Repairing Underground Power Cables Is Nearly Impossible
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- เผยแพร่เมื่อ 2 พ.ค. 2024
- In 1989, this story about an underground electrical transmission line spread across the early internet like wildfire. It had a big impact on me as a kid, and I wanted to share it with you! I think the Scattergood-Olympic transmission line is probably LA's most famous power line, although it has now been replaced with a more modern line since 2018.
Original story here: www.jwz.org/blog/2002/11/engi...
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Thanks to Tom McMahon for letting me repurpose his original story and jwz for preserving it on his blog.
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GREAT video. However, I find the title slightly misleading since the problem as described (to the best of my understanding) is not only specific to underground *transmission* lines, but to lines with a very specific type of cable. If you're up to doing a follow-up video, more insight into the differences between the old and the new lines would be interesting.
I really really love the series of videos where you explain what happened in a notable engineering disaster. I cant wait for more of them!
I've got an interesting thing i'd want to be cleared.
Bycicle lanes. Modern day bycicle lanes. I think a good way to start would be not just bike's channel.
If you woule consider my suggestion i would be extremely gratefull!
Hi Brady, could use do video of perpetual motion theory.
Great video, thanks. You have yourself another sub!
Singapore has a rather interesting (though experimental) solution for this, instead of buried lines that need to be dug up each time for repairs and modifications, a huge tunnel is dug (similar to train/vehicle tunnels so they can be easily accessed even by humans and machines), the lines are laid inside the tunnel which can be easily accessed without any digging up, while still having the benefits of not being exposed to weather
That's probably extremely expensive in comparison.
not only singapoore.
I think London has it aswell, where power and sewage in newer parts are combined into accesstunnels and the diferent pipes run inside a tunnel...
And I believe in Switzerland it is also in some parts done...
@@fatweeb1545 only short term... and if you combined every utility service into the tunnel, ease of access and reparability would probably be profitable quite quickly
@@BlackDragonWitheHawk quite quickly? You mean 40-50 years? You're comparing the price of burying cables and occasional meintenance to digging a friggin tunnel.
@@BlackDragonWitheHawk Are you sure it's feasible or smart to run "all utilities" -- potable water, storm sewer, sanitary sewer, high speed fiber-optic, high voltage electric and perhaps more -- in the same "big pipe" or bore hole.....? 🤔 I'm skeptical and unlikely to invest!
Literally after the first Practical Engineering video I saw, I wanted to be an engineer. I've always loved science, maths etc.. But Grady, you've set me on my true path. I will never be able to thank you enough!
I thought I wanted to be an engineer, till I put in 2 years...
After that, being practical I knew I needed a job, and ended up in medical imaging, later specializing in MRI.
For years it bothered me that my engineering schooling had been a waste ..
20 years later I'm working at a university with roles in MR safety, MRI research, and imaging protocol optimization.
My engineering background helped me understand MRI safety implitations, RF absorbtion of implants and foreign bodies, MR physics, dielectric effects and electromagnetic wave propagation through tissues, implants, etc.
I advise physicians on patient safety for off label imaging of implants and foreign bodies..
My schooling and what I learned was definitely not a waste.
Good luck with engineering, and apply it to everything you do :)
When you get where you want to be, take him out for a beer. :)
I always wanted to be an engineer, so I earned an electrical engineering degree. Sadly, then I got a job. 30 years later, I think it would have been nice to actually had done some engineering. Work was nothing like what I learned at uni.
@@Unsensitive I build MRI's for a living (for the last 2 years anyways) and I'd LOVE to get more into the engineering side of it, Especially after seeing how they are built.
I honestly feel like the place I work at is Screwing up. Bad. But because I dont have 12 years of college under my belt they tend not to listen to things I have to say/questions I ask... Kinda sad really...
As someone that has always had an interest in engineering but went for the "hands on" approach I offer this bit of advice, Get Your Hands Dirty.
Spend 1-3 years in a weld/machining shop, or join up on a construction crew and actually get some real hands on experience building things in the field.
Its not going to be easy, but it will be worth it in the long run.
Engineers: "We invented new cool technology!"
Also engineers: "..And now we have to invent 20 other new technologies to maintain it"
This is a bureaucratic issue with the uninterrupted power supply. Blame a shareholder or a pencil pusher for this. I am an engineer and im guessing dumb issues like this stem from cutting costs and contracts and such. Because instead of quantity or quality you get too few too little.
@@cactusmann5542 You might be right. Just asking: Is the grid system and such private or state owned in California?
@Lazys The Dank Engineer Some Americans might call me a communist but I firmly believe that certain infrastructure shouldn't be private owned such as water, electricity etc.
Capitalism: yes…good. Exactly as I foresaw.
@@NM-ev7pu Nothing but entertainment and luxury items should be privately owned.
I work for lane construction company in Austin, I love every second of this guy's videos, makes me feel less alone in this large construction world. We're important but some ppl don't realize. This man is doing good work love this guy
May God bless you. Thank you for your service.
When you got to having to open the pipe, first thing that came to mind was 'freeze seals'. We used both LN2 and Freon-based freeze-seals during maintenance outages at power plants to avoid having to completely drain key systems. Works great with water since water expands when it forms ice. Didn't know you could do that with oil, learned something new today. Thanks. :)
Same, I did one last year while the plant was still online, 2500psi held back by a 4" freeze seal. It was honestly amazing.
Would you have to worry about the expansion of the ice as it freezes? Even if it wouldn't break the pipe you would have to be concerned about the possibility of stretching/weakening of the material, at least if the fluid is normally high pressure.
@@jwmoffat I was wondering the same thing, why it doesn't do more harm than good.
@@rsethc probably because it has space to expand, the water might be pressurised but ice makes a ton of pressure.
@@jwmoffat Freezing a pipe filled with water would be tricky. But water is the only liquid that expands when it freezes, everything else, including oil, contracts. As the oil freezes and contracts, I would presume that more oil fills the space until there is a full width plug.
I work for a utility in the Northeast and we did some work like that on a 115 kV line that travels underneath the city. Very interesting work especially when you consider that the cable is insulated with paper and oil. Solid dielectric cable is quite a bit less labor intensive. If you feel like continuing on in this electrical infrastructure series, maybe a video about how the cable is constructed would be interesting to your viewers. Especially the differences between oil-filled cable, pilc cable, and solid dielectric cable.
Was the solid dielectric cable available in 1975?
I read an article a few months back talking of a theoretical cable to be run from northern australia to singapore, to transport solar power, one of the biggest challanges was how to insulate it at the voltages needed as the voltage useable drastically altered the viability of the entire project.
@@RonJohn63 No, only ones available were paper insulated, with a choice of either oil impregnation or sulphur hexaflouride as pressurising gas. The development of a reliable solid dielectric cable, plus the oft ignored method of joining it without introducing a step in voltage gradient, which is generally where the cable fails, was a big improvement.
By me locally they have been laying more solid dielectric cabling to replace older cables as they are ageing out, getting rid of the oil impregnated 66kV cables and going to solid dielectric 132 kV rated cable, though they are only being run at 66kV, as the load is not that large they need to swap out transformers. Doing the expensive part of digging, jointing and burying the new cables in the existing rights of way is saving money, as the major cost is the trench, the cable itself is not as big a part. Yes it comes on 200m rolls, and they bury 3 at a time, staggering the joints so as to keep within the trench opening. All aluminium cable as well, they are making a good chunk of the cost back by digging out the old cables, put in in the 1950's, as those are copper core cables.
Same for overhead distribution wire, the scrap cost of the copper taken down pays for the new aluminium bundle cables that goes up to replace it, and as a bonus they also tend to replace street light lamps on the pole, as they take the shorting plug out, and replace it with a photocell, as the ABC cable does not come with a group street light core. Gets rid of the dead lamps, though the cyclers still stay there.
Yes
@@SeanBZA has there been any problems or repairs needed with this new cable..?
I was working for LADWP when this line was installed, knew most of those working on the line. It ran close to my house so I would visit with them when I could. I also worked for the Generation section and was on the startup crew for Scattergood Unit 3 which this line was built for. Great video.
I'm a graphic designer & illustrator with no business getting my nose into this side of youtube but I find my self completely enamored with all of this complex engineering, I'm speechless and in awe of the great minds that created all of this, literally you guys keep the modern world together, and this video is magnificent, thanks for the effort of making it look so simple for us simpler folks ❤️❤️❤️
don't pay attention to the fact that they themselves (the psychopaths running the planet for their profit and psychopathic pleasure) announced long ago that they can make nuclear reactors small enough to be built in factories and delivered on trucks, eliminating the need for a complicated network with everybody depending on everybody else.
