Well, the ground return is Santa Monica Bay.
July 28, 2015 5:53 PM Subscribe
If you think finding a short in a light switch or lamp is your idea of fun, imagine having the time of your life with this little repair. You probably won't find much of the stuff you need at the Home Depot.
Misleading URL. I wanted to learn about how to engineer pornography.
posted by Faint of Butt at 6:03 PM on July 28, 2015 [1 favorite]
posted by Faint of Butt at 6:03 PM on July 28, 2015 [1 favorite]
A LiveJournal post from 13 years ago, copying a listserv post from 26 years ago. We live in interesting times.
posted by miyabo at 6:07 PM on July 28, 2015 [13 favorites]
posted by miyabo at 6:07 PM on July 28, 2015 [13 favorites]
Programmable plugs!
...is the name of my new band.
posted by Greg_Ace at 6:22 PM on July 28, 2015 [2 favorites]
...is the name of my new band.
posted by Greg_Ace at 6:22 PM on July 28, 2015 [2 favorites]
It is sort amazing to realize that the web is that old already.
Also, I read this with interest until it got down past the LN-2 and then my eyes started to glaze over and I had to stop.
posted by SLC Mom at 6:24 PM on July 28, 2015 [1 favorite]
Also, I read this with interest until it got down past the LN-2 and then my eyes started to glaze over and I had to stop.
posted by SLC Mom at 6:24 PM on July 28, 2015 [1 favorite]
A LiveJournal post from 13 years ago, copying a listserv post from 26 years ago
It's on a 13-year cycle.
posted by pjern at 6:25 PM on July 28, 2015 [9 favorites]
It's on a 13-year cycle.
posted by pjern at 6:25 PM on July 28, 2015 [9 favorites]
To complicate matters the cable consists of a copper center conductor living inside a 16 inch diameter pipe filled with a pressurized oil dielectric . Hundreds of thousands of gallons live in the entire length of pipe. Finding the fault was hard enough. But having found it they still have a serious problem. They can't afford to drain the whole pipeline - the old oil (contaminated by temporary storage) would have to be disposed of and replaced with new (pure) stuff which they claim takes months to order (in that volume). The cost of oil replacement would be gigantic given that it is special stuff. They also claimed the down time is costing the costing LA $13,000 per hour. How to fix it and fast?1989, huh?
. . .
Last night the DWP held a curbside chat to allay the neighborhood's fears that they were going to accidentally blow us all up. Apparently all the vapor clouds from all the LN-2 blowoff had caused a great deal of concern.
They probably should have been worrying about that old oil, which was very likely heavily contaminated by PCBs.
posted by jamjam at 6:28 PM on July 28, 2015
But we have seen this many times.
The last time it was in reddit, where the advocates of secrecy asked for this to be taken down, lest other swarthy immigrants used the information to cause a blackout.
Of course, I did a search using Google Maps. How would you go around finding those cables?
posted by kadmilos at 6:29 PM on July 28, 2015
The last time it was in reddit, where the advocates of secrecy asked for this to be taken down, lest other swarthy immigrants used the information to cause a blackout.
Of course, I did a search using Google Maps. How would you go around finding those cables?
posted by kadmilos at 6:29 PM on July 28, 2015
It's on a 13-year cycle.
A good ol' cicada repost
posted by bottlebrushtree at 6:32 PM on July 28, 2015 [7 favorites]
A good ol' cicada repost
posted by bottlebrushtree at 6:32 PM on July 28, 2015 [7 favorites]
screeching noises
PRINT --> OPEN PDF IN PREVIEWposted by snuffleupagus at 6:55 PM on July 28, 2015
I for one am glad this was posted! I love pylons and it's really cool to learn about other types of power transference systems!
posted by rebent at 6:58 PM on July 28, 2015
posted by rebent at 6:58 PM on July 28, 2015
Wouldn't it have been easier to run the power lines above ground?
posted by octothorpe at 7:08 PM on July 28, 2015
posted by octothorpe at 7:08 PM on July 28, 2015
The oil is pressurized to 200 psi. If it exploded it would obliterate entire neighborhoods and be an ecological disaster. I'm guessing being underground mitigates that scenario.
posted by Brocktoon at 7:19 PM on July 28, 2015
posted by Brocktoon at 7:19 PM on July 28, 2015
200 psi will in no circumstances ever obliterate entire neighborhoods.
