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

Channel: ElectroBOOM

Views: 2,495,482

Keywords: educational, electrical, ElectroBOOM, science, electronics, engineering, entertainment, equipment, measurement, experiment, mehdi, mehdi sadaghdar, arc, mishap, physics, Sadaghdar, test, tools, circuit, funny, learn, shock, spark, discharge, high voltage DC, HVDC, transmission, power line, convert, conversion, AC to DC, alternating current, direct current

Id: DFQG9kuXSxg

Length: 13min 2sec (782 seconds)

Published: Wed Oct 10 2018

Reddit Comments

[u/ShadowEntity]

M.A.F.B.R. is my big take away from this video.

[u/Vladi8r]

Fuck i love this guy and his caterpillars. They protect the brilliant mind of his.

My 4th year apprenticeship had a couple chapters that covered this, and hearing it explained without needing memorized for a test gives it the relaxing vibe. Lets me rewatch and rewatch so i can get the concept... not the pressuered memorize this word for word, to pass the test.

[u/odvifnmo]

Ho do you call this 12 phase rectifier? https://imgur.com/MaBc1cP

[u/Fairazz]

I love everything about this guys videos, except that he makes me feel stupid. I would love to be able to follow along better.

[u/[deleted]]

I've always been a huge Tom Scott fan and a huge Electroboom fan. Forget about that DC plant being Mehdi's Mecca, this video is now my Mecca

[u/MILLERRRR]

very long line AC losses can also be addressed by various Flexible AC Transmission Systems. Much more cost effective to modify existing assets with series compensation rather than rebuild as HVDC.

[u/avlas]

/u/melector you damn electrical people using j for the imaginary unit and triggering mathematicians all over the world!

[u/[deleted]]

He forgot to mention the best thing about high power DC..... The amazing arcs!

[u/archermm]

Great video! Makes me wonder the technology behind inverter generators.