this post was submitted on 11 Nov 2024
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Overhead transmission lines are so 1950s.
Invest in your country.
Japan is earthquake country so they get a pass.
India however...
Japan is slowly burying all their overhead lines into the sidewalks. A lot of urban streets look so much nicer now than they did 10 years ago.
It’s probably no worse in an earthquake than the water mains, which would inherently be a lot more rigid than cables with intentional slack built into every segment.
Afaik, the problem with buried cables is that in case of a flood or tsunami they might break, get exposed and electrocute someone.
Is that less likely to happen if the pole is knocked down instead of the line dug up?
No idea, that's what I've been told, but Japanese engineers usually know what they are doing.
I know that a downed power line is very visible, especially if it's live and touching water! I wonder if it's underground if you might miss the signs
Are they really safer in an earthquake though? Those poles could fall over and people could get caught under the cables, worst case while they're still under high voltage...
Yes im encouraged by seeing them use those machines to put things in the ground. I had not realized how effiicient it had gotten. May be cheaper than the poles hanging now.
Still about a 10x cost difference, plus (particularly on transmission lines) there's issues with extra capacitive loading.
so 10x more expensive for buried? if so I am really surprised because those machines seem like less than having the cherry picker and such. Granted though I think it only really works were you have long spans of soft soil. If its all concrete your not going to be able to do it. I would hope in the concrete thing though that tunnels would be available for this infrastructure.
Boring through rock is super slow and expensive, plus now your tunnel needs to be big enough to walk & run machines through, and needs aircon to keep it cool. It is done, but usually only in CBD areas where you need lots of cables and room for future expansion. Google 'cable tunnel' and you'll find lots of examples. Trenching machines go through very expensive consumable digging teeth whereas bucket trucks are just a fancy forklift, burning fuel and needing hydraulic & engine maintenance.
With high voltage cables, the (really thick) insulation gets really expensive, plus you need more conductor (copper/aluminium) because the insulation needs to stay cool. Aerial lines are directly air cooled (better cooling), and can run hotter, because the limit is the metal getting too hot and sagging, not the plastic degrading. Glass insulators are only needed at every tower and can be easily replaced.
Because keeping the conductor small is important, you need to use expensive copper rather than cheap aluminium for cables.
You also need regular joints which are very labour intensive, because they have to be perfect and you can't make a cable the full length because you can't ship a drum that big.
If a cable fails, fixing it is much harder than fixing an aerial issue. There was a cable fault in LA in 1989 that took 8 months of round-the-clock work to fix. When a tower falls over (usually because of slope failure or undermining), temporary structures are usually up in a couple of days.
Digging trenches under roads is much more invasive than pulling cables over roads, and rivers are even worse to deal with. It's very common for underground cables to be converted to overhead when they cross a river before heading back underground.
The Western HVDC Link between Scotland and England was built as an undersea cable because it's so hard to get planning permission and land rights to do major projects in the UK, as High Speed 2 found out.
So what I have seen is these machines that push them through earth. We do get a lot of commercials in the area telling people to call a number before they do any digging on their property. They come out and mark where the cables are. We did end up having a condo thing where power was knocked out because the guy mismarked the area. He actually came back after and tried to put correct markings in. I heard he got fired.
Yeah, directional thrusting is a thing. It was used a lot when contractors were installing NZ's new fibre network about a decade ago. I don't think it's in as widespread usage for power because power cables tend to have much wider bending radii.
This sorta surprises me as I would think the fiberoptic would be worse than copper. I guess the thing ones could roll up pretty good but we had to be much more careful with them than the copper internet at least.
Fibre needs bigger bend radii proportional to the cable size, but they're still rarely over 15mm diameter cables so you can bend them in like 150mm.
Once you start getting to 11kV MV cables, they do like 2m bend radii.
Investing on your country would be connecting more people to electricity not make the sky look better
The sky looking better is just one thing. No more blackouts when there’s winds or thunderstorms or just stray branches is the real perk.
Interestingly, underground lines aren't feasible in my hometown because of how close the water table is to the surface. Any trench deep enough to bury cables in would have to worry about flooding with groundwater or saltwater in some places.
The water table is so high that not only are there many places where basements would flood 100% of the year, but the majority of homes still have septic tanks instead of town sewage lines, and you can find houses where the lawn has been raised up with 3 or 4 feet of concrete to raise the septic tank to comply with modern regulations to avoid contaminating the groundwater supply.
I’m 4 meters below sea level. We don’t have basements because the buoyancy of the empty space would cause the houses to literally float on ground water. But we do have buried power lines.
You are being lied to.
Slab on grade crew!!
Thanks for the idea, but have you considered spending it all on bombs instead?
My house has buried lines! ...from the street to the house only... 🥺
There are benefits of overhead lines. They are cheaper to install, maintain, and repair. Diagnosing problems are much easier as well. They're certainly uglier and easier to damage but you don't have to dig up the road to fix them.
Newer cities shouldn't install overhead lines but to have old cities with overhead lines switch to underground ones is very expensive and takes a lot of time, something smaller cities likely don't have the budget for.
You don't have to dig up the roads to fix buried power lines any more than you have to tear up your walls to replace power lines in your house: you install a conduit (basically a pipe) under the road once and if the cable somehow gets damaged and needs to be replaced you can just run new cable through the existing conduit by simply pushing it in on one end and pulling from the other.
Transformers and other non-cable equipment are typically housed aboveground in little boxes or built in to the house, so they're actually easier to maintain than if they were installed aboveground on a pole since you don't need a cherrypicker to access it.
Obviously in a less wealthy small town with existing overhead infrastructure it doesn't make much sense to move it all underground "just because", but if you're already trenching under the road to install water/sewage/gas mains, it won't cost much extra to throw down an additional one or two smaller conduits for running power cables or telephone/cable/fiber lines.