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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?
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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actually this is the big point. Power companies can massively undersize wires that are traveling in free air.
Three conductors in free air 15 feet off the ground the power companies can run a #2 sized cable for 200 amps. Yet that same wire underground needs to be 4/0 or 250 MCM which is several times larger.
The cost of goods to run lines over head is considerable less even if you take into account storms trashing it. Just from a dollar point of view you can competely rebuild a surface grid two or three times for the cost of doing it once underground. Digging costs that much more. Digging near roads is even worse.
I think it makes long term sense to go underground but I do see the cost advantages of going above. Plus the union can hire more people.
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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
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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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