Of course then they couldn't knock us all off line and say sorry, it's just too hard to fix while they kill many or most of us.
How do you feel about A.I. taking your job?
@@ryshellso526 Just my two cents, but I feel like it’s going to be like when photoshop came out. We thought that it was going to destroy the photography industry, but it actually turned out to be a huge benefit.
As a water engineer I’ve come across these oil filled electrical cables a number of times. The asset owners have always been incredibly nervous about us working near these lines and now I know why! Thanks for the awesome vids, very informative.
Same, pipeline engineer here for drinking water and district heating. Theres 2 different variants from late 50's and early 60s: oil pressure and paper-lead cables. I always sigh when i encounter them because they lead to extensive discussions with the owner.
That oil is also highly flammable. Break those lines, and everyone is going to have a very bad day
@@michaelkincaid9582 If they fail underground they don't normally catch on fire. They quickly consume the available oxygen around them.
I worked Trouble at LADWP. A 230kV Cable would make an explosion you wouldn’t want to be around. There are videos about 35kV cables exploding that are bad enough.
@@RobertsIslandLivingAdventures
Worked those same lines 34.5kv and 138kv out of Hollywood.
When I lived in Denver we built a high voltage channel. It was the smartest engineering I have ever seen. We dug a trench and placed a metal tube that was coated in a really thick non conductive poly liner. Workers could walk through the tunnel and there was even a track system for a power feed system to run new power lines through it. The power lines were mounted to the sides of the chamber with an ingenious clamping system and the system was built so they never had to dig it up because they could inspect and even change out the mains without ever disturbing anyone.
@@steveperreira5850 In London and other UK cities from way way back, mid C19th at least, many utilities were houses in 'cable run's', brick lined cut + cover tunnels that run down the centre of many roads, housing originally drinking water, house gas, but later domestic electricity supply and telephone lines. Generally around 5-7' diameter with cast iron racking on either side so you can slide off and inspect/replace each utility without disturbing the others.
Unfortunately after 150+ years of service, many of the lines are wound around each other and are in a bit of a mess. Still easier than digging up the street all the time though.
@@faster4tec St Paul Minnesota, even a younger city, sits on a sandstone bluff, so it was super easy to carve out raw tunnels. Hundreds of them, layered at different depths. Nicknamed the Labyrinth by locals. I snuck down there once and saw what I believed to be a moonshining bathtub in an abandoned section.
Where at in Denver is this located?
@@BVonBuescher It was just outside of a sub division development we was building just south of Highlands ranch and our part ended right at the state park, dont recall the name of it but from what I know the Army Corp picked it up from where we ended and went through the park somewhere across (or in front of) the dam. Dont know where it was coming from or where it went beyond our contract though? It looked like they intended running it up the entire western corridor of Denver.
@@faster4tec Yea this system they ran some sort of neoprene rubber tubing through it, inflated it and then injected steam to expand and cure it to the insides of the pipe. The pipe came in 12 foot sections and was placed and welded together and the outside of the pipe was this super thick rubber like material. They said it had a life expectancy of 10,000 years and said if any of the inner lining went bad they had repair kits like those for rubber rafts that they could repair it with. Very ingenious system for sure and super heavy duty!
I went to school for electrical engineering with a focus in utility technologies. I currently work for one of the largest electrical utilities in the north east (US).
I have to applaud this video!! Your description and delivery of electrical infrastructure was incredibly impressive. Too often when people try to explain things with simplicity people either in accurately describe it or leave out key/fundamental information. Not only was your description simple for ordinary folks to understand it perfectly described the principles. Bravo!!!
Lastly I recently found your page and have watched around a dozen videos. Your content, research and delivery is nothing short of phenomenal. I LOVE your videos. Clear concise and loaded with interesting information presented in a attention grabbing format.
Thanks for your work! I’ll be a lifetime subscriber for sure
Practical Engineering and Mentour Pilot are possibly the two greatest channels on youtube.
Thank you so much for your scientific insights, educated tips, fascinating stories and general wisdom you spill among us.
I never even considered high voltage lines underground... literally next to ground! I love engineering problems like this. Liquid nitrogen to hold back pressured oil? What a fascinating problem to work on. Thank you for sharing this story.
wait til you hear about the internet underwater!
@@bermchasin undersea cables are fascinating. The undersea fiber optic cables are so amazing. I really like the story about Cyrus Field laying the first undersea telegraph cables too. I can't believe he managed to keep getting the ridiculous amount of funding for such an immense feat of engineering as it experienced so many problems and failed over and over and over again then when he finally managed to get a cable laid it hardly even worked and failed straight away and he still did it again.
The the contingency plans were cool :3 and the updated cables was nice :3
Yes, it’s all super clever
Now it makes sense why they don't just go burying all the power lines everywhere.
That map at 12:42 sent me out of my chair. The replacement cable project was completed in 2018, right when I was in college. lived about a quarter mile away from my college, LMU, and the road between my apartment and LMU was Lincoln Blvd. right along the cable replacement route. That project caused traffic for YEARS. For some reason, I never had the inclination to look up what it was, I just let myself falsely believe they were repaving the same stretch of road for months and months on end.
The LADWP sent me a slice of the new cable in honor of this original 1989 posting. Sitting right here in my office.
Much of the work was the replacement of conduit and vaults for the cable. The newer cable is larger in diameter than the old requiring replacement of the conduit. After that was completed, LADWP had to then pull in the new cable and splice the cable. The splicing technique for these line is quite extraordinary. LADWP had a crew from Korea that manufactured the cable to perform the splicing. It was an amazing operation.
I love it when there's a personal connection. Also, GO LIONS! 🦁💯
One of my favorite things I learned about it my engineering classes was time-domain reflectometry! I think its really fascinating how you can send a pulse down a conductor and receive the reflection to determine roughly where a break is. Its one of the things I actually still think about often when I hear of an outage somewhere. I think "cool, I know how they might actually find the fault!" Not saying I was actually any good at it in school, just thought the concept was really neat.
Time-domain reflectometer wiki:
en.wikipedia.org/wiki/Time-domain_reflectometer
I build power stations and have had two separate faults on 33 kV grid connections. Tdr was used by the distribution network operator on both occasions, it is imperfect, but can definitely narrow the issue down. Faults are always due to bad workmanship of joints. Always.
@@Tadesan it’s due to a lack of competence rather than cost really in the U.K. at least. The cost difference between a good jointer and a bad jointer is not material in the cost of major HV works. We now insist on having the CV of the jointer which puts off the “wannabes”.
Yeah its awesome.
TDR to find cable faults but the old timers I worked with didn't have TDRs. They used a breakdown set and then sent tone out on the line. I guess a lot trouble was moisture getting into the lines.
I lived in Scottsdale, AZ for 30 years, where almost all lines (both transmission and distribution) were buried underground for aesthetic reasons. I had NO IDEA I was walking around with 200PSI of heated oil underneath my feet, that is WILD.
Heh, weird to come across this on TH-cam - I'm an electrical engineer with expertise in HV cables, and I performed a forensic analysis on a fault on this particular circuit in the early 2000s. I have to say you did a decent job describing the story and offering the world a bit of insight into strange and esoteric business of high voltage cables.
Cool. Do you know what's up with the old cable? That "can be used as backup"? Does that mean it's still being actively pressurized??
@@xamishia I haven't been involved here for a long time but knowing these systems, that's what it would mean, yes, though possibly a reduced level (there would be pros and cons to that). They would be maintaining the pumping plants and monitoring gear, and any corrosion protection systems.
@@packratty Thanks kindly!
As an electrical engineer, that formerly worked for a thumper,TDR,hipot manufacturer, it's nice to hear recognition that underground fault location is half art, half science. And yeah, he did a pretty good job describing it!
Hey, Jody! This showed up on my feed as well! I guess the youtube algorithm is pretty good at finding the cable system issue root cause analysis people :)
This is such great insight into what we so often take for granted. The engineering challenges that learned professionals undertake every day continues to astound me.
High school math problems have nothing on this.
I was just thinking this too, non-engineers like me always just complain; "god damn it, the power's out again" "can these guys stop working for one day?!" "Oh great.. another street closed off". Completely ignoring the fucking wonders that happened for those luxuries to be there in the first place. Same with logistics tbh.
No, here we have a pure example of how somebody just came out with the most complex and expensive way to do the job. Like intentionally, like to scratch your itching right ear with your left foot's toe. Was it necessary to go this way, having at the time high voltage plastic-insulated cables with perfect quality? Guess what: It wasn't.
