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Why Aren't Powergrids Underground?
jonging asks: "It is common knowledge that an underground power grid is less susceptible to the effect of a large thunderstorm. The American Transmission Company cites numerous reasons why it (and other power companies I assume) do not bury their transmission lines underground (e.g. environmental concerns, cost of installation and repair, etc.). Exactly how detrimental are underground transmission lines to the environment? Wouldn't the time spent without a power outage generate more than enough revenue to offset initial costs? Aren't the need for repairs in cities with successful underground power grids rare?" The linked article goes into extensive detail about the disadvantages in initial costs of putting in underground lines, but doesn't go into any detail about the maintenance costs of either option. With storms getting worse and worse (Maryland, DC and Northern Virginia have weathered torrential downfalls this week), might underground lines prove more resistant to storm-related power outages?
Though I'm not addressing TFA directly, let me comment on the DC thing. Yes. We have been utterly hammerered unto oblivion with rain in the last 5 days. But even at that, the power grid in DC is remarkably stable.
My office, which is about 3 blocks from the White House, has never had a major event that would have an effect on our network. In about 10 months of running monitoring 24/7 on our UPS, I've never seen a major "power event" (outage, surge, something else big). I've never seen a big spike or dip. Hell, I've barely seen any variation at all in the signal.
Perhaps it's a function of living in the big city. Perhaps it really is the fact that I'm on the same power grid as the White House. Perhaps it's just a coincidence and some really nice wiring, and me with a little too much tinfoil in my hat. Regardless, I think something is special about the power grids in the DC area.
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More expensive to dig, harder to cross roads/othershit when digging, MUCH easier to repair above-ground lines than below-ground lines (all you need is a cherry-picker truck), and what would squirrels walk on if there weren't above-ground power lines?
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It's true that underground lines require less maintenance. A lot less maintenance. If we changed all our lines from overhead to underground, NES would have to layoff 4/5 of their maintenance team. Rather than realizing that it would take years to convert every powerline in Nashville from overhead to underground so they'd have excellent job security until they retired, they have decided not to convert to underground lines. I wouldn't be surprised if this is true in other areas, but I know that's the deal here. So everytime there's a thunderstorm the power goes out, and the cable goes out with it, cause the cable lines follow the powerlines.
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And you know what? I'd say it looked pretty damned nice.
You know what else? I sound like a old rambling grandpa. I remember in my day to get to Taliesin we had to walk 5 miles uphill both ways in the snow...
A guy walks into a bar... well, I forgot the joke, but the punchline is that he's an alcoholic.
Cost is about TCO, not just initial. It depends on how far out you extend your costs whether it would be worthwhile to the power companies or not. This, I have no idea.
example: We get damage in large item truck shipments. Averaged over ALL our shipments, it costs about $20 per shipment. We spent $5 per shipment to reduce it to an average of $10 per shipment (half the damage). Our net gain is $5 per shipment, plus less hassles with damage.
For about $40 per shipment, we could get almost NO damage, but it would not meet the TCO compared to just spending the extra $5. The goal isn't to stop ALL damage, it is the lowest average cost for all shipments. They are no different.
So there will be SOME areas where underground meets the TCO spread over, say, 10 years. Some won't. They key is having the guts to sacrifice short term profits for long term gains, which is tough if the CEO has stock options that expire in 3 years.
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My apartment complex has its power fed in through a buried line, and I can attest to one good reason why power companies may not want to bury all (or even most) of their power lines: water.
My power has gone out three times already, this year, due to water seeping in where it shouldn't and causing a major short. Aside from the obvious risk of losing power, there's also the possibility of pedestrians and pets being electrocuted.
~UP
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Underground powerlines would suffer higher capacitive losses than overhead lines, and losses between the generating plant and the user would be power that the utility company can't (directly) bill for.
With all the public concern about EMF exposure, the situation would be made much worse when all those distribution transformers move from 40' up a pole to concrete pads at ground level. And then there is the everpresent problem of "backhoe fade"...
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Downtown Washington rarely has power outages because the power lines are underground.
Long term it still costs more.
Its a lot harder to maintain buried conduit. Plus, there's the problems of accumulated gases in any piping you lay down, plus drainage, plus trash/dirt/crap accumulation at the manholes.
Look what happens when buried conduit deteriorates - the resulting fire is nasty because its more concentrated than in the open air.
We could continue to debate this endlessly, but maybe you could save time and just read the official report?
I'll also mention that 4 of the 5 NYC boroughs (Manhattan, Brooklyn, Queens, and the Bronx) have their electricity distribution almost entirely below ground. It was a massive investment, but it was long ago.
The answer to this is simple. Instead of running both wires from the power station to the customer, run one each way. As one cable is now reversed, the current will now not be in opposition. As you know, the opposite of destructive interference is constructive interference. You could get twice as much power out of that line as you put in!
Another answer is to move the users closer to the power stations! We should make the stations smaller and have more of them. What if every transmission pole was a power station? We should put a solar panel on top of every pole, and if we spin it around at 60 RPMs, voila! A/C!
Well, I can dream.
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Cost is about TCO, not just initial.
The above statement is true. However, the decision to spend less money on the front end and more on the back end has nothing to do with the aforementioned truth.
What matters is profit today. Spend as little money as possible today while taking in as much revenue as possible today. This makes the stock price go up today, which makes your options (someone else mentioned these) go up today, and the Board of Directors happy today.
Do not concern yourself with trivialities like "tomorrow" or "TCO" or "long-term survivability." By the time any of that comes around, you'll have jumped (or been pushed) to another company that you can squeeze the same way. If you just so happen to still be around tomorrow, blame it on the office staff for using too many paperclips, and stop subsudizing employees' soft drinks.
