The Most Confusing Part of the Power Grid 

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Hi Grady. As a retired power utility engineer in Scotland, I'd like to congratulate you for such an amazing video that incorporates all the main concepts of the AC power system in about 20 minutes. A lot of former colleagues couldn't explain these concepts as clearly and succinctly as you have done here. Well done!

19:53 Got jumpscared by bearded Grady

I ran a 40 MW generator for twenty years, and was responsible for training many new operators. I really wish I had had this video available. I can’t count the amount of time I spent trying to explain VARs, and why it was necessary to comply with utility voltage orders. VARs are compensated by over or under exciting the generator field. How far to over or under excite comes in the form of a voltage order from the utility. Another problem generators have when exceeding the power curve is heat. The further out you move on the curve, the more heat generated inside the generator windings. A large part of generator design is the centrifugal force of the rotor spinning. The materials can only stand so much before flying apart. Heat weakens the materials making catastrophic failure more likely. Also, wires have their own resistance, and resistors convert current to heat. More current, more heat. You can see this with a little patience. On a summer day, use a tripod to take a picture of the wires between to transmission towers around 2:00 PM when load is highest. Take another around midnight at the same spot. You will see that the wire sags several feet when under high load. A wire sagging into a tree was the initiator for the Northeastern blackout in 2003. It caused a ground fault which tripped a generator. This caused an under voltage which tripped several surrounding generators, which tripped more generators, which cascaded and ended up tripping several states worth of power grid.

Power systems engineer here. This video is a triumph, so concisely covering an astounding range of core power engineering concepts with remarkable approachability. Thank you for doing this public service for our industry.

6:01 Grady trips over and inexplicably acquires an English accent.

When you’re 10 years old and want to be the best developer, but SimCity residents won’t let you because of power plants.

This video explained volt-amps, real power, apparent power, reactive power and power factor better in a few minutes than my instructors did in multiple years.

This (no pun intended) just lit SO many lightbulbs for me. I've only ever tried to think about power factor in an industrial context - not a class or lecture, or any full description of the concept and I've been frustrated that I didn't get it. All the stuff I've been able to find online gives you a pile of equations stripped down for utility and zero intuition for why they work (or even what they're doing). Your animated graph with the power going negative along with the idea of energy being temporarily stored for a fraction of a phase was all I needed for everything to click into place. Now I'm going back to the rest of the internet to see if I can grasp the power triangle better with a new mental model... Thank you!!!

When he connected the polarised capacitor i expected an electroBOOM moment😅

15:05 I was having trouble understanding how generating more power in the system wouldn't help deliver the power but the analogy of a burnout actually helped lol.

That was a really excellent description. And even though it was only in passing, you even mentioned the single most important equation from ohms law... the power-resistance equation (P = I^2 * R)... very few RU-vid personalities mention that equation or even realize that it exists or what it means. So lets expand on it a bit to round things out. This equation governs power lost to heat in a circuit, wire, or cable. As you can see, it is non-linear with current. There are some major consequences to it being non-linear with current: * When you double the voltage you halve the current to make the same power, but LOSSES wind up being only 1/4th. In otherwords, increasing voltage vastly, vastly reduces losses. Not just by a little, but by a lot. * This is why transmission lines on the grid pump the voltage up. If you increase the voltage from 120V to 120,000 volts... so you increase the voltage 1000 fold, you decrease the power losses by a million-fold. 1000000-fold lower power losses. Lower losses == far higher efficiencies. This is why transmitting power over the grid is so efficient. The U.S. grid, on average, exceeds 90% efficiency. * This also works for DC power and is why pumping up the DC voltage leads to far higher efficiencies and lower losses. A 48V battery system is 16x more efficient than a 12V battery system, for example. -- So even though ohms law seems linear on its face, it isn't when it comes to resistance and power. The voltage drop across a resistance (across a cable) is linear, but the power loss is not linear. e.g. 1 amp flowing through 1 ohm of resistance will drop the voltage by 1V. If you are pumping 10V into the circuit (10V x 1A = 10W), you have 9V on the other end and lose 10% of your power to heat. But lets say you want to transmit 10W and are pumping 100V into the circuit? Now you are multiplying the voltage by 10 but you are ALSO reducing the amperage by a factor of 10 to get the same 10W. 100V @ 0.1A through the circuit (10W). Now the voltage drop is only 0.1V instead of 1V, and it is relative to 100V instead of 10V. Thus the power loss isn't just 1/10th, it's 1/100th. Losses go by the SQUARE of the current. * People often wonder why AC wiring has low losses when not under load. I mean, the waveform is constantly switching back and forth and that does mean that there is current sloshing around. The power equation is the reason. Because the current is so low, the losses are even lower. If the current sloshing about is, say, 0.001A then the power losses wind up being I*I*R = 0.001 * 0.001 * R which is 0.000001 * R. * Reactive power only flows along the current path. If HOUSE A generates reactive power, HOUSE B won't see it. But the GENERATOR and all components and cabling in between the GENERATOR and HOUSE A will see it and have to deal with it. * The reactive power caused by a large number of point loads combines into essentially one power factor by the time it gets back to the substation, which the substation can compensate for. Each point load provides its own contribution but they all essentially combine into one phase angle. And there you have it. -Matt

Grady, the retail “return policy” analogy for reactive power is outstanding!