Holy crap, I remember reading this when I was a little kid! Incidentally, it did inspire me and I ended up becoming an electrician.
Wild stuff. When someone designed the oil-filled pressurized conduit, did they design the method of fixing it, too… or did that come later when things started to break?
This was adapted from high power radio transmission from transmitter to tower
Power are high up to reduce losses of transmitting power to the ground. There is a calculus to figure loss to ground vs tower height.
hell no, they will call up automobile engineers to fix the issue. gotta take out 30 parts to replace one $30 part
@@nickgibb4687 Ah! You've seen the video how to replace a Honda CRF250X carburetor. Applicable.
It was state of the art at the time. The biggest problem wasn't fixing leaks or breaks (easily enough to freeze oil plugs on either side of a problem), but to control voltage when the cable was lightly loaded.
And to think regulators and the public want to have the state investor-owned utilities (PG&G, SCE, and SDG&E) to run hundreds of miles of buried transmission.
There’s always this moment, usually gradual, but a moment where channels on TH-cam seem to cross a threshold, I never notice until maybe 2 or 3 vids after but I realize that the creator has hit a point where each video just feels like a massive jump in quality, as if they’ve figured out how to put more than 100% of their effort into every video they make, and each one just blows me away. I’m very sure that Practical Engineering is far past that threshold now and I didn’t have a clue until right now. I can’t wait to be blown away again!
Um wat.. his videos have been the same good quality for the last year+.
@@Merker367 You didn't read what they said, didn't you?
@@Merker367 that’s why I said 100%, they were already amazing, but they just keep getting better at a rate I can barely keep up with, it’s one of the joys of being in the audience instead of a creator for me, I get to watch creators I enjoy skyrocket to levels of quality that surpass content you’d usually pay for
After the last video I was signing up for crane operator courses!
He broke his limiter.
I designed a moderately elaborate earth retention system with many ground anchors close to a pipe-type cable (and several high-voltage tower foundations) several years back. The record drawings furnished by the utility (our client) only indicated an oil-filled steel pipe with the conductor details omitted. Trying to guess how that would work, I thought that the oil itself might be the conductor and that the large cross-sectional area of the oil is what kept the resistance low. Thanks for helping to explain how they actually are constructed and are designed to function.
Oil is always an insulator due to covalent bonding, or so I thought until I read in John Piña Craven's book that under extreme pressure - the bottom of the ocean - it can conduct electricity. He learned the hard way as he pioneered undersea engineering for the navy.
@@murdo_mck Sometimes the hard way is the only way to further humanity's understanding of science. The Curies are an example of learning the hard way. Sadly, their pioneering work into what is now called Radiology (the study of radiation) cost them their lives.
@@murdo_mck and just think - the lipids in your body work the same way. Under very high pressure, they are no longer insulators, which means neurons won’t work right. That’s one reason why creatures that live at the surface of the ocean can’t survive at great depth.
@@BlackSoap361 at what pressure does that happens? i think sea-elephants and sperm walls dive to 2000m or more
Underground cables, oil filled lines and SF6 switchgear is fantastic in space limited zones, but expensive and difficult to repair. Great, simplified explanation! These technologies are not going away anytime soon.
they are xlpe is replacing oil filled cables
I live on eastern long island and they just ran a 138kv (pretty sure thats what i read) line from riverhead NY to the shinnecock canal in hampton bays, probably about ten miles, and they ran it all underground alongside rt 27 sunrise highway. It took them the better part of a year, this gave me a whole new respect for what those guys did.
Needed more power as the Hamptons is tacking in so many illegals from the southern border. NOT
@@patheticprepper4496 bro what the hell is wrong with you. You randomly bringing up immigration . Get a grip. You are obsessed
This feels like a lesson in why you should design your infrastructure with an eye towards ease of inspection, maintenance, and repair.
This is the industry standard repair technique, for, what was by then well established technology. This particular cicuit suffered more mechanical problems than most due to elevation change along the route.
@@packratty They're implying that high pressure oil transmission lines were a bad idea in the first place. They're complicated to manufacture, hard to inspect, and difficult to service. Polyethylene isn't a new technology, it's what trash bags have been made out of for years. The whole system becomes much simpler when there isn't contaminant sensitive high pressure oil involved.
@@JMurph2015 HPFF lines predate polyethylene by a decade... and the line in the video was started a decade after mass commercial production of polyethylene began... HPFF was the best that could be achieved at the time.
@@benruss4130 polyethylene has been known about since 1898. It took until the 1950's before HDPE was being mass produced. This line was constructed in the 70's... Try again.
@@JMurph2015 nice try, it was discovered In 1939 on accident, commercial production did not begin until after ww2. Mass commercial production began in the 60s
HPFF lines were designed in 1931
I love that the ridiculously complex and finicky high-pressure, oil filled, high voltage lines, were replaced just by plastic covered cables.
overengineering at its finest
...Since 1989, R&D on high voltage transmission lines made them much more reliable...
There's chatter about Tunneling Systems being more cost efficient in the long run, but only in major cities. It might even be feasible to maintain a liquid Nitrogen System for Super Conductivity with no losses...
Too funny.
@2009G8Gxp Why would that be
Grady, the quality of your videos are always top notch. The way you put together your videos is always so good and the writing and editing of your videos is always great. But this video brought to light just how good your storytelling and narration is as well - you are a very good speaker! Thank you for sharing your passion for all things engineering and for putting in the time and effort to make these videos!
Hey there
I just want to let you know I’m studying electrical engineering and have recently started watching your videos and it has opened so many different Career paths for me I’m such a huge fan of what you do and how your videos explain everything thank you for everything you’re doing we need more people like you in this world
Hey wish you successes in your carrier! Never give up!
I spent the last 19 years of my career in emergency planning & response for an electric and gas company. People not in the industry seem to think that winds and trees are the only hazards to the electric T&D system and that undergrounding will solve all outage problems…
I'm surprised they actually went underground with a fluid filled system in earthquake country.
Sure, no system is perfect, probably you also agree that the rate of incidents for underground systems is pretty low compared to overhead lines ?
Hey how do we repair damage from a major geomagnetic storm? Like the carrington event, aurora as far south as colorado.
@@baratmalli6413 Are there enough high voltage underground lines in existence to make a comparison?
@@joe7272 graphine in the vax will cause the next carrington event to explode humans
"They also introduced a device known as the thumper, which introduces pulses of high voltage into the cable, though with an increased risk of sandworm incursion."
I can hear Joey from Friends saying "How YOU Dune?"
Shai Halud
The spice must flow
Applicability: Tremors > Dune,
Chronology: Dune ==> Tremors
Quality: Dune > Tremors
October 22nd can't come soon enough!!!!!
I love watching everything you produce. Your passion for engineering is contagious and your ability to explain in simply terms is a credit to your understanding…!
Such an excellent video! It's so great to see real enthusiasm for seemingly mundane things that are so often taken for granted. You've gain a subscriber!
Great video that clearly describes why oil-filled pipe-type cable is obsolete technology today. And it also partly explains why underground alternating current transmission is so many times more expensive than overhead transmission. But there is another factor that is not discussed.
When configured as cables, the conductors that make up a transmission line are physically far closer together than would be the case in an air-insulated overhead line. This change in geometry has several profound effects on the electrical parameters of the transmission line. The series inductance per unit of length decreases significantly - that has the effect of making the transmission line appear shorter which is often a very good thing. However, decreasing the phase-to-phase spacing also has the effect of dramatically increasing the distributed capacitance per unit of length of the line - which can be a very bad thing. Managing capacitance on transmission lines is a serious technical challenge; if there is too much capacitance, is may be necessary to invest in additional system components to manage that capacitance which further adds to the already very high cost of a cable-based transmission line.
The process of designing alternating current transmission is an exercise in managing competing factors. As a result, underground cables tend to be reserved for use in dense urban areas where distances are shorter, while overhead lines are preferred for longer distances in rural areas.
Direct current transmission presents a different set of competing factors.
That's why hvdc is becoming so popular...
Yes, and the capacitance and loss factor of the surrounds becomes a problem, where if a cable is only partly submerged in water it can fail, but is happy under water fully, as there is no step change in voltage gradient. Also why the outer sheath is important, a small nick in this can cause the cable outer shield to fill with water and corrode, and thus cause the insulation to fail at the edge of the corroded area.
Increased per unit capacitance can result in high voltage at receiving end than sending end. This effect is knows as Ferranti effect.
For underground, direct current makes things a lot easier since you don't need as many cables.
