down the cable.
Seems like it would require more cable than a straight line so I am guessing there is a reason for it
TL;DR
Camera makes it look more than it is, it's mostly just sag
If you want to see electrical with significant zig zag, open up the wall of a house that was built without very detailed plans, but still hired an electrician with a lot of prior experience being told to move stuff after the fact. They just zig zag it like crazy under the drywall, so there's an incredible amount of slack to pull wire to new and exciting unplanned locations.
-gotta hang them somehow, and in a very controlled way.
-thermal expansion, very important not to cause axial strain on a cable, which happens on tight bends.
You might think it would be enough to just have slack "somewhere" but I think you get to have many many micro adjustments when you have it across the entire length.
Why don't HV telephone lines do this?
I have no idea. Maybe because they can hang and droop more easily. I hope someone more knowledgeable gives a real answer.
There are many examples of how the UK is London-centric. This isn't one of them.
Not to mention that over ground wires are manifestly better in every dimension except for aesthetics.
This is a great example:
Because it contains all of the financial services business that screw money out of all of the real businesses in the rest of the UK.
Cool to see cycling down there - much safer than on the roads above.
1. Cost per kWh transmitted?
2. Cost per person served?
3. Cost per pound of GDP generated?
Please provide this for London and the other locations you have in mind.
https://www.ons.gov.uk/economy/governmentpublicsectorandtaxe...
London is effectively kept going by these infrastructure projects and so many UK government agencies and businesses being headquartered there. Even the monarchy plays a role, as a massive gravy train mostly based there. All that money keeps other businesses in London going. Every time someone pays UK taxes in any form they are supporting jobs and physical facilities based there. The BBC is another one. People throughout the UK are forced to pay a licence fee that is mostly used to produce content in and about London.
This is part of a repeating pattern. London took massive amounts of resources such as coal, metals and manufactured goods from other parts of the UK which are now in poverty. The North Sea Oil boom of the 1980s, was used to prop up the London stock market, and only a fraction of that money stayed within Scotland which was suffering industrial decline at the time. (Aberdeen has surprisingly little to show for the oil boom and is now a city in heavy decline.)
BBC similarly, spends the vast majority of it's money outside London. If you were from anywhere near Manchester, Glasgow or Liverpool you'd know that perfectly well.
I'm afraid governments have actually done genuine work to try and reduce dependence on London to not very much avail. Network effects rule again, why is twitter (X) bigger and more popular than blusky or whatever?
1) the amount of wealth claimed to be generated in London, that was actually just financial services sucking in money from the rest of the UK
2) The cost of all the pensioners that left London when they retired, claiming their pension and health care in a different part of the country
Then a small bit of what is leached is paid back in taxes and you pretend that means the leeches are subsidising the actual workers.
It’d be super, smashing, great! for the cities to be far better connected together across the Pennines.
We're ~30 years into a new information/digital revolution and London is a world centre of it. There's plenty of wealth generation happening. People are welcome to sit and wait for it to come to them if they want.
The odd thing is that it makes fun of all those coal mining and oil producing areas whose wealth it has been only too happy to steal. A sort of internal colonialism.
And I wish people would understand how costs work.
Pylons need space right, they also need maintenance corridors and access. Every ~360m you need a space to put a pylon[1]. Can you imagine the cost of buying 400m2 every 360 in zone 1?
what about the scaffolding when you need to re-string the cables? can you imagine how expensive that would be? what about if a lorry smacks into it? Its just not practical.
I grew up in norfolk, next to a bunch of HV pylons. No-one commented on them, because they were always there. THey are going to put some more in, and suddenly "its a blot on the land scape" and its "ecological damaging" Then its proposed that the cables are buried. apparently a 200 meter clearing 30km long is more ecologically friendly than pylons ever n hundred meters.
but thats an aside.
[1]https://www.quora.com/What-is-the-distance-between-electrici...
London is the place that costs don't work. It is full of things that don't need to be there, driving up the real estate prices. The port closed decades ago, so let's move the insurance and FX markets somewhere cheaper? Let's move out the government departments too.
Modern London is all about MPs who are physically tethered to Westminster by in person voting, being surrounded by the kind of people who want direct access to MPs...
All of the companies who specialise in creaming money off real companies gravitate towards that pig trough. Today they need data centres as close as possible, so they can cream money off faster. And we now have to feed those parasites with extra power lines.
Don't lecture me on costs, while London continues to try so hard to inflate the price of the tidal mud it resides on, by sucking in the rest of the UKs wealth.
no, because this is mostly a logical fallacy.
> It is full of things that don't need to be there
Like what specifically? Most heavy industry moved out in the 70/80s, the port moved to essex in the 80s. The fish and meat veg moved out to canary wharf, and are going to move further out soon. what else should be taken away?
> Today they need data centres as close as possible,
This is a cable replacement, but yeah, lets go with new datacentres in london (as we know planning is quick and simple, so they are popping up weekly....) However the key issue is that population density is now back to somewhere like it was in the 40s (https://trustforlondon.org.uk/data/population-over-time/)
So whilst power demand is largely flat, infra doesn't last for ever, so even power cables need to be replaced.
> Modern London is all about MPs who are physically tethered to Westminster by in person voting, being surrounded by the kind of people who want direct access to MPs...
Yup, all 8.9 million people that live there are entirely there to do lobbying. I to am a lobbyist.
> Don't lecture me on costs, while London continues to try so hard to inflate the price of the tidal mud it resides on, by sucking in the rest of the UKs wealth.
Well, as you've neatly avoided any mention of costs of tunnel vs pylons, its not really a lecture is it. I hope you come to peace with the general concept of london.
In spite of devolution and the so called "levelling up" programme for other parts of the UK, London obviously continues to be heavily subsidised by the rest of the UK.
This is a farcical comment. Were you being sarcastic? The tax revenue from London massively subsidises the rest of the UK. The investment happens in London because you can guarantee it will make a return, and quickly.
London has centuries worth of investment from everywhere else based on that. That money has stayed there, and money is spent constantly on infrastructure which helps it make more money. Contrast this with Liverpool, Cardiff or Belfast which suffered decades of decline for various reasons and a fraction of the investment.
If the capital had been moved to Liverpool back at some point in the Middle Ages, then that would have remained a wealthy city instead of becoming a basket case in the eighties. The presence of the civil service and government alone would have kept Merseyside wealthy, and would have made it a huge tourist centre. Bigger than now, and even that was mostly to do with the Beatles.
By the way, the state funded Wembley refit cost more than the construction of the Scottish Parliament. Guess which one got all the negative press?
And if mass media continued to promote my area continually then the value of my home would also go up. I would get given higher wages to cope with the increased cost of living there. We would get more tourists visiting my area, and firms and non-doms would set up there because of the positive image.
Much like London.
Which is still implicitly accepting the fact that London does create more value that then goes to the rest of the UK rather than the reverse.
London is a net contributor of tax revenue to the rest of the UK, which presumably goes towards, for example, the 17 (non-London) power grid improvement projects listed at https://www.nationalgrid.com/the-great-grid-upgrade/where-it..., among other things.
The UK is often too London centric, but this project doesn't seem like evidence of it.