EEK! #7 - High Voltage DC is back!
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- Опубликовано: 1 июл 2024
- We all know that AC won the war vs DC back in the day. But did you know high-voltage DC is still around? What's more, it's actually become quite useful! Some countries have recently installed million-volt DC power lines that span thousands of kilometers. While HVDC has various benefits over HVAC, naturally there are also a few drawbacks. Join me for another exciting episode of EEK!
Previous EEK! videos that explain current, voltage, AC, DC, 3-phase AC power, RMS, Power Factor, and other exciting topics:
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As Robby pointed out, the Brazil HVDC link is 6300 MW or 6.3 GW, not 6.3 MW. Thanks for the correction!
In my company (isp) I'm using DC 330V (european 230v ac rectified) the sockets are marked red, and it is only for sensitive electronic, computers, core routers, switches, everything that uses switching power supply. This scheme allows me to jump over UPS, and use batteries in parallel. No relays, no power ups, no reactive power, no power line distortions, no complications. Works like charm for 17 years.
12 gigawatts!! thats more than Doc. Brown needed to get back to the future!
Amen... and to say nothing of the flux capacitor
I work as a field installation specialist for large HVDC projects, i did the 1100 project in China and have done many other 800 project in India.
1) You can't run a 1500 mile AC transmission line as the inductive and capacitive losses cause the power to reflect back rather than move forward
2) You can't just connect two grids together and call it a day, they must also be the same *frequency* and *in phase.* There are many regions of the world where adjacent grids that need to be interconnected aren't even the same frequency at all (Japan), much less in phase for that matter (Mainland Europe) - HVDC solves those hang-ups
Thanks Scottie !
Excellent explanation. Concise yet thorough. Thanks a lot bro!
Cool mate - Love your work! 👍
Thank you for such clear and compreensive explanation!!!
Very informative and well presented. Thank you.
Thank you for that great explanation! Would love to see a hvdc circuit breaker demo.. Your a good teacher! Thanks again.
I hope there's DC transmission to house. because most appliances rectify AC to DC first, even motors use its own inverter for variable speed and higher efficiency. and using DC system, it's easier to use battery backup and solar power system eliminating need complicated and expensive inverters. just some simple voltage regulator and it will be much more efficient. the voltage may around 300V DC to home.
Seems like a main long distance transmission grid in HVDC, regional transmission in HVAC, and end users with low voltage AC would be an optimal path forward. Leverage the strengths of HVDC and minimize the impact of drawbacks through keeping the required infrastructure and cost minimal.
The big reasons for 2 wires on DC, is:
1 Detect ground faults. An insulator may fail and this protects the equipment by detecting current on the ground. Works just like a ground fault breaker. Uneven current trips the safety.
2 Prevent ground current. Natural ground current from a CME can interfere with proper operation of the line. Lightning strikes can damage equipment.
3 DC ground current will remove the anode side electrode through electrolysis. Eating off the ground conductor will surly disrupt the current.
4 Lower voltage inverters. A 1 Mega-volt line is 1 Mega-volt between conductors. Each inverter station uses 2 converters, each running 500 Killovolts. One is positive and the other is negative.
The converter stations are much more expensive than transformers and power factor correction capacitors and reactors, so they are used exclusively for long haul power transport where inductive losses are more of a problem. The DC Intertie in the USA is between the Columbia River between Oregon and Washington and goes to a converter station about 60 miles North of Los Angeles. Originally the line was 500KV, but recently upgraded to 750 KV. This link primarily uses hydro power from The Dalles Dam, and uses the spring snow runoff to power the air conditioners in Southern California.
When they did the upgrade they had to test the protection circuits. Interesting video of the line hit with a few short circuits is here. ruclips.net/video/pEL6M27HSVc/видео.html
History video. ruclips.net/video/1BLOqX0Itrk/видео.html
I have had a tour of the Ditmer converter station.
AHA. Thanks for that info!
@@ScottiesTech You are welcome. I was in Jr High, when they started the USA DC intertie. My dad worked at BPA at the time, so I learned of the issues such as lightning, CME, EMP, etc protection the long lines needed. CME protection is needed on long lines running North/South due to high ground currents from Northern Lights. Need the line to stay operational even during a solar flare and high Northern Lights activity. This is much more complicated than run a wire and add two converter stations.
mind blowing. thanks!