If it wasn't underground, you wouldn't use the oil at all.
posted by kiltedtaco at 7:22 PM on July 28, 2015 [3 favorites]
If it wasn't underground, you wouldn't use the oil at all.
posted by kiltedtaco at 7:22 PM on July 28, 2015 [3 favorites]
The line is being worked on currently.
Brakes Put On Big Westside Power Line Project
(2010 Curbed LA story on proposed work on the Scattergood line delayed for EIR)
Scattergood-Olympic Transmission Line Project
(2014 LA Times story on project underway, with route map)
DWP page and project schedule
posted by snuffleupagus at 7:25 PM on July 28, 2015 [3 favorites]
Brakes Put On Big Westside Power Line Project
(2010 Curbed LA story on proposed work on the Scattergood line delayed for EIR)
Scattergood-Olympic Transmission Line Project
(2014 LA Times story on project underway, with route map)
DWP page and project schedule
posted by snuffleupagus at 7:25 PM on July 28, 2015 [3 favorites]
> Wouldn't it have been easier to run the power lines above ground?
If they were run above ground they'd be treated as extra high voltage high-tension lines (230 kV), and have to go up on tall pylons and building construction near/under them would be forbidden. Which, in NYC or southern California, would kill the project dead forever. That's potentially billions of dollars in real estate taken off the market for the sake of power line highways running over the landscape.
posted by ardgedee at 7:39 PM on July 28, 2015 [1 favorite]
If they were run above ground they'd be treated as extra high voltage high-tension lines (230 kV), and have to go up on tall pylons and building construction near/under them would be forbidden. Which, in NYC or southern California, would kill the project dead forever. That's potentially billions of dollars in real estate taken off the market for the sake of power line highways running over the landscape.
posted by ardgedee at 7:39 PM on July 28, 2015 [1 favorite]
If they were run above ground they'd be treated as extra high voltage high-tension lines (230 kV), and have to go up on tall pylons and building construction near/under them would be forbidden. Which, in NYC or southern California, would kill the project dead forever. That's potentially billions of dollars in real estate taken off the market for the sake of power line highways running over the landscape.
Just the eminent domain payments would be way into the hundreds of millions. Tens of thousands of jobs would have to be relocated.
Plus, you'd have to shut down the 8th busiest airport in the planet since you can't have giant pylons literally right in front the runway since the planes already almost fly over the power plant on take off as it is.
posted by sideshow at 7:47 PM on July 28, 2015 [1 favorite]
Just the eminent domain payments would be way into the hundreds of millions. Tens of thousands of jobs would have to be relocated.
Plus, you'd have to shut down the 8th busiest airport in the planet since you can't have giant pylons literally right in front the runway since the planes already almost fly over the power plant on take off as it is.
posted by sideshow at 7:47 PM on July 28, 2015 [1 favorite]
high voltage high-tension lines (230 kV)
"tension" is a synonym for "voltage" (and is actually the earlier usage). The redundant wording here implies it means something else (like mechanical tension).
posted by AstroGuy at 8:04 PM on July 28, 2015 [3 favorites]
"tension" is a synonym for "voltage" (and is actually the earlier usage). The redundant wording here implies it means something else (like mechanical tension).
posted by AstroGuy at 8:04 PM on July 28, 2015 [3 favorites]
200 psi will in no circumstances ever obliterate entire neighborhoods.
Yeah, but 100,000 gallons of oil might not be fun in your backyard at any pressure. (Ok, yeah, it can really only be at one pressure in your backyard)
posted by ctmf at 8:06 PM on July 28, 2015
Yeah, but 100,000 gallons of oil might not be fun in your backyard at any pressure. (Ok, yeah, it can really only be at one pressure in your backyard)
posted by ctmf at 8:06 PM on July 28, 2015
Sod jetpacks. I want my room-temperature superconductors.
Which were made in 2014, apparently, with the small problem that they only worked for a few microseconds. But then, they are deeply weird, even by deeply weird physics standards.
posted by Devonian at 8:13 PM on July 28, 2015 [1 favorite]
Which were made in 2014, apparently, with the small problem that they only worked for a few microseconds. But then, they are deeply weird, even by deeply weird physics standards.
posted by Devonian at 8:13 PM on July 28, 2015 [1 favorite]
If it wasn't underground, you wouldn't use the oil at all.
