Why HIGH VOLTAGE DC power Transmission

Why HIGH VOLTAGE DC power Transmission


hi gone transmitting power in DC or direct current can have great advantages over AC or alternating current oh yeah I did try to show you DC was better by electrocuting those animals if it wasn’t for that meddling Tesla and his stupid ways now we would be living in a much better world of DC power line Edison you didn’t know why AC was better back then and don’t know why BC can be better now so shut up in fact even I didn’t know of these so-called high-voltage DC power lines until I heard this guy talk about them these cables are direct current cables not alternating current great science channel check him out I was like is this a joke or some special experiments but then I did some in-depth research and realize that nope it’s real like I said in my previous video Edison was transmitting 120 volt DC to homes from the source which would mean huge currents through the transmission power lines that would limit the transmission distance to a kilometer or two the key success to Tesla’s AC was that using transformers for the same power he could easily bump up the AC voltage way high and in return dropped the current way low and that would minimize the power loss over the wire resistance for very long transmission distances then after the transmission we would just drop it back down to 120 volt AC using transformers to distribute between homes as needed if changing the DC voltage level was as easy as AC we would just stick with DC why let me show you some of the benefits number one every power line is equivalent to series resistors and inductors of the wire and parallel stray capacitance between the power lines or line to ground the longer the power line is the more of these components are added something like this inductor and capacitor this is a filter if I try to measure the AC output using my the power line straight capacitors don’t blow up like that let me just run it on low voltage AC I have a 1 volt 10 kilohertz running through my inductor and if I connect the capacitor to the output you see that at this frequency the output is attenuated and phase shifted by 180 degrees the impedance of the inductor grows by the increase of frequency while for the passes or it drops so the inductor tries to block the AC while the capacitor tries to short it to ground same thing on the power lines the AC gradually gets attenuated to a point that over a great distance almost no energy gets to the other side but for DC there is none of that impedance nonsense at zero Hertz DC the inductor impedance is zero and the capacitor impedance is infinite so all the current that goes in comes out of the other side untouched only the wire resistance wastes power same as AC that’s why in AC power lines they keep them well above ground and far apart to reduce those stray capacitances but in some cases where we need to run the power under the salt water of the sea say between United Kingdom and Europe or underground in the cities the line to earth capacitance becomes huge sucking so much AC power because the wire is right beside earth or water this will waste a lot of active and reactive power where DC doesn’t have any problem whatsoever number 2 DC only transmits active power and there is no reactive power unlike in AC C in an AC system the total or apparent power is a complex number made of two components the first one is real or active power in watts that actually does the work the other part is reactive power which doesn’t do any more can these due to the inductances and capacitances in the circuit let me show you here I have my unloaded microwave transformer connected to 120 volt AC and if I measure the current going in it’s around five and a half amps although I’m not powering anything from it WTF it’s because I’m placing the Transformers primary inductor with around 22 ohm impedance on 120 volt AC so it draws current here I’m also measuring the current using a shunt the current in green looks a bit ugly due to the ion core if you see here the current and voltage are ninety degrees out of phase power is the product of voltage and current when that product is positive we have a positive power which means that we are sucking power from the source and when that product is negative we have negative power which means that we are pushing power back into the power lines so in pure inductors and capacitors where there is 90 agrees between voltage and current the amount of positive and negative powers is equal which means the net active power usage is zero and we only have reactive power now although the reactive power is not a waste the current draw exists and wastes power over all the wire resistances imagine you have to send two amps to do something that only needs one amp that’s four times the power loss over wire resistance my wires and transformer are getting warm as we speak with no output such nonsense doesn’t exist in DC where we only draw active power only the needed current is transmitted number three is the skin effect as I’ve mentioned before if you look at the cross-section of a wire for a see the current is pushed to the surface of the conductor due to the electromagnetic fields the higher the frequency the thinner the skin becomes this reduces the useable wire and increases its resistance and so more waste of power what DC uses the entire cross section which means with the same wire we waste less and can transmit more power skin effect line inductance and capacitance and reactive power draw waste tons of power on AC transmission lines where in high-voltage DC we waste 30 to 40 percent less power number 4 DC lines are much easier to connect to each other unlike AC let’s connect to AC lines together here I have my car inverter running on the 12 volt battery and here I have the city power line both of them are exactly at 120 volt AC that and that’s why you don’t try that at home being 120 volt AC is not enough see the sine wave is coming from the city and the square wave is coming from the inverter they are not the same shape and they are not in phase because their frequencies are slightly different that creates huge voltage differences to connect them they must be the same shape same frequency same phase same voltage level same background same ethnicity and graduated from the same school but for DC we just need to make sure the voltage levels are the same right now I’ve rectified the two sources with a diode and capacitor