Nicely done educative video. Congrats! :) Good to know thing or two about what's up with HVDC nowadays. Cheers!
Great n simplistic talk
Australia has a single wire undersea cable supplying HVDC from the Sate of Tasmania to Victoria, it lies on the sea bed and has been broken at least once. There were concerns about increased corrosion due to electrolysis using earth return over seawater
This is a well presented and informative video. It is well explained to the layman. Another advantage of DC links which is useful for inter connectors is that you can control the power flow direction and magnitude. Another disadvantage is the harmonic distortion but that is very difficult to explain. Australia has a DC interconnector between the mainland and Australia called Basslink.
tasmania!!!
Yes. Thank you. My mistake
nice video
The island of Tasmania is linked to the rest of the Power Grid of Australia through an underwater DC Link.
The link is 230 miles long (370 Kilometres) carrying up to 630 Megawatts at a voltage of 400 kV.
Scottie... beam me up! You da man ! Slightly off topic but maybe not... Dave Stetzer et al. preach about the overloaded neutrals in the ac grid in America. He claims they use the physical ground for a return path, which in turn is making people sick. A dc grid will impact this for better or for worse.
computers and other hi tech equipment have introduced harmonics that overload the system.
Wow. Fascinating to think about. That would definitely have an effect.
I vaguely remember reading that at low voltages DC is "better" then as the voltages rise AC is better and as the voltages rise again DC comes back into its own for reasons such as the skin effect etc. It's complicated but engineers wouldn't be using HVDC if the problems outweighed the benefits.
There is also another disadvantage to HVDC and that is harmonics in the primary A.C. supply. And you also need input line reactors to filter them out.
Wow so these new HVDC lines will cause dangerous dirty electricity
@@flat-earther They can if there are no line reactors installed on the input to filter out the harmonics. You see anytime one alters the shape of the sine wave you create harmonics which are multiple frequencies of the fundamental frequency the triplen frequencies are the most harmful the 3rd, the 9th, and the 15th and so on.
Thanks for the video...how do those DC to AC converters work ?
They are called inverters
@@b-bnt That is really funny....
3:29 converter on the left = essentially a bridge rectifier, Device on the right = inverter. Not identical devices at all.
Except, eg, in NZ inter island hvdc link is bidirectional
*Scottie,* would [emergency] generators (which require fuel) be categorized as DC, or AC? I know they are extremely limited due to the fuel usage.
As I understand, "renewable," or "green energy" sources are actually *carbon fuel extenders.* What are *your* thoughts on that? I wish to learn from the best. Thank you.
Most generators are AC, single-phase. There are some larger 3-phase ones though.
DC arcs will one day light up the world #prophecy
We could simply just go to bed earlier like we used to before the advent of cable
Indeed. Enjoy. ruclips.net/video/pEL6M27HSVc/видео.html They tested the protection by firing small rockets pulling a wire into the substation. Due to the capacitance of the line, this is a very noisy event.
Hi.... What are the advantage and disadvantage ..if I make our exist AC supply to half wave DC?
I am Indian and we have 220V AC, 50hz.
In our trains, we get 110V DC(may be halfwave) to charge our mobile. The trains have this as commuters , specially children meddle with the sockets and prone to shock and electrocuted or whole wiring get grounded whatever...(what I think out of my little electrical knowledge..)
Why use AC power sources when using DC power transmission? Why not make consumers' power be just DC?
We already have DC generator designs, and solar cells are basically DC already. This makes power storage more efficient just by ditching that AcDc conversion.
Plus electronic products are basically DC with ACDC converters. The only reason we are stuck in AC is that consumer motorized appliances are AC powered.
Even appliances increasingly use computer-controlled brushless DC motors!
you forgot plasma losses, which are significant
No ef emf waves around power lines since its DC ?
There are, but they're more static since the voltage and current are more constant.
Would you say that a converter is a.... _FULL BRIDGE RECTIFIER?_
Joking aside, I really enjoyed this video. You've definitely got a Bob Ross thing going on which plays well with my ADHD.