The oil is there for an interesting reason! The oil is an extremely good electrical insulator. It's not there because stray power would somehow leak out of the cable and into the ground or something. It's there because without the oil, the line would act like a giant capacitor with the copper as one side and the (fairly conductive) earth as the other side. All the energy would go into charging and discharging this capacitor 60 times per second, causing the entire to heat up and melt if engineers ever tried it, which they wouldn't. So the only way you can get away with putting a high voltage AC power line in wet dirt is by insulating it very, very well.
Above-ground lines don't have this problem because air is already a fairly good insulator.
Another way to fix this is to use DC instead of AC. But converters are expensive -- I don't know if they would be practical now, and they definitely weren't when this line was built.
posted by miyabo at 8:16 PM on July 28, 2015 [4 favorites]
The oil is there for an interesting reason! The oil is an extremely good electrical insulator. It's not there because stray power would somehow leak out of the cable and into the ground or something. It's there because without the oil, the line would act like a giant capacitor with the copper as one side and the (fairly conductive) earth as the other side. All the energy would go into charging and discharging this capacitor 60 times per second, causing the entire to heat up and melt if engineers ever tried it, which they wouldn't. So the only way you can get away with putting a high voltage AC power line in wet dirt is by insulating it very, very well.
Above-ground lines don't have this problem because air is already a fairly good insulator.
Another way to fix this is to use DC instead of AC. But converters are expensive -- I don't know if they would be practical now, and they definitely weren't when this line was built.
posted by miyabo at 8:16 PM on July 28, 2015 [4 favorites]
My intuition is telling me that the complicated design of the conductors is all about using the skin effect. Is that correct? Can anyone eleborate?
posted by Ivan Fyodorovich at 9:59 PM on July 28, 2015
posted by Ivan Fyodorovich at 9:59 PM on July 28, 2015
Worth it just for the reference to Bob Kerns, who is also good at telling stories.
posted by koeselitz at 10:39 PM on July 28, 2015
posted by koeselitz at 10:39 PM on July 28, 2015
The oil is there for an interesting reason! The oil is an extremely good electrical insulator. It's not there because stray power would somehow leak out of the cable and into the ground or something. It's there because without the oil, the line would act like a giant capacitor with the copper as one side and the (fairly conductive) earth as the other side. All the energy would go into charging and discharging this capacitor 60 times per second, causing the entire to heat up and melt if engineers ever tried it, which they wouldn't. So the only way you can get away with putting a high voltage AC power line in wet dirt is by insulating it very, very well.Huh? A capacitor, almost by definition, is a pair of conductors separated by an extremely good insulator. Capacitance is affected by, amongst other things, the dielectric strength (k) of the insulator - as k increases, so does the capacitance. Dry air at STP has a k of 1. cable/transformer insulating oils have a k of 2.2 or so.
Congratulations - by adding oil, you've just made an even bigger capacitor!
No, the oil is there mostly because it's (a) a better electrical insulator than air, (b) a better heat conductor than air, (c) is relatively stable, and (d) excludes moisture.
The key with feeders like that is (a) all in the bundling, and (b) the balance between the current flow in each phase. Spiral winding the insulated conductors reduces losses outside the bundle ('loss' currents are induced into the adjacent phases, rather than the surrounding pipework/soil/whatever). And correct balancing of the phases ensures very little current actually flows though the 'earth return' circuit (in this case, the soil & Santa Monica Bay).
Mind you, "very little" in a 180MVA system can still be quite a bit, and you still need to design for large fault currents. Hence the large 'anchor' electrodes mentioned…
Not skin effect either; at least, not much. Skin depth @ 60Hz is something like 8 or 9mm. When bundled, the EM field from current in one conductor will 'push' the conductive region a bit deeper than that in adjacent conductors - but still, there's not much point going any thicker than an inch or so. No, the construction is simply to ensure that all the conductors are insulated from each other, retain their bundling to minimise losses to the outside, and don't move (due to uneven heating, self-induced magnetic fields, etc) during operation.
posted by Pinback at 10:50 PM on July 28, 2015 [12 favorites]
Pinback did a good job of explaining. The oil is for insulation. It fills all the voids in the paper insulation so that there are no discontinuities in the electric field within the insulation that could cause a breakdown. The oil also conducts heat away much better than air.