Another smart thing to do is to use a tunnel for more than one thing at the same time. For example, if you're digging to install a subway system, you might as well lay some power lines there, plenty of space and it probably goes to where you need power already.
I was unaware of DC HV systems until I drove by the Bonneville Power Administration Celilo Converter station outside of The Dalles, Oregon. BPA has some interesting videos about the converter station and other things. Grady could do a video on how they got thyristors to handle that much power.
This video takes back 30+ years when I was an apprentice electrician at a regional electricity supply authority. We spent over a week trying to find an intermittent fault in an underground protection system pilot cable running between two transmission substations. We were almost at the point of digging up the entire length of the 1.5km cable to find the fault when we decided to turn up the thumper voltage to "11" so we could "hear" the fault. We narrowed the fault location and start digging.
We discovered that a few years before a resident had driven a steel star stake fully into the ground above the cable. The point of the star stake damaged the protective sheath of the cable just enough so that it was no longer waterproof. Over the ensuing years, ground moisture seeped into the cable and degraded the paper insulation to the point where it was basically useless.
It was an interesting week of engineering detective work.
Oh man. What does that fine look like for the resident? I worked commercial landscaping and I can't imagine digging without locations.
I was an electrical engineer working with small electrical systems in native villages in Alaska. We were in a northern village with a bad underground cable. The locals reckoned it had gone bad at a splice, and they knew roughly where it was. Winter was on the way and the ground was beginning to freeze from the surface on down. To get through the frozen part we hiired a couple of guys to chop through the top couple inches with axes. Below this the ground was digable with shovels.
@@davidlee9870 I would have thought that these cables would be VERY deep just to make sure nothing got near them except for well digging.
@@richardiredale3128 deeper the hole the more expensive the job. From what I understand the high power cables are about 2.5-3m from top of cable to ground. But nothing is ever consistent
Paper is wood, is there no better insulator?
@13:15 And thank you Grady for yet another great production. I have been watching your presentations for years and you never fail to amaze me with all the nuances found withing civil engineering. You are a great TH-camr. Keep it up!
I'm a designer who is working on R&C protection for substations and yesterday, 6/14/23, I just learned about a new gizmo to pinpoint faults on a transmission line accurately. I'm new to this line of work though I've been here going on 5 years and never had any idea of the trouble with UG cable repair or have given any thought to finding the faults accurately. Figured that was all done already if someone would have asked me about it but I see that's not the case. Thanks Grady for all you do and especially for this episode. I've learned a ton from your vids and have gained much respect for those guys you see leaning on shovels not moving at that moment. I'm like you, perhaps I should say you're like me since I seem older lol. In any case, I really appreciate your videos.
Auckland NZ had a big power outage in the late 90s and Its a good story. The entire city center was unconnected to grid electricity for 5 weeks after several seperate underground high voltage lines overheated on a summer day with high loads. Cascading failure scenario.
The damage was permanent and the infrastructure was ruined. The lines company shut down the freight railway running into the area and strung up temporary poles between the rail sleepers (ties). Eventually replaced with a full new bored tunnel with room for expansion and human access for maintenance.
Quite drastic times though, they had to bring in diesel generators to power all the offices and businesses.
Thanks for the video!
They also built a temporary overhead line though a train tunnel down the rail way corridor to bring power back to the city.
@Robert Nelson it becomes easier when you can maintain them in a dedicated right of way and don't have to dig up streets doing traffic management etc. Plus gone are the days when engineers are the only voices that matter. I'm looking at you highway / road engineers in charge of urban environments.
Overhead lines are easier to break, easier to maintain. All tradeoffs really. It would certainly be easier to bomb a single HV tower in the middle of nowhere than an underground one.
They were also halfway through building their replacement in Auckland, if they'd started a couple years earlier then it would have been all good. Oops.
en.wikipedia.org/wiki/1998_Auckland_power_crisis
@Robert Nelson is it part of some kind of Supergrid project? Because those lines HAVE to be buried because they essentially have to be buried due to the fragility of currently developed superconducting materials
@Robert Nelson makes no sense in rural areas, but makes a lot of sense in city centers where the visual blight is noticed by everyone, all of the time.
When the thumper van shows up at an underground outage / short, site, it many times comes with one of the senior power lineman. When the equipment is in use, it’s amazing to watch that person feel that pulse with the feet, then ear to the ground and then paints an X, dig here boys ! Once again, when excavated at that mark, the fault is right on the spot 💝
A similar process of freezing the pipes can also be used on problematic oil wells. It's very dangerous and used infrequently, generally as a last resort.
This was a shockingly good video. I'm glad you covered it, I was too insulated from hearing it. Now I have a more grounded view of electrical infrastructure, and am amped up to learn more.
He knows his subject and it shows
Lightning quick reply.
Great video! As an electrical engineer, I really like understanding the unique challenges of old installations like this. BTW, in case you are looking for another infrastructure story, downtown Dallas has an interesting system of underground power distribution. Developed in the 1920s or 30s, the buildings down there have underground transformers (not that unusual), but the the secondaries (208V/3Ph) are all tied together between each transformer AND between neighbor's electrical services. Essentially, everyone is on the same low voltage bus instead of being interconnected up stream on the high voltage side of the transformers in a modern installation. Some of the buildings down there have 2, 3, 4 transformers dedicated for each building along with paralleling cables to tie the transformers together, but also to tie the neighbor's electrical service to your electrical service. They often include an extra transformers for what they call 'double contingency' shut downs, making your electrical service is incredibly redundant. there are some difficulties dealing with incoming fault currents which can be astronomically high because of the quantity and proximity of transformers to the switchgear.
Many of those transformer rooms people decide to shove racks of their computer equipment in. I worked with Unisys in the 200x's and had a few calls and was wondering why they had so many transformers down there. Makes me wonder how modern meter networks can work with such a system. Wouldn't you have to install a network bridge between each transformer or can a network signal survive the process with so many transformers?
Common enough still in urban areas, you have multiple transformers fed from the same 11kV 3 phase delta supply, all of them also connected on the secondary side by a separate heavy cable. This allows you to isolate a single transformer to repair or replace it, and not lose the connected load, though you have to be aware of the total loading on any one transformer, and they all have to be set up to provide the same exact ratio, so as to avoid large circulating currents.
Where I used to work there was a 1MVA transformer across the street, with a LC connection to the 200kVA transformer in the building, and another that led to the transformer 2 buildings down, which is a 150kVA transformer, but also a split in the 11kV loop, feeding a stub in a new building, as it was the closest substation when it was built. You can feed any of the loads from any of the transformers, though the 1MVA one you would have to isolate half the building it feeds, and also work at night after 10PM, as load will be low then. Feed fuses are 400A ones, and the outgoing cables to the local loads are 200A on all the transformers, just the bigger ones have more outgoing circuits.
There was a big notice on the fuse panel for the bottom 2 rows, which is where the back feed came in, that the lower contacts, normally considered to be the load side, can be live. You would just need to have 4 fuse carriers there, 3 with 400A fuses, and a single one with a jumper bar for the neutral, to feed the interconnect feeder if needed.
Had to do it for a few weeks when the fibre crew came a digging in the street, and found the joint in the 11kV cable with a pick axe. 10m of cable to replace the joint, and 2 scotchcasts, to join the tape armoured cable with the new HDPE cables.
I knew a person who was profesional electrican specialized in repairing industrial machines. And he called every machine older than 50 years flying dutchman since he never ever knew from where flying current will bite him.
i touched 100 volts. it hurt
@@Blox117 100 volts is kind of meaningless. It's like saying I touched a gallon of water. Did you stick your finger in it, or dump it over your head? Static shocks from shuffling your feet on carpet can be several thousand volts. Current, along with duration, need to be considered as well as voltage when it comes to calculating the effect/work/damage done by electricity.
Being an electrical engineer in the UK I find this fascinating, you explained so well and in such depth it was a joy to listen to.
The vast majority of urban power distribution in the UK is underground, I think this is correct since I don't see any overhead cables. How do we do it that doesn't mean constant failures?
@@JohnnyMotel99 Oil filled cables of this type weren't used that much. Some oil filled cables were used but tended to be of the hollow conductor type where oil was pumped through the actual conductor itself. Each individual conductor could then be insulated with paper impregnated with high viscosity oil, individually jacketed and armoured, and direct buried, rather than having multiple conductors within a pressurised pipe.
Oil cooling has fallen out of favour due to cost and risk of environmental contamination from the oil, especially as high voltage oils have historically contained PCBs which are a particular serious environmental contaminant. These days any new installation would be with polymer (cross-linked polyethylene) insulated cables, either directly buried, or in the case of some new installations in London, in deep bored tunnels.