and we can easily connect them together yes we need to make sure they are the same voltage level and the same polarity of course and of course if we connect them with diodes like this it protects against reverse polarity and ensures that always the highest voltage will go to the output so the voltage levels don’t need to be the same either so considering all these benefits why don’t we use DC all over the place well I’ve already told you it’s much harder to convert DC for such super power high voltage lines at low voltages converting DC is done very easily using the new circuits and transistors like the buck or boost switching converters but imagine doing it at 10 kilovolt hundred kilowatts or a million volts in fact I had to talk to one of my friends Mike Piner who’s a senior electrical technician in a high voltage DC transmission station you see Mike here in his natural habitat among the huge components needed to chip those super high voltage DC lines apart he helped me understand how they convert such huge voltages the bottom line is that at least with the current technology this in-line conversion is more expensive and requires more maintenance compared to AC lines that use transformers especially in urban areas that you need a power converter almost every block now let me show you how to convert AC into DC of course you know that we can use a puny single diode rectifier and I’m using a light bulb as the load and on the scope you can see that the yellow line is the input sine wave and the blue is the output of the diode where the negative of the input is cut off now to make it a DC all we need to do is the connected capacitor across the map I always pick a properly rated capacitor for your voltages now if I connect it in you see that the light goes brighter as the capacitor is helping to keep the voltage up discharging between the pulses are charging with the next positive peak coming in the capacitor here is doing a lot of filtering because the AC component here is pretty large we could also use a full bridge rectifier instead I’m using a differential probe here to measure the output because the input and output reference voltages are different here and you see that the bridge is also flipping the negative wave of the input up and using it and that’s why the light is at full brightness now if I connect the capacitor you see that the light goes even brighter and the ripple voltage is much smaller because the peaks are coming that double the frequency and the voltage doesn’t have time to drop too far now imagine if we had three phases so I have to make my own three phases I had made this contraption before where I’m using a brushless DC motor to turn another one as a generator these motors work with three phases coming in to turn a permanent magnet and in Reverse if you turn them they generate three-phase output here we are if I run the motor we get three phases coming out of the other end the reference point of the three phases is the center of the resistors between the phases now we can use a three-phase even fuller bridge rectifier or EFB are every phase being more positive than the other phases feeds the positive line through the top diodes or being more negative than the other phases gets fed from the negative line through the bottom diodes okay I have my EF BR hooked up to my three phases let’s turn it on see the blue is the output measured by the differential Rome because my voltage levels are smaller the effect of the diode drop is more significant let me turn off the three phase voltages the fascinating thing is that now I have six positive waves per cycle that add up and create my output which is already pretty DC looking without a capacitor now the AC component is much smaller and higher frequency and easy to filter when I connect my capacitor in those high voltage DC centers they kind of do the same thing first off there needs to be three phases coming in then they use a transformer to bump them super high to 100 kilovolt 250 kilo volt or more they also use another transformer to shift those three phases 30 degrees to create six phase AC then they rectify these six phases using the mother of all fullness bridge rectifier or ma FB are also instead of diodes they use something called silicon controlled rectifier which they also call valves they can open and close these scr’s are like diodes that can be turned on using an external signal when the voltage across them is positive imagine these components have to be huge so they can withstand a million volts and carry tons of current rectifying six phases they get a huge DC voltage with a smaller ripple voltage at 12 times the main power frequency much easier to filter and yet they have to put huge capacitors and inductors size of a building to be able to handle the super high voltage and current Wow that power plant is like my makeup I could ride those rectifiers forever too bad they won’t let me in due to liability issues a bunch of kittens anyway of course there will be a bunch of power loss converting AC to high-voltage DC but then you can transfer it much more efficiently over continents until it reaches the next station where you have to convert it back down to AC to distribute they use the same kind of valve circuit and set up to switch the DC back into AC and through a transformer and filter to create a three-phase output of course the created three phases have to be synchronized with the existing power system otherwise explosion that’s why they use the existing three phases to time and switch those huge valves to make perfect signals let me show you how to create AC from DC here I have two switches that are controlled by the same signal and switch the DC input to the AC output if the switches are up they send the forward voltage out and if they switch down they send a reverse voltage out so if it switches back and forth it creates an AC at the output here I made the circuit with ad Walpole twelfth row switch and if I switch it I can create AC and if I make two more of these and switch them 120 degrees out of phase I can make three phase signals and filter them into a nice sine wave now we just need to hire a bunch of underpaid workers to switch these at sixty Hertz high voltage DC lines are currently used for backbone power transmission only but maybe in the future the technology lowers the cost and increases the reliability of DC conversion so that we can use DC all over the place as I always intended get out