For a 1-inch cable, as in this instance, the skin effect is minimal. A larger cable would not be able to carry much more current because it would be carried in the outer half inch of radius. This is one of the limitations of high voltage AC cables. DC cables on the other hand can be made much bigger and carry more current.
The more important factor in this case, since the conductor is only 1 inch, is the proximity effect. It means that current tends to concentrate nearest to the adjacent phase cable. This is mitigated by spacing the three conductors farther apart from each other. The 1-inch conductor is wrapped with paper insulation to form a 3-inch insulated conductor. This large diameter not only provides insulation but more importantly keeps the conductors spaced from each other to reduce the proximity effect.
Then each conductor is wrapped in a copper sheath. This layer forms an electrical shield to prevent electric fields outside of the conductor, much like the shielding on a data cable. The copper shield is typically earth grounded at one end to eliminate voltages from capacitive coupling from the inner conductor. Finally the cable may be wrapped with a spiral bronze wire that reduces the friction of pulling the cable through the steel pipe and also protects the copper shield.
This is an older style AC cable going back the the 1920s right up through the 1980s, although still installed occasionally . Newer cables typically have cross linked polyethylene (XLPE) plastic insulation instead of paper and oil.
If you are interested, there is a picture of this type of cable system in a pipe on page 10 of this 2 MB PDF.
posted by JackFlash at 12:21 AM on July 29, 2015 [9 favorites]
For a 1-inch cable, as in this instance, the skin effect is minimal. A larger cable would not be able to carry much more current because it would be carried in the outer half inch of radius. This is one of the limitations of high voltage AC cables. DC cables on the other hand can be made much bigger and carry more current.
The more important factor in this case, since the conductor is only 1 inch, is the proximity effect. It means that current tends to concentrate nearest to the adjacent phase cable. This is mitigated by spacing the three conductors farther apart from each other. The 1-inch conductor is wrapped with paper insulation to form a 3-inch insulated conductor. This large diameter not only provides insulation but more importantly keeps the conductors spaced from each other to reduce the proximity effect.
Then each conductor is wrapped in a copper sheath. This layer forms an electrical shield to prevent electric fields outside of the conductor, much like the shielding on a data cable. The copper shield is typically earth grounded at one end to eliminate voltages from capacitive coupling from the inner conductor. Finally the cable may be wrapped with a spiral bronze wire that reduces the friction of pulling the cable through the steel pipe and also protects the copper shield.
This is an older style AC cable going back the the 1920s right up through the 1980s, although still installed occasionally . Newer cables typically have cross linked polyethylene (XLPE) plastic insulation instead of paper and oil.
If you are interested, there is a picture of this type of cable system in a pipe on page 10 of this 2 MB PDF.
posted by JackFlash at 12:21 AM on July 29, 2015 [9 favorites]
Field Report, Agent Kay, 1989-10-20 18:30
Subject Beta returned with further questions re: nitrogen outgassing. Had to elaborate on power transmission cover story. Luckily had a small tin of sewing machine oil on hand. Essential we now supply each location with same to maintain cover.
Maintaining cover is starting to take more time than the core operation. Must query Zed re: progress on neuralyzer.
End Report
TOP SECRET: EYES ONLY
posted by oheso at 4:28 AM on July 29, 2015 [8 favorites]
Subject Beta returned with further questions re: nitrogen outgassing. Had to elaborate on power transmission cover story. Luckily had a small tin of sewing machine oil on hand. Essential we now supply each location with same to maintain cover.
Maintaining cover is starting to take more time than the core operation. Must query Zed re: progress on neuralyzer.