Once you understand that business leaders are not running businesses for the long term, or even the medium term, it's very easy to understand the (il)logic of their actions. The company exists to be soaked by execs until it dies.
(Here, let me post my own reply: "Bitter much?")
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I've been building power plants and other industrial projects for 15 years now. We encase all cabling in ductbanks (conduit & rebar in concrete, usually dyed red) and only a determined idiot will knock these lines out of service.
To address the issue with power loss through induction, yet it happens and it's dangerous. We had a run of pipe being welded up directly under a 100+ kV line leaving a substation. After getting several hundred feet welded up, they started having spot fires in the area. After several calls to the local FD, the FD Chief was getting pissed so they were walking the area down, heard a zzzzzssshhhtt (best I can describe) and sure enough the lines were inducing a current into the pipe (creating a large cap) and once the charge was large enough it arced to the ground, sometimes in a area with dry leaves & pine needles.
Also on another project we had a 12kV line in a ductbank piggybacking a 100pr data cable which fed our T1/T3 lines and we kept blowing the phone companies coils on their end and causing havoc with our digital phone system. Finally one day I was re-wiring the phone system and got zapped. Voltmeter showed 60V, not sure of amerage but it smarted. Idiots who installed the 12kV line didn't bond the shield so we had a current inducted into the 100pr.
So, yes power can be run underground but you better encase it and know what you're doing or hire someone who does.
Reminds me of this thread
The Backhoe, The Internet's Natural Enemy
Always carry a length of fiber-optic cable in your pocket. Should you be shipwrecked and find yourself stranded on a desert island, bury the cable in the sand. A few hours later, a guy driving a backhoe will be along to dig it up. Ask him to rescue you.
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There is a big cost diffrence if putting in a subdivision and burying the 7200 volt line into the subdivision transformers and burying a 500,000 transmission line. Safety is also a concern. Which line would you rather hit with a backhoe?
On a high tension line, the capacitance per foot is much higher for a buried line than for an overhead line. For long distance feeding this capacitive load adds greatly to the power loss in the line. Burried is OK in New York City, but forget it for the grid. There are too many losses. Putting the 2 top grounded lines above the high tension lines have greatly reduced lightning strikes to the power conductors and their resulting outages from damaged insulators and substation equipment.
Disclaimer.. My father was a substation operator for Bonniville Power Administration. I've seen the MegaVar meters on some long lines.
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Part of the thing *not* discussed here is that there are huge amounts of the power distro system in DC which *is* underground. The problem that they've run into - and I've had conversations with the people maintaining them - is that maintenance is a nightmare.
Getting to the underground lines is a bear and then making any changes is even worse. In most scenarios, they actually wait for the equipment to fail (eg. ignite and/or blow up) before they can do anything because the alternative is that they take down multiple city blocks for hours...
Well, I know people who work in the power generation and distribution business in the midwest U.S. Arcs cause resets, too many resets, and the circuits are taken out and it takes serious human intervention to bring them back in. This costs time and money. I find it shocking that there are utilities that scrimp on a few links of insulator to lengthen the path to ground through the dust buildup so that they don't have periodic fault to ground or fault to phase events. Those can get expensive fast. Once again, if any area experiences more than a few of these events and the plant engineers don't schedule a fix on the next maint outage they should be fired. Dumping an 18.8 kV feeder sucks. Dumping a 46 kV feeder is a major pain. Dumping a 230kV trans line will inconvenience lots of customers and will cost a fortune to cycle and bring back up. A utility doesn't let that happen more than about two times before heads roll. About the only thing that would piss off the management worse would be doing something really stupid and getting a 600MW alternator kicked out of the grid and having to spin it back up and sync it back in.
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One of the main problems with underground cables is locating faults. Most faults are caused by water seeping into the cable via a damaged insulator. When enough water has seeped in, the cable shorts and blows the breaker. Unfortunatly, this also dries the cable out nicely, which means that testing for the fault becomes a problem. The best method for locating these faults is to switch bits of cable in and out, and narrow down which section it is, then dig it up.
And how do the insulators get damaged? One way that happens more than most people would admit is it gets clipped by someone digging up something else. Say you are digging up the gas pipe in the street. If you just nick the electricity cables insulation, would you tell your boss so he can get the electric company out to replace the cable, delaying your work by hours, or are you just going to throw some dirt over it, so no-one will be able to tell?
I have worked for 2 Electric companies, so I know a little about this.
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Ithink it shouldn't be to hard to design those tunnels in a way where you can use robots like in the sewage systems.
Really? The reality is that sewage work is still done by humans, not "robots". There's no way that a "robot" can dig up a street to replace a broken water main or sewer pipe, and the fibreglass inserts/patches are NOT a long-term fix when a pipe breaks.
Besides, you've overlooked the installation costs. It can easily be 100x more expensive to run a wire underground than overhead. Overhead - 2 cherry pickers, 5 guys, a few spools of wire, a day, and a couple of blocks are rewired (they just upgraded all the wiring on the street 2 blocks over last week - took 2 days because of the trees. On the other hand, 3 years ago they did a major upgrade along about 40 blocks - in one day - with a larger crew of cherry-pickers and support vehicles). Underground - backhoes, loaders, dump trucks, flatbed, concrete saw, gravel, conduit, manholes, manhole covers, asphalt repaving, cement mixer, sidewalk repair, 2 weeks, easily 30-40 people involved (gas, sewer, waterworks also have to be coordinated).
Then there are the transformer rooms (since you can't just hang them from a pole) - concrete pads, etc. Money money money.