There are some cases where polymer insulation is problematic, such as in HVDC as used in the various international interconnectors. The original England-France interconnector uses mass impregnated insulated cable as it is incompatible with polymer insulation. Whereas the new second England-France interconnector uses polymer cables routed through the channel tunnel, and the England-Norway interconnector uses undersea polymer cables. The difference here is that the original England-France interconnector uses old HVDC converters based with a "current source" design. A current source converter operates the cable at constant current, and the power transfer is determined by the magnitude and polarity of the voltage. So, in order to reverse flow in a current source HVDC, the DC polarity needs to be reversed.
The more modern HVDC systems use a "voltage source" design, which uses a constant voltage, and the magnitude and direction of current determine the power transfer. Voltage source converters are considerably more expensive and less efficient, but have much better controllability, have a number of grid stability benefits and can be more easily modularised and built at small scale. The constant DC voltage and polarity is necessary for reliable operation of polymer cables. Inuslators are never perfect, so there is a tiny leakage current through the insulation. Additionally, the polymer molecules act like tiny capacitors. So, over time, the polymer becomes electrically charged internally.
The problem with CS HVDC is polarity reversal. If the conductor is at +500 kV, the interior of the insulation will slowly charge up to a high positive potential (maybe +400 kV a few mm from the conductor), and this charge would be trapped by the high resistance. If the cable potential was reversed suddenly to -500 kV, the trapped potential in the insulation would result in a potential difference of 900 kV across a few mm of insulation, which would result in arcing and destruction of the insulation. In a polymer cable, this is a catastrophic failure. However, in a mass impregnated cable, this will blow a hole in the insulation, but if the cable is allowed to rest for a bit, the oil will ooze out of the neighbouring paper to fill the hole, and the cable will self-heal. Avoiding this type of insulation failure means that power flow reversals over a CS HVDC link must be done slowly over several hours to allow the trapped charge to leak out
Electrical engineer here from the US, what is the salary for an EE in the UK?
@@djaztec97 it ranges massively, depending on the type of work you are doing and the contract you have.
The average wage for an employed electrician, is about £32k, if you are an approved electrician about £36k.
If you are a subcontractor working on a temporary basic for a larger firm, and you are on a day rate, that can range from £200-£300+ a day.
I have friends that are standard electricians and they run small electrical company’s, and make earn around £50k a year.
I am an employed electrical technician and I do mainly large industrial project and my base wage is £45k plus bonces, and I have a company van and other benefits.
However if you are a genuine EE with a full degree in power engineering, i know it is possible to earn £100k+
I believe that the electricians in the US earn a lot more than we do in the UK.
Man! I came across those old mailing list postings a million years ago and was FASCINATED. Nuts to find you talking about it.
Honestly this helps make the PG&E fire hazard wire plight more understandable. I hadn't really considered how much additional engineering has to go into putting cables like these underground, as opposed to the more readily available and simplistic approach of stringing them out in the open. Thanks for the interesting perspective!
PG&Es issues were caused by foliage (trees) touching overhead lines
@@getbetterben4312 same with SDG&E. They’re still paying off lawsuits from the late 2000s regarding wildfires started by their poor management, which is in turn being payed through double digit increases for ratepayers for many years to come
@@getbetterben4312 And, from what I understand, not replacing the wood poles.
Stories like this are what I grew up on. Being poor, I had a very, very slow (seriously 1200bps...) modem on my aged but reliable computer. The early internet to me was all text - newsgroups, gopher, telnet... I loved hearing about things like this; big elaborate repairs that nobody really knows are going on.
I remember the day I finally decided to drop $50 on an internal 2400 modem. Wife was ticked that it went in the BBS machine rather than our personal machine, but the users were happy...
The old days of the internet.
What are you bragging about? In those days our family was still on waiting list for landline. In big apartment complex in town.
@@rybaluc That was about two years after I finally got my own private line, and didn't have to share it with 3 of my neighbors.
@@kevincrosby1760 Back then modems were not even allowed in my country. You could get to jail for using them. After revolution in 1989 they just approved faxes first as i remember. But most people were in 10-20 years waiting lists for landlines anyway at that time.
Fascinating. I first learned engineering from my father, who was the head of the "System Protection and Electric Test Dept." of the utility serving most of Maryland. The used a continuous flow system in their underground high voltage trunks, with the oil flowing in opposite directions in parallel pipes. To my knowledge, they never experienced the described sort of cable failure. However, they did experience a spectacular failure once when the terminating equipment at the load end of the trunk overheated and exploded within an underground equipment vault, resulting in a flaming jet of high-pressure oil blocking access to the pump controls, thus requiring some innovative engineering on-the-fly to depressurize the system.
That was probably a different adrenaline rush than they expected.
Pressurized oil is scary as f*ck.
Near where I live there is a Krupp steel mill. 15 years ago or so there was this small fire, something insignificant, that you can put out in half a second with just a spray from a fire extinguisher.
But it was right next the hoses of extremely pressurized oil of a giant press.
They sent a crew to put out the fire and they did it. But then the hoses, damaged by the fire (and likely already way too old), ruptured.
Most of them just disappeared instantly, like the shadows of people on concrete walls in Hiroshima. Other workers just a little bit further away weren't so lucky.
Scary, scary stuff.
@@qdaniele97 Hydraulic systems are much safer because they instantly depressurize unless there is an accumulator in the system. In a normally designed press, all they would have had to do is power down the press and it would have been fine. Even if the lines were still pressurized and one ruptured, as long as the pump was stopped it would instantly lose pressure.
Thanks for the lesson to not take power for granted. Incredible how much complex planning is involved just so we can have easy lives!
Great storytelling, you bring it down to the appropriate level and just keep on moving! Great job! I’m a retired engineer/operator at nuclear plants and your explanation is easy to follow. Thanks for spreading the good word!
Was kind of expecting an ElectroBoom-style model when talking about the underground high-voltage arcing challenges, but I guess that's a collab for a future video!
please no
My line of work requires me to find underground faults in wires. I wish my coustomers would watch this so they can begin to understand what I have to do. I can't imagine having to find faults in this type of system, just regular wires have so many variables and not to mention interference! Awesome video!
I have a break in a regular cable in an apartment somewhere in a concrete wall. The electrician said that he would have to open the wall and lay a whole new cable line from the box, make repairs to the premises, and so on. Extremely not cheap. I have to use a regular extension cord instead))
I can only imagine how difficult and expensive it is to work with industrial cables. Feel for you
@@Tony-. Yeah, I think that if I ever remodel or sth I'll put various cables behind removable panels. Cement it in and forget sounds like a good idea on paper... in early 1900s :D
@@justcows7772 I agree, I do not expect them to, BUT when they observe and instruct me to do things the know nothing about, I feel maybe they should at least have some common knowledge on the subject they are speaking about. I always smile when I ask if they know about electricity, or fault finding, and the almost always start out by saying " I owned _______ up north" or " up north_________" . Just had a customer on Wednesday questioning me every 5 minutes and telling me their system was not in the area I had detected a fault, only to dig it up and expose the fault to them, and then repair their down system.
@@GerinoMorn usually cables are run inside a conduit that can be accessed from the roofspace, fairly simple to pull the old one out and repair or replace it
The guy at the beginning that noticed odd construction in his neighborhood though should’ve had a scanner radio. Then he could’ve just listened in and found out quickly.
OUTSTANDING VIDEO! One of the BEST descriptions of underground HV lines. Thank You for the work!
One of the best channel on youtube! Thanks for doing this! :D
Putting the "real-life stories" into the explanation of how large scale infrastructures are built or managed really adds a nice flavour. More over, it helps explain why some works takes really long time! (Even though I challenge you to explain the extremely long time in contruction works here in Italy! XD)
ps: maybe you could find interesting (and I really would be curious to hear and understand) how the construction of the new metro line in Rome was, is, and will be doing :P
Excellent story, it reminds me of a visit to an analogue telephone exchange when I was a primary school child. The fascinating bit was in the basement, below Street level. I had noticed a big chamber with the exchange cables going into it. I was aware it was a pressure vessel due to the number of bolts on a flange cover. I enquired to the guide about it and he said that was the main feed from the telephone exchange to the underground network across the city, it was a pressurised bulkhead that connected to sealed pipes underground that carried the cables. He showed me the compressor room full of huge tanks and compressors and the battery room.