End Report
TOP SECRET: EYES ONLY
posted by oheso at 4:28 AM on July 29, 2015 [8 favorites]
This is so cool. Capping the oil by freezing it with LN2. Thumping to find the failure points. And knowing that it's costing $13k an hour. Much respect to those engineers.
posted by mbd1mbd1 at 7:39 AM on July 29, 2015 [1 favorite]
posted by mbd1mbd1 at 7:39 AM on July 29, 2015 [1 favorite]
This is my old neighborhood in LA, (Playa Del Rey, specifically the Jungle in case any of my old neighbors are on here). I can think of a few good reasons for it to be underground, namely that (1) this cuts across a salt marsh that, while safe for now, developers have been aching to get at for decades, (2) there's underground pressurized gas storage within exploding range (here), and (3) people in LA like to imagine the oily, dirty infrastructure doesn't exist so everything is either clad in fake building facades or hidden unless it's an overhead power line and don't you mess with those.
posted by late afternoon dreaming hotel at 12:11 PM on July 29, 2015
posted by late afternoon dreaming hotel at 12:11 PM on July 29, 2015
I would have suggested TDR, but I see that didn't work.
I was wondering how that would show up with this kind of 'wire'.
posted by MtDewd at 2:41 PM on July 29, 2015
I was wondering how that would show up with this kind of 'wire'.
posted by MtDewd at 2:41 PM on July 29, 2015
Another way to fix this is to use DC instead of AC.
It's funny you mention that. It turns out that in the course of being wrong in almost all squabbles with Tesla, Edison was accidentally correct about the benefits of DC for long-distance transmission. Even a stopped clock is right twice a day, right?
It is especially useful for underwater transmission, and for transferring or balancing power between unsynchronized AC systems (the latter being better known to me as the Kyoto/Tokyo problem).
This concludes the only occasion where I know more about electricity than any of y'all.
posted by ivan ivanych samovar at 3:30 PM on July 29, 2015 [1 favorite]
It's funny you mention that. It turns out that in the course of being wrong in almost all squabbles with Tesla, Edison was accidentally correct about the benefits of DC for long-distance transmission. Even a stopped clock is right twice a day, right?
It is especially useful for underwater transmission, and for transferring or balancing power between unsynchronized AC systems (the latter being better known to me as the Kyoto/Tokyo problem).
This concludes the only occasion where I know more about electricity than any of y'all.
posted by ivan ivanych samovar at 3:30 PM on July 29, 2015 [1 favorite]
You wouldn't use HVDC for the link in this case since it is only 10 miles long. HVDC is only cost effective for very long transmission lines, typically more than 400 miles, and somewhat less for undersea cables.
The conversion between AC and DC requires some very expensive and highly technical equipment, and conversion plants on both ends the size of a small factory which you can see here. This is in addition to enormous air conditioning systems to remove the heat losses.
AC step-up and step-down transformers are quite simple and much more energy efficient than HVDC converters. HVDC in some cases can make up for this greater expense and conversion loss by having lower losses over very long distances.
Anything within the confines of, say, the city of New York, then Tesla was right. AC distribution works better.
posted by JackFlash at 5:09 PM on July 29, 2015 [1 favorite]
The conversion between AC and DC requires some very expensive and highly technical equipment, and conversion plants on both ends the size of a small factory which you can see here. This is in addition to enormous air conditioning systems to remove the heat losses.
AC step-up and step-down transformers are quite simple and much more energy efficient than HVDC converters. HVDC in some cases can make up for this greater expense and conversion loss by having lower losses over very long distances.
Anything within the confines of, say, the city of New York, then Tesla was right. AC distribution works better.
posted by JackFlash at 5:09 PM on July 29, 2015 [1 favorite]
miyabo: "Above-ground lines don't have this problem because air is already a fairly good insulator. "
Compared to most anything else we consider an insulator it's pretty poor actually (about a MV/m). The typical plastic insulation protecting the wires in your house has a rating of 10-100x that for example. It's big advantage is that it is is literally free as air.
posted by Mitheral at 9:12 PM on July 30, 2015
Compared to most anything else we consider an insulator it's pretty poor actually (about a MV/m). The typical plastic insulation protecting the wires in your house has a rating of 10-100x that for example. It's big advantage is that it is is literally free as air.
posted by Mitheral at 9:12 PM on July 30, 2015
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This thread has been archived and is closed to new comments
Does this random photo thing of his still work? Exterminate All Rational Thought.
Yep.
(Potentially NSFW.)
posted by notyou at 5:59 PM on July 28, 2015 [1 favorite]