100 thoughts on “Why HIGH VOLTAGE DC power Transmission

  1. You need to know that you cant connect your Inverter with the City Powerlines. The Sinus Wave from your Inverter is not a Correct Sinus Wave as you seen in your Skope. If you have an Inverter that makes the correct Sinuswave you need to sync. the Inverter with the City Power otherwise the stronger Power (Citypower) will "kill" the Invertert. We are doing this sync. everytime when we want to work on powerlines without any Voltage but the Consumers need Voltage without any break.

  2. 2:45 those noises shown on the oscilloscope are indicating that Mehdi have the possibility to become Electro/Thor

  3. First love your videos, but i think youre mistaken when you say that ac distribution voltage is 120V. Ive been tought that the distrubution voltage is 12.9KV( in canada at least) which is typically stepped down to 240V at the consumer with a center tap for 120V

  4. Electroboom this might be a dumb question. I understand that its easier to have ac transmited to our home. But why dont we convert the AC into DC when it comes into our homes. It would make it much safer when somebody touches a live wire.

  5. Engineering universities have for years now been talking to students about power transmission going to DC, thus doing away with reactance losses. The utilities seem to think that the cost of changing the DC to AC at sub stations is worth the cost now that large, high power semiconductors are more economical. The problem, however, is in electrical storms. Those semiconductors will get blown out more easily than stations having what is already AC doing directly into transformers, which are more robust than semiconductors.

  6. The future is Modular Multilevel (Voltage Source) Converters or MMC VSC…
    Google it…. there are also two variants, full (4 IGBT’s) or half (only 2 IGBT’s) bridge VSC converters. The possibilities they provide is nothing short of magic 😀 and their application limitless.

  7. why do we need a high-value capacitor in six pulse rectifier?
    we already get pure dc wave in output. so capacitor makes an unwanted loss.

    I think we have mostly inductive load so we don't need any inductor, load itself filter pure dc

  8. Long story short, AC won because of transformers. Not because it is actually better at transmitting power. Transformers meant that it was easier to step up and down the voltage. It is much more difficult to step up and down DC.

  9. The UK national grid has four interconnects which allow importing and exporting electricity internationally. These are used when UK electricity demand is significantly different to the demand of the connected country; or when the current price of electricity in each country makes it beneficial to trade electricity.

    A 2,000MW interconnect to France. 4x 500MW high-voltage direct-current cables between Sellindge (near Folkstone) in England and Les Mandarins in France. The cables are 70km long, with 45km of that under the sea. Began operating in 1986.

    A 1,000MW interconnect to the Netherlands, consisting of one 260km high-voltage direct-current cable between the Isle of Grain in England and Maasvlakte in the Netherlands. Began operating in 2011.

  10. Thank you crazy hairy guy on the internet, i learned quite a bit from this that should prove helpful in the future. just a few more months of saving to get my project rolling.

  11. At 42 senconds, the "DC" Cable photo are AC. 3 phases on each side of the tower for two AC lines. I live near the West Coast DC intertie in the USA running between the Columbia River and near Los Angeles California. Here is a photo of a DC tower. http://i158.photobucket.com/albums/t106/OnlyObvious/Desertec/Path_65_P0002014.jpg

  12. Can you explain what is happening to reactive power which was present before rectification of a c power and also source of reactive power at the receiving end as dc will have only active power and ac has both.

