On a related note, power distribution in the South
Posted by Heading Out on January 31, 2006 - 12:04pm
To follow up on a discussion we held just after the Hurricanes, but which has slipped my memory as to when, there is a press release from Florida Power and Light, talking about the need to harden the power distribution system. This is fairly relevant since the loss of power to refineries played a part in the length of time that they were off-line.
But apropos our discussion I thought I would just add a little quote:
Investing in Underground Conversions - FPL is committed to increasing its underground facilities. More than 37 percent of its current system is already underground. FPL will further its commitment by offering to invest 25 percent of the cost of converting overhead lines to underground for local government-sponsored conversions. By this action FPL is encouraging local governments to take the necessary steps to invest in conversion.In addition, FPL will enhance existing efforts with local governments to strongly encourage ordinances requiring developers to provide underground electrical service for all new subdivisions, developments and projects. Furthermore, FPL will support legislation that would require similar action statewide. The company will also support efforts by municipalities to obtain federal or state funding to assist in underground conversions.
“If kindness and comfort are, as I suspect, the results of an energy surplus, then, as the supply contracts, we could be expected to start fighting once again like cats in a sack.”
—George Monbiot
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The hurricances have shifted the economics towards undergrounding.
Here in California. undergrounding fees are built into the electric rates. Each communitity then has an annual allocation of funds which they can build up for big projects. They local government pays a big chunk of the total project costs but is aided by the fund.
For new development, many communities will zone it for underground utilities during the construction phase so that the costs are built into the price of the land.
I've heard a lot of complaining about overhead wires and transmission lines. Sure, they are nicer but SOMEBODY has to pay 10X as much for that niceness.
Any thoughts
Robert NW ohio
The overhead electrical lines were not expensive. They didn't need to be protected like underground lines would have. It was a rat's nest, with bare wires running everywhere. There was at least one gruesome incident where someone who touched a wire was electrocuted. His body hung above the streets, caught in the tangled wires for hours. Rescuers were unable to get him down for fear of being electrocuted themselves.
He was definitely bootstrapping his operation with venture capital from J.P. Morgan (one of his first customers, on Wall Street.)
Overhead was cheaper and easier although he had underground too since his system was low voltage DC but it used a lot of copper. Nikola Tesla dug ditches for Edison for a while.
One problem is that underground New York was owned by the Astors. Putting stuff on the surface was one thing but burying wires required paying another set of landlords!
When Westinghouse came up with alternating current, its big technical advantage was high voltage which meant longer transmission and much less copper use. Voltage far outran undergrounding technologies. To this day underground transmission technology lags overhead. For example, I know of no 1,000,000 volt underground line while such voltages overhead are commonplace.
It has long been a US policy preference for cheap energy and cheap electricity. Overhead is so much cheaper than undergrounding.
The first power cables I know about were insulated with oil filled paper made water tight with an extruded layer of lead and then protected with a wrapping of jute rope and steel bands. This is a robust technology that still is used for some cables. But it must have been expensive compared with the same ammount of copper or less in free air with some porcelean, steel and poles.
Did you realy electrifie after you built the pipelines??? Should it not have been the other way around?
I am aware of the cost to run 600 MW just over one km out (in a tunnel) from an underground hydroelectric power station and it cost over a million. In another case, drilling under the Mississippi River for a HV line cost several million.
Putting most high voltage lines underground is just price prohibitive. Induced current on the surface would cause problems as well.
Oil refinery power requirements typically require high voltage connections.
The step up and step down is made in transformers as AC.
There might be a small start of a kind of HVDC grid within in Sweden since a fairly long 400 kV AC line intended to add redundance to southern Sweden might get built as HVDC. I think this would be a good idea for technology demonstration but a bad idea for added redundacy per $ since a traditional 400 kV AC line easily and fairly cheaply can be connected to older lines crossing it between the endpoints giving extra redundancy. On the other hand it would be built with newer technology making it possible for it to convert active power to reactive power wich southern Sweden need more of.
The limit for AC thru cables is the parallell capacitance. Basically when the cable gets too long all the current fed into it charges and discharges this capacitance and no power is left to deliver in the other end.
If one would build a complete grid from scratch in the near future it might make sence to use +/- 10 kV DC or so to each and every house allowing cables with very little metal and losses and then step down the voltage. This will make more and more sence as power semiconductors are developed further. It has actually been sugested by some innovators in Sweden as an economical way to build a parallell redundant emergency power grid connected to centraliced accumulators and emergency diesels instead of every other company buing their own set that often is too small and badly maintained. On the other hand it would still be sensitive to lightening. And for the apocalypticons, EMP. ;)
Their overhead HV wires are over 50% steel, rest aluminum. Highest % in the world. 110 mph winds with 1 inch coated ice on wires.
From a servicing standpoint, overhead lines are far easier to observe, inspect and repair than underground lines. I discussed this and other pros and cons with a line engineer with SCE. According to the engineer, his crews prefer servicing and troubleshooting overhead lines because the entire portion is visible. If there are issues with an undergrounded circuit between transformers or other equipment, they pretty much have to replace the entire segment.
Longer term, underground equipment and lines do have usable lifespans. Which means there will come a point in the future where these lines WILL have to be replaced. How long that lifespan is is dependent on the quality of the equipment and wires as well as how much load those circuits handle. According to the engineer, early undergrounding equipment lifespans were approximately 30 years, give or take. Most of what goes underground today will last 50 years or so, provided the electrical load remains at the rated capacity. 50 years is a pretty good length of time but as we know simply putting off a problem (the eventual need to replace the lines) into the future does not mean it will be addressed (or could be addressed) when that time comes. Repair and or replacement of undergrounded lines will almost certainly be more difficult to utility companies than the original undergrounding was (mostly performed by the developers).
And that assumes that the raw material/specialized equipment is readily available and affordable.
On a personal note, I lived in a subdivision (in Virginia) that was undergrounded in the early 60's with lines with a 30 year lifespan. As expected by the late 80's the system was showing its age. We would lose power every time it would rain more than one inch. The utility could never locate the problematic section so after a year or so of undependable service they replaced the entire distribution section.
Makes you wonder which method is better in the long term.
Stssgabs100
We were placing a traffic signal pole at an intersection for a 'hurry up' job. The DOT rep brought the utility companies together on site and said, "We are drilling here (pointing to the ground) Monday with a 48" auger down to 22'. Is anyone in the way? Yes or No." An old worker from the local water company said there might be a problem because he didn't remember the water line being where it was marked (in the nearby ditch). So they dug it up. The 8" water line made a jog in the middle of the sidestreet but the locate guys didn't pick up on it because of the high water table. Our pole foundation was actually closer to the locate markers, by 10', than the water line was.
Next: Fiber Optic contractors for the telephone companies are notorious for putting a couple big loops (10+') of fiber at the end of a run. They just throw it out to the side and bury it. The locates come along, and miss the big loop to the side and go to the junction box. I know power would be in conduit, but 'stuff happens'.
The best underground utility locator in the world: a Backhoe.
No undergound AC near pipelines please. It not real great inducing electrical currents in my pipelines. Causes hell with corrosion protection.
One trouble with undergound electrical cables is the prarie dogs and other underground rodents that like to munch on the cable coatings.. at least until they bite through to the wire. Another one is ... ants. Ants like those warm underground areas around the cables where they connect to substations. They occasionally short them out with thousands of their little bodies.
Aside: Thomas Edison was undoubtedly a great man, but he didn't "get it" right all the time either, my favorite quote by Thomas Edison, "There's no future in AC."