He explained that the entire telephone network cable system (main trunks) that were underground were in pressurised pipes to keep water out and that the network had the battery room so that in an emergency or power cut the telephone network can keep operating for several weeks, even during severe floods due to the sealed and pressurised trunk system.
I was probably about 10 then and I have always loved the ingenuity of the engineering.
Sad these days with everything power hungry and digital. Nothing will work in a severe flood, large disruptive emergency or power cut, at least not for general use.
I recently had a small pipe burst in my home and the plumber I called also froze the pipe from both sides of the fault so he could easily and quickly install a new piece of pipe without disturbing the water supply to the building. Cool to see it used in such a large repair job too.
You should never freeze water pipes, water expands when turned to ice and will cause tremendous stress to pipes. I wouldn't be surprised if, in the future, the pipe bursts where he froze them. That's what valves are for, put them in strategic locations and you don't have to resort to dangerous improvised methods.
@@Rayden440 you should go look it up it’s quite common.
Especially in hospitals where shutting off water could actually be deadly
@@Rayden440 Take a look at some plumbing tool suppliers and methods and you will find it's reasonable and safe, properly done! In some instances, it's the only practical way to make a repair! ¯\_(ツ)_/¯
They don’t freeze the entire pipe so the plug expands into the unfrozen section. Steel is stronger than ice/water as long as its not sealed in…
@@Rayden440 that actually isnt correct tho, since you freeze the pipe in a non enclosed state its even safe, the ice slugs can expand into the pipe itself and dont need to pressure the pipe around its circumference
Its even common practice if you cannot shut off a line because its paralel to other clients also receiving water which cannot be interrupted
There is another procedure used for large gas pipelines if they cannot be shut down where they essentially live tap the line twice and then seal in between with 2 more taps where they insert valves but that procedure is NUTS
Can’t get enough of your videos. You explain things simply and elegantly. Even a complete non engineering person like myself completely gets the gist of all of it. Thank you!
I spent a year as a Subcontractor to a major Cable manufacturer wiring the oil pumping stations used on the East Coast underground HV distribution system. I never really knew how the system worked just how to wire the power and controls for the skid-mounted pumping equipment. It was one of my last projects before retirement. Thanks for the story.
I appreciate your proper use of significant figures in conversions. As an engineer it's a pet peeve of mine when videos will take a rough quantity in one unit and then convert it with far too much precision. Your use of "approximately 14" bar approximating to "200 psi" is a great example. Many videos would quote that as 203 or, worse, 203.1 psi when it's just a rough value in the first place! Thanks for adhering to good engineering principles! Subtle things like this ARE noticed!
Significant figures is not the proper way to propagate error. It is a set of "rules of thumb" and can be show to be self-contradictory. I have no problem with dropping figures off of estimates, but it kills me when professors act like it is based in rigorous mathematics, like 'you didn't fudge this number in exactly the right way.'
@@MushookieMan i don't know that sig figs are really a thing engineers use. I certainly don't.
In general it's about understanding the scale your working at and how good your tools are.when I see someone report the temperature of an air conditioned volume to 4 decimal places it tells me that they fundamentally misunderstand the problem they're solving and the tools they use. Humans can't tell to that level and no air conditioning system will be able to control to that level. For a newish engineer it's a training issue, for someone who has been around for a while it's a warning about that person's work.
@@Kandralla As an engineering student I typically prefer to use full precision for intermediate calculations, then round the final result based on the application and original data. While I understand sig figs and why they are used, I always thought the specific rules felt arbitrary. Rounding with each step also felt like I was accumulating successive roundoff errors more than keeping the scope of the calculation in check. In fact, I've always preferred to err slightly on the side of "too much precision." In the real world, who cares if I report a value down to 4 or 5 decimal places instead of 3? That extra precision can easily be discarded later; it's a lot harder to get back once lost.
@@andrewsprojectsinnovations6352 the too much prezision can become pretty costly realy quick like i want to buy 10,0m of steel that can be from 9,95 to 10,04 in theory with rounding and is easily doable with an hand saw, now 10,000m gets in the range for maybe needing a temprature controlled messering room making the price probably go up by a few times also most times when you give like a mm number with more than 1 or 2 dezimals the question also becomes how do you want to messure it and that also can become realy costly
@@andrewsprojectsinnovations6352 the reality is that for most situations the limiting factor is going to be what you can sense, and what you can actualy control to. For a lot of jobs it's more important that you're consistent with whatever you do then it be "the right way". Where it really really matters you're going to have standard practices that are industry, company or even job specific (and if you don't... And it really does matter, write your own and put it somewhere people can find it). It really comes down to you understanding what the numbers are used for, to what level of precision it matters, and what precision the numbers you start with are. But if you're reporting to five decimal places and it's unwarranted you're sending the message that you don't understand the scope of the problem you're trying to solve (and 5 decimal places... That's up there no matter what you thing about preserving precision... It's false precision in most cases) .
For me, I minimize the number of times I have to round something just out of habit, but for what I'm doing it doesnt matter all that much most of the time.
That oil insulation system looks crazy expensive to maintain. I’m amazed that someone decided to actually implement it.
Oil and paper insulation is still commonly used for step-down transformers all over the US, so I'm not surprised it was seen as the de facto solution back when the line was installed. Definitely a very expensive endeavor though
Still the only thing used in large transformers, as the paper does allow gas to permeate, and also will not trap bubbles. All power line transformers, from the baby 1kVA pole pig, to the 500MVA monsters used in distribution, use mineral oil as insulation and coolant. Even the instrumentation transformers, used to tap off line voltage and current, so as to monitor the line, use an oil fill and paper insulation, especially at higher voltages, where you cannot guarantee the epoxy fill is going to be totally void free.
@@SeanBZA In that application the cooling is at least as important as the isolation.
Overhead ain’t cheap either, and there is lots more of it, just think about the distances.
@@timan206 Yes, but overhead is cheaper because you do not have to dig a long deep trench, just put in foundations every 50/100/200m, build a tower up out of standard steel sections, and then suspend a row of insulators, and a 1km long pull cable, then use that to pull 1km of cable at a time onto the insulators. A lot faster, and you save on the plastic as well, replacing it with a much cheaper air dielectric, with ceramic/glass or polymer insulators on the poles.
Thanks Grady, this answered several questions I have pondered over the years. Great job as always!
That was an incredible video! I never know how much work was put into those power lines and also how they basically futureproofed aforementioned lines
Grady, I've discovered your channel about a month ago. I've basically binged all your videos. I am not necessarily an engineer, but have always been a bit of a nerd and love to learn about technical things.
Thanks to you, I now count isolators on overhead power lines on my commute home and told the group I was golfing with that the large powerlines were sagging, because they were probably pretty warm.
Thanks for making me the "weirdo" in my group and keep up the great work!!
after binging all those videos I hereby grant you the title of PE, practical engineer 😜
I've been enjoying these vids for about a year, and yes, they're fantastic. I think TH-cam recommended it to me when I'd run out of Real Engineering vids to watch. If you haven't found those yet, you might be in for another binge. 🙂 Enjoy.
Tower line fault: "We need a helicopter"
Underground line fault: "We need to perform brain surgery on the city"
@@simeonpetkov768 no I meant tower
This is why when people call for all powerlines to be buried to prevent wind storm outages, I disagree with them. Sure wind storms won't cause you to loose power but if an underground line fails it is orders of magnitude more expensive to fix and takes orders of magnitude longer to fix. There are no perfect solutions, only tradeoffs.
@@crissd8283 You don't have to bury all power lines to reduce wind storm outages. Residential power lines that are above ground are much easier to maintain underground than the high-voltage ones in this video and they're going to be the bulk of the repairs after a major wind storm. You're not going to prevent outages from wind storms severe enough to affect the high-voltage towers, but those towers are less numerous and thus quicker to repair. When there are tradeoffs, the right solution is usually in the middle.
The time difference between overhead and underground is huge. Time is critical when you have a HV line out. Problem is if you lose other lines while you are still working on the original problem you are in big trouble because of cascading outages.
@@raiden24 I agree, the right solution is in the middle.
We need to revive the concept of "engineer for repair" and teach it as a basic part of every design course and maybe even include it in the engineering code of ethics.
I am a maintenance supervisor and maintain a system like this , I have also visited LADWP to see their system and the requirements to maintain and upgrade are understated. Our system is under vacuum and has a parallel return line to avoid the reversal and allow a continuous flow. In addition to increase capacity we have chilling systems for cooling and the entire system is computerized and has become extremely complex for all aspects of O&M. This is a great introduction to this system and thank you.