  13. also, even when no reactive power, AC transmits power effectively only 50% of the time. So double current is used, having 2 times more voltage drop and 2 times more power losses in the line.

  14. Sir i am your big fan
    Sir i have an idea can you help me on it
    All the inverters chenge dc to ac using degital signal.
    But can it possible to introduce a valve to cantrole signal and these valves can be cantroled using a specialy dezines 50 to 60 hz small ac generator drived by a dc motor
    Sir please help me.
    I am waiting for your reply

  15. Excellent video, I just had to make an presentation of Lines in HVDC, this video help me a lot. Greetings from Colombia

  16. Can we connect a battery at a float voltage of 13.2V with another battery of 14.2V in series and as well as in parallel? Does difference in float voltages creates mismatch?

  17. That's why solar panels for homes don't give power before they sense power from the main. They have to match the sinus to match.

  18. Why HVDC? Because DC is vastly superior to AC and the only reason we are using AC at all is because of all the legacy crap which isn't compatible with DC.

  19. I hope edison is in hell plugged Into a huge AC current until the end of time. He was a scientific hack and a kleptocrat lackey. He didn't invent the light bulb among other things; his research team did that and he stole their work.

  20. What about a video on a (grid tie inverter) used in solar aplacations.
    Grid tie Inverter does what you are explaining about matching AC.

  21. Should come to Germany. Here almost every home has three phases. So you can use an EVEN FULLER BRIDGE RECTIFIER every day!

  22. Funny thing with DC distribution is that it doesn't only make sense for long distance transmission.
    But some data centers also use it internally. It mainly saves on power supply costs since they suddenly don't need their own power factor corrector. But it also saves on wiring costs due to reactive power not introducing extra power losses in the cables. Then a 200-450 volt DC power bus is super simple to connect to a UPS, all one needs is a big freaking boost converter, or just connect lead acid batteries in series directly to the power bus (diodes and fuses still in line with them), their discharge curve is fairly flat, and most power supplies can operate from 350-130 volts DC.

    Then the data center would have a big bridge rectifier and power factor corrector unit before being connected to the grid.

  23. I had to watch one of those compilation videos the other day of you saying FULL BRIDGE RECTIFIER!!! then I watch this today and I get exactly what I wanted.

  24. DC power is used for electric passenger trains throughout pockets of Europe. Including the UK. So I'd assume rail service companies would be a consumer from those DC power lines.

  25. There's an HVDC power line not far from where you live, Mehdi. It originates at the Arnott Substation in Delta and goes under the Strait of Georgia to land at another huge substation in North Cowichan.

    At 5:48, I was fully expecting a phase-to-phase short circuit, and I wasn't disappointed.

  26. You're thinking of this all wrong man.

    Just have a motor at the right rpm flipping all 60 switches in a circle sequentially…

    Is there a circuit that does this or would a mechanical solution actually be better at these immense levels of power?

  27. 2:57 it isn't capacity it is magnetic flux resistance. It's electro magnetic force interactions and leaking into the athmosphere and also ground by way of magnetics and conduction. I should probably add I'll finish the video tomorrow. He probably gets to that.

  28. You have know the aluminum smelting industry ? 😁 the pots? Pot voltage? . DC 1500v 45000 amps , depending the number of pots

  29. One other advantage of HVDC for grid interconnects is that they also function as an asynchronous tie allowing the interconnection of two AC grids that would otherwise be incompatible because they operate at different frequencies, this is particularly important for grids that would otherwise be isolated due to the frequency mismatch with all of their neighbours. With the move towards more renewable generation it is only becoming more important for grids to work together as different grids have access to different natural resources for power generation and variety helps to balance out the individual fluctuations.

  30. This total negates the fact that AC is still a useful technology in it's own right. 3 phase AC motors power the world, music equipment processes AC signals, and several other things. Is the power loss really that much on AC transmission that it would make more sense to employ those expensive DC conversion systems and also require an inverter at every house/factory for AC? I can't see how.

  31. I wish I knew as much as you about electronics. I would build so many things! I've got ideas and like to make things but I'm not as electrosmart as I want to be.
    Like your videos! 🙂

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