A rectifier is ac to dc, a converter is dc to dc, an inverter is dc to ac, a transformer is ac to ac
Imagine winding a coil with that 0_0
Also aren't the wires of the HVDC stuck together bcs of magnetic force ?
And all these losses increase with the rise with frequency.
2:50 i mean....ok, but what am I even looking at here.
Long story short 4:42
Don't get it I think they made HVAC in the past because of the fewer power losses. Saw an documentary Tesla vs Edison. Now the HVDC is better because of the fewer power losses.
AC has fewer power losses in Transformation or changing one voltage to higher voltage. but AC losses more in transmission because not using 100% of cable and capacitance to ground creating current path so DC is more efficient in transmission at same voltage. Now HVDC easier because of silicon technology which not available back then.
not just the power losses. the AC could be converted to lower/higher voltages much easier with the old technology. they'd just needed a transformer which has no moving parts and can be manufactured with old tech. Very reliable technology. Now with silicon/carbide semiconductors, it's possible to convert DC/DC , so no need for AC lines. Fewer wires, fewer losses..all adds up. They just didn't have the tech to convert DC to DC efficiently back then, so the transformer and AC was the better solution.
Electrons barley moove its the msgnetism who are carrying the power i think
Big mmmmmmmmmmmmmmmm
Please Sir, in the future with the advance in technology, will it be possible to transfer either AC or DC wirelessly and efficiently across the entire globe eliminating the entire usage of cables ? And what could be the challenges that should be overcomed to ensure closer success ?
Theres some work done in New Zealand
techxplore.com/news/2020-08-zealand-startup-eyes-global-wireless.html
I thought ac won over dc because dc couldn’t do long distances
Mostly AC won because with transformers, you can easily bump the AC voltage up which reduces the current. At the end user, you pass it through another transformer which steps down voltage and current goes back up. Losses in cables are due to the current, so if you have DC at a high voltage / low current, you're okay. That's kinda simplified, but you get the idea!
DC couldn’t do long distances because they couldn’t step up very high voltages in those days.
1.1 million volts is …….. pretty high
Your pretty high
K so who is lying here, you or my electronics teachers? Or for that mater, who explanes false? I haven't tested to veryfy long distance HV, but generally a conductor have resistance in it both in AC and DC. And it most notable in DC. Soo what you say here makes 0 sense in that the reason they used AC in the first place was to avoid the large energy loss across the wire due to resistance in the wire cross long wires. Short distance. was no problem, but long distance you got high voltage losses on DC, and that was solved by using AC instead then you didnt get that high loss, as then it didnt need to travle through that much reisistance. (0.02 Ohms or so pr meter in a 1mm copper i think it was adds up the longer the wire to a high resistor) Yet you claim here its the oposite?
More explanation is needed to why that is or is not the case. Does it change when its HV, if so why?
There is always resistance when a current flows through a conductor - AC or DC. The more current that flows, the higher the voltage drop across the resistance of the wire. One of the reasons AC was chosen over DC is because it's easy to generate 3-phase AC and then pass that AC through transformers to bump the voltage way up, which also pushes the current way down. The less current that flows, the lower the resistive losses in the wire. Of course, high voltage power lines can still carry thousands of amps, so you still need a thick conductor.
But since power = voltage x current, transformers let you take low voltage / high amp juice and send it more efficiently over long distances since low V / high A becomes HIGH voltage / low amps at the output of the transformer. Resistive losses also apply to DC, of course... which is why most often, they're taking AC, cranking up the voltage thru a transformer, and then turning that HVAC into HVDC.
Note also that with AC, you have additional losses due to capacitive and inductive reactance, which you can think of as "extra resistance to the flow of current, but only for AC". Even with that added reactance, AC was still favored over DC because the whole system of 3-phase generators + transformers was better all around.
Finally, in the early days, 3-phase AC was favored because it could efficiently be transmitted to remote locations over power lines and then be used (still as 3-phase AC) to drive powerful, smooth, relatively compact motors for mass manufacturing and such.
Have you SEEN how long DC transmission lines are?
Wait... you're not Scottish. I'm outta here.
Blah blah about "Expensive" :D DC-DC step down.. nothing is needed.. our power electronics is already made for it.. ill just leave this here..
ruclips.net/video/_KznsF7VYWc/видео.html