A company here in my city has been part of PG&E's study of how to keep their electrical lines from starting fires in California. The idea of running these lines underground is a good one, but even with a "mole" drilling beneath the soil, it seems like a logistical nightmare. Those lines have to go up and down some serious foothills, through every type of rock from weak shale to impenetrable granite. Interesting stuff all!
Sounds like a job for the boring company , a small sized tunnel made with small boring machine
@@Mr2winners yep, all it takes is $$. They make nice rock bore rigs for just that.
Not only do you have the various types of soil and rock to deal with, we also have earthquake faults as well. PG&E's also accounting for this when running these underground lines?
This series is really starting to give me a lot of unneeded anxiety about the fragility of all the infrastructures we humans so desperately depend on….
US is pretty far behind in proofing though. The for profit model is very vulnerable, since most systems are made cutting costs and hence corners. Countries with public single payer systems tend to have a lot more low cost safety measures and redundancy, to protect against eventual failure.
You definently don't want to read anything about The Carrington Event, then.
@@lookingforsomething Then ' low cost safety measures and redundancy' should be built into the contract.
@@Torgonius Or the ‘Year Without a Summer’.
@@djg585 Sadly this doesnt come cheap. Speaking as someone in public sector procurement ignoring the additional upfront costs of additional features(which i agree redundancy and quality are worth the cost hence the ignoring), we have a bunch of easy ways things can go wrong because sadly humans are involved
1) You need to make sure that theae additionals are actually being done
1a) This means inspections and having either a third party or someone with the technical expertise to do these.
1b) Even with these inspectors do you have them on site 24/7, do you do spot checks, do you check at specific parts. All have varying extra costs.
1c) who inspects the inspector bit silly I know but people can make a mistake miss things, be occupied, be ill or called away for an emergency.
2) You also need to validate all the equipment is above board and actually of the stated quality. Supply chain management is a big expense costing a large amount of manpower initially and then continual manpower. Multiply this if international supply chains
3) Contract Managers(people) are more often than not one of two types, those that focus on the contract wording know it inside and out or those that focus on the actual day to day practicalities. Both have ups and downs. You need either multiple people (more costs) or a rare person able to do both (rare and likely more costs).
3a) example as to why the first type can be problematic, not understanding the day to day real world applications can lead to inefficiencies and a very heavy handed approach
3b) for the second type focusing to much on being pragmatic and practical can by even just repeated actions (not even written) lead to a change in the contract in the eyes of a court if ever brought in front of them and then all the unintended knock on effects.
Sadly contracting isnt as simple as it might seem and go's far beyond just say this is what they must do and let the lawyer write it up(and lets not even get into lawyers even in the same team having different opinions on the interpretation of the same clause)
Just watched this for the first time today, 11 months later, but I'm always fascinated by your outstanding videos, Grady. We have a very conventional short distance underground line where I work and it can present maintenance problems too. It's "only" 13.8KV and goes through a couple of underground vaults. Now that it's approaching 25 years old, the question is arising about what it will need for replacement or upgrading. Pumping insulating oil through the conductor pipes is one possibility. Also, we have a glycol loop in the plant which recovers heat energy from our turbine-generator exhaust stack. The loop has something like 2500 gallons of ethylene glycol in it- not simple to drain. We've successfully used LN2 for freezing off and servicing this system, though it did take several tries before they got the calculations right and actually sealed off the lines. Thank you so much for Practical Engineering!
Thanks! You really do have supreme synthesis skills on extremely complicated topics.
Repaired a couple underground primary’s to some houses. Impressive how even underground they are still susceptible to damage from nature.
Interesting stuff , I didn't know this and I was a pole and line inspector for fire mitigation and never heard of these underground HV problems🤗⚡⚡🔥🚑💨
considering plate tectonics are known, I think the probability for something underground beeing damaged should be higher than overground? 🤔
@@BlackDragonWitheHawk plate tectonics can damage at such small scale?
@@shadmansudipto7287 Well, it is plate tectonics that cause the smaller fault lines. So, a couple degrees of separation? :)
Saw a cable section where the 66kV cable decided to fail, and it made a new hole in the road. Despite it being buried some 5m down in the ground, it blew a hole the width of the road early one morning. Made the cast steel joint box go from round to flat, split at the weakest part of the casting, not the bolted seams.
I had to come to watch this as soon as I learned from Tom that you'd made it! It's one of the all-time great engineering stories, and it has always pleased me that I'm mentioned in the original, even peripherally! I love what you've done with it to adapt it to the medium. Focusing on the basics up to thermomechanical bending to give context was a good choice.
Thanks, Grady!
I remember reading about this story when In my teens. It was certainly part of my inspiration to become an engineer. I grew up in Sweden, so this story had some reach, even in the early 90s.
I really appreciate not having some midroll ad in this video, just a clean cut to outro
this is one of my favourite channels !!! you have such a chill energy thanks for all the vids
When he started talking about fluid hammer, I expected him to say that there was a major pump failure that caused a pipe rupture. I'm glad there wasn't, because this version was much more interesting.
I'm guessing a pipe rupture would be a Very Bad Thing. First you'd have pressurized oil spraying all over, then the lines would arc, ignite the oil, etc.
Jeez, I like to hear engineers discuss things. They are, as a rule, very rational and understand how solutions are invariably tradeoffs between competing goals. Plus, they recognize that bullshitting is a waste of time and results in incorrect conclusions being drawn. Thanks for the clip!
Sadly, not always do they admit that their solutions are bullshit :))
@@Numerlon It doesn't matter if they admit it or not, because when reality steps in and demonstrates a solution doesn't work, it's pretty clear to everyone it was bullshit, a bad design, and they effed up. Like Mulholland: when his dam broke and killed a bunch of people - he was devastated and his life was destroyed.
@@jonahansen that proves exactly why ot does matter. He couldn't have some humility and people died because of it.
@@jonahansen trade-offs between competing goals? No no, the bean counters *always* win and post production service personnel get fucked for decades after.
while rational, engineers are good to let to be in leading position in huge infrastructure projects, but not always in designing smaller items for consumers.
nokia died because they let engineers design their phones, with no input from model designers or operating system designers.
the newest tesla car, the plaid, has perhaps the automotive history´s worst steering wheel and how it feels and looks from the inside. it is marvelous technical wonder, years ahead of everyone else in electrical engineering of cars, yet only enthusiast will want to buy it. people wont get interested on tesla until it brings fully self driving cars. and don't make people pay 150k for it. china already has full autonomous cars with autox taxi program.
You are one of my top 5 TH-camrs -- if not one of *the* top 5 -- and I particularly love this package, as it gives me something with which hit Tampa Electric over the head as they continue to make noises about undergrounding distribution to avoid storm damage.
"How do you repair this?" is a really important question that engineers need to plan for. (Especially automotive, but that's a different channel...)
How about redundant lines. Disconnect the dud . Turn on the new guy.
I both install AND maintain the systems my job produces. Which means I DO NOT install my cables like you see in those "Cable Porn" photos. Those God forsaken hellholes are a nightmare to trace, troubleshoot, and repair. I leave slack in cables and make it easy to poke around in later when something goes wrong. Yes it often looks like crap, read the labels and you'll see the system in place that makes it easy to navigate and fix.
@@johnalden948 This is commonly done nowadays in individual buildings with CAT-5/6 networking cable. The labor is the expensive part now, so running a second cable as you are running the first does not cost that much extra.
For power lines that would be extremely cost prohibitive.
that is something engineers are horrible at, they never consider repairs.
Apple engineers: how about no
Grady, I have a super interesting story about how they used liquid nitrogen and cooling units to freeze a tunnel wall for a tunnel that they were boring underneath a canal in the Netherlands, especially interesting because the ground above and around was sand. Let me know if you want to know more. I do not know everything about this story, but maybe I can give you some pointers where to find out more about this :)
That’s a fairly common approach for tunneling through wet, unstable soil. They don’t always use LN2, but the concept is the same wether they are using it or brine.
The same method was used in the 70s in Romania to build an entire metro station in a rather swampy area in Bucharest.
Similar thing was used in Paris to bore the metro tunnels at the beginning of the 20th century, except they used ultra-cool brine to freeze the Seine river.
@@titusicleanu7431 And in Leningrad, also in 1970s: the tunnels failed 20 years later and it took 9 more years to build new ones en.wikipedia.org/wiki/Lesnaya_(Saint_Petersburg_Metro)#Geological_conditions,_washouts,_building_and_repairs
Really interesting stuff, I was told it was quite rare these techniques were used, but reading all the comments, it turns out it's not that rare after all!
Here's a video on the frozen boring in the place I was talking about:
th-cam.com/video/5vNX3fwE-bg/w-d-xo.html
Mind you, this was done underneath a monumental (one of the two oldest) train station building!
After doing some more reading on the topic, it actually wasn't boring, but it was only a 4-meter long section that was done by hand. They had to freeze a 2 meter thick area around the hole to make the hole stable so they could dig out the final piece of the tunnel. They had approached the wall from the backside with a boring instrument.
It was quite a feat, this was part of a project called the 'Noord-Zuidlijn' and involved boring a tunnel underneath the capital city of the Netherlands; Amsterdam.
Here's more info on the techniques used in Dutch:
noordzuidlijn.wijnemenjemee.nl/tijdlijn/bouwtechnieken-noordzuidlijn-in-de-beginjaren/index.html
Another superb and fascinating video. Love this channel ❤
Also much appreciate the metric units on top of Imperial. Just please do it across the board, so that you add "centimeters" to "inches" and "kilopascals" to "psi". Thanks again for your amazing channel. I never miss a video! 😃👍
In 2014 I worked on “The Scattergood Unit 3 Repowering Project" to improve plant efficiency and responsiveness (as well as to finally stop seawater cooling of the original plant) and people were still talking about that cable. Thanks for giving this story new life!
What a fascinating story. Partially makes me wish I would have stayed with general engineering in college instead of switching to computer information systems. However, I must say that stories like these give me a profound respect for engineering of all types and the professionals behind those fields.
Okay, so now I understand why "just put them underground" isn't such an easy solution to the problem of failures in overhead transmission lines causing wildfires.
just make wireless power 🙃
@@BlackDragonWitheHawk B)
@@BlackDragonWitheHawk just have a rotating shaft transmitting the power
It is an easy solution, it's standard in Europe and works fine. Typical American incompetence
Yes, can see why giant chainsaw dangling from a helicopter is actually more practical now.
Grady?? How appropriate! Another great offering, PE. I learn so much from these information packed, well-presented posts.
This is just too cool. It's also badass that you went out and found the original poster and talked with them. I write software and debug electronic circuits for a living. I have always had a fascination with high voltage generation and distribution. It's fascinating as the rules just go wild with high voltages. Everything I work with 5-12 volts, where there is relatively little weirdness. Granted complex digital logic does have its own quirks. I love your videos....just straight engineering and physics with no fluff or filler.
The Auckland power crisis of 1998 would make a good followup to this, another case of underground power lines failing
70k people’s offices mostly useless and 6k residents without power. 5 weeks to be reconnected to the grid. Although temporary power was restored after a couple days.
Quite the disaster.
Link for those interested.
en.m.wikipedia.org/wiki/1998_Auckland_power_crisis
It was the week I moved into university accommodation in the cbd, quite a disruption
"The two cables [...] were 40-year-old gas-insulated cables that were 𝗽𝗮𝘀𝘁 𝘁𝗵𝗲𝗶𝗿 𝗿𝗲𝗽𝗹𝗮𝗰𝗲𝗺𝗲𝗻𝘁 𝗱𝗮𝘁𝗲."
Well, there's your problem.
It merely illustrates that 𝘱𝘳𝘰𝘱𝘦𝘳 regulations are an essential part of civilization. For example, a mandatory rebate for outages over 4 hours, is no rocket science, yet a powerful disincentive against utilities sweating their assets.
One of the annoying things as a utility engineer after a storm incident is having to hear all the questions of "why don't they just bury the power lines underground so they can't get blown over"?
Thank you for highlighting some of the issues with underground power cables, they aren't always the best option.
Long term the cheapest and enviromentaly best option would be to build utility tunnels under every streat which make a combined easy access for running water, sewage and electricity and whatnot in accessable pipes through them.
Always.
But humans don't tend to think longtherm and for building the costs for this would be massively higher...
use goddamn utility tunnels like europe has been doing for decades and most of the problems disapear.
I was "one of them" that used to say this all the time after hurricanes topple power lines in affected areas. I was always "told" or "heard" that one of the main reasons power lines aren't buried is due to power-loss from source to user, is higher for buried power lines. I'm not even sure that's true, but this video highlights the drawbacks to buying them, that's for sure.
I so enjoy your channel. You do such an excellent job explaining in layman's terms how our society gets things done. Thank-you so much for taking the time to put together such an interesting and informative channel.
Thank you Grady for this amazing video. I think it’s awesome that the technology we have at our disposal can be uniquely used at varying degrees of necessity.
Could you do a video on more modern underground cabling? I'm curious if the cities in Iowa that do this have similar limitations, or if engineering advancements have found other solutions to this problem. It would be interesting to see how devastating an earthquake could be, since heat is SO much more important in Iowa than in LA.
I had just started at DWP when this happened, but was working on relocating the underground 138kv transmission line for the Century freeway.
Miss that old lead covered, paper insulated, oil cable...good for 100 years if maintained propery.
Now we get 20 year synthetic covered cable..🤔
@@dougw5950 There's a reason the newer cables use different materials. It's because the newer materials are better.
Absolutely fascinating, and such a great job explaining the situation and process to repair. Thank you .
I JUMP when I see a New Video from you, Grady. The time/effort is terrific!
I find it interesting that the old power line is still operational though only as a backup standby line.
I grew up in Silicon Valley. When I was little, it was filled with fruit orchards and yes, power lines. Sometime in the 70's, the whole thing changed and they started the big project of putting all the lines underground. They did the phone lines too, with that new-fangled "fiber-optic cable". It took a long time, but eventually, the power lines were all gone. It was great!
But I never thot about what would happen if something went wrong on the line. I don't remember seeing any crews working on it, but then it may have happened after my bedtime - as most of those photos show it happening at night. Fascinating!!
During Hurricane Ida, there was the usual chatter about _"why don't these people move to somewhere above sea level???"_ talk, but also, _"why don't they bury the power lines???"._ Now that I see the trouble involved, I doubt that city has enuf $$$$$$$$$$$$ for that kind of infrastructure. Sunnyvale, yes. Los Angeles, yes. But not New Orleans.
Even in northern Louisiana the water table is quite high. Most houses don’t even have basements levels of high. I can’t imagine wanting to put high voltage lines under ground down there.
Watched every second of this episode, and quite illuminating for me (Only familiar with insulated cables), how engineers could think such incredible laying strategy and repair methods at that time. WOW!
This is one of the most interesting videos I have ever watched. The genius of civil engineering is that residents never have to think about it until something goes wrong.
I live in a development with just over 250 single family detached homes, where the electric power is delivered underground - but at voltages considerably lower than a transmission line of course. We get occasional power outages, and they have always been due to faults outside of the development (the power company outage reporting system will give the quantity of homes affected by an outage, so big numbers point to the problem being outside the development) - except for one winter day.
On that winter day, when I was getting the update for number of homes affected, it was only ten homes. Which means the problem was not just within the development, it was on my street.
There was a light snow in the ground when the power repair crews showed up. It didn’t take them all that long to find where to dig … the snow is wasn’t sticking where the fault was, because of the heat that the fault produced. A lawn two doors away was dug up where the snow wasn’t visible, and that was as where the repair was made. Apparently, when the line was originally installed, some sharp edged rocks were beneath or on top of the cable, and that was enough to pierce the insulation.
BTW - the repair crews did have some fault finding equipment that they could have used, but Mother Nature and physics allowed them to avoid the need for that equipment.
Whether the fault in the transmission lines of this video could have been detected by heat … hard to say since the oil had a heat sink effect. Maybe would have been worth a try.
I don't think it'd be possible to detect it from the surface by heat. 230kV lines are 9 feet below the ground, at least where it's coming into the station. I'll have to ask my old boss if I ever see him again how far below ground the run is
@@brimmed The typical distribution voltages from my residential supplier is 12.5 kV and 25 kV. My last home had a municipal electric company, and they replaced their distribution wiring by pulling a plastic raceway from a directional boring machine. I doubt it was 9 feet deep, likely only 2 or 3 feet deep.
@@johnhaller5851 LMAO, he’s not talking about the baby lines that feed your house or neighborhood...There are standards and 2ft is hilarious, maybe they just leave it on top of the ground...
i love things like this because it shows the impact someone's slight interest in a subject could have such big changes for someone else. I enjoy learning about things and your channel really is so cool. It's like a How It's Made, but more How It Works...
How It's Made is such an interesting show
wow.. this is crazy fascinating. Thank you for explaining it (and educating) as well as you do!
this is pretty much a history documentary on engineering. great writing!