Im an electrical Engineer from germany working in a big Industrial company. We use on site compensating in the low voltage sector (230/400v) which also allows our on site transormer stations to have a greater margin of operation. The compensators are basically just banks of capacitors swtiched on by big contactors row by row to keep the power factor above 0.9 for each transformer individually as here you also dont pay for the reactive power anymore. As most loads are asynchronus motors that dont see rappid switching, these relay stations can keep up relatively quickly. Thing is you can't compensate to a power factor of 1. That creates a resonating curcuit between the load and the compensator and can lead to voltage spikes.

Awesome information as usual! I should quit and let you do electronics!! Regarding 17:03, I would say having just capacitors on power lines works the same as just inductors on the line, in that they also create reactive power and so drawing more current than needed from power lines. So they don't boost voltage, but if more capacitance is used than inductance, the reactive portion of current goes right back up and the capacitors are not helpful anymore. So we need to switch them out/in to make sure they almost exactly cancel out the effect of inductors.

An easy way to remember the phase relationships is: ELI the ICE man. In an inductive circuit (L) voltage (E) leads current (I). In s capacitative circuit (C) current (I) leads the voltage (E).

thank you once again for being our engineering teacher Grady!

In your demo it would be better to put non-polarized capacitor into AC circuit.

Back in high school during the late 1970s we had 2 physics teachers that used simple demonstrations to begin complex lessons. They didn't grade on a curve, 80% of the classes received at least a B grade. When ideas are reduced to their simplest concepts people get it. Another great video making complex ideas easy to comprehend. Thanks Grady!

Excellent explanations! I’ve worked as an Operator at a large power plant, adjusting generator excitation to compensate for VARs as needed by the grid. The best analogy I’ve heard for explaining reactive power is a beer mug: the beer is the real power carried by the mug, and the head on the beer is the reactive power. It isn’t useful for anything, but the mug still has to hold it all!

Nice piece. It brought back memories. Years ago I designed industrial control systems and we had a client paying huge power factor penalties due to some very large motors. (one was 300 hp) We installed a capacitor bank which cost many thousands of dollars (440 system) but their payback was less than a year from lower utility bills.

Making sure that no power bounces back from the load is also super important in data transmission. You can't get a clean signal when there are reflected signals bouncing around the circuit. Instead of power factor you look at the reflection coefficient.

I was a kid when this outage happened and I still remember it. I now work for Hydro-Québec and it's really interesting to see you explain what happened and how it works. Thank you!

After working for 40 years in the energy industry, this is the best explanation of reactive power for laymen that I have encountered. Bravo!

The solar flares we had a couple of weeks ago were as strong as the ones you talk about in this video and we can see that everyone is more prepared as we didn't lose power this time here in the province of Québec.

"...unless you trip over all the cords" Brilliant. Just brilliant. Made my day.🤣

From an electrical engineer who once worked in electric metering: BRAVO. Very good entry-level presentation of this topic. I'm sharing this with some of my non-technical colleagues.

As an electrical technician I truly admire the way you explained the main concepts about AC and Power factor. These takes several years of studying to understand all those things and yet you managed to explain that very simply and clearly. Great job!

16:40 Your picture showed a concentrated solar plant. That power generator does have inertia because it generates steam and spins a turbine, unlike solar panels.

6:13 That type of capacitor is known as an "electrolytic" and isn't meant to have an AC voltage on it. The side with the black stripe marked "-" needs to be negative with respect to the other terminal. If you put reverse voltage on it (as happens 60 times a second with AC from the mains), it can explode and shoot hot capacitor fluid at you. Be careful.

In europe a power factor under 0.85 is deemed unacceptable and the price for reactive power is quite severe. You may even end up paying 2-3 times as much on reactive power depending on power factor

This has to be one of the best videos you've made. It took me a while to understand and work with some of these concepts in college. The mechanical examples are perfectly used and spaced apart to make the video accessible to kids and not condescending to people who already have some understanding.

I have several things i would like to point out I think your battery is undervoltaged, normally your battery should not go below 11.5V, but it could also be a 5 cell lead acid battery which is not common, so i suggest checking and since undervoltage can damage batteries And some mistakes in the video 1. The reason the light bulb got more resistance was not due to higher voltage, but due to the filament getting hotter, most materials when hotter get more resistive 2. Please do not put an electrolytic capacitor in an AC circuit unless you want to be electroBOOM 3. 9:20 is a brushed DC motor Otherwise it is accurate, and i do not expect a civil engineer to know every detail about electronics

Grady, I actually have a recent (couple weeks ago) story related to this. I was having issues with a very sensitive piece of network hardware having issues at a certain time of night each night, and it was related to the incoming power having a fluctuation during the power company's nightly switchover of certain power conditioning equipment. It was extremely difficult to track down, but it was interesting when your video just backed up what we had discovered via troubleshooting. We solved it by using a local power conditioning powerstrip for the sensitive piece of equipment.

16:40 shows an image of a heliostat solar power plant, which uses a steam turbine and itself has inertia, when describing the lack of inertia from solar PV. It's an odd choice in yet another excellent video.

I have worked and played with electronics since I was six, including some years in the power industry. Best simple explanation of VAR I have ever seen.

Hello Grady, You did an excellent job of explaining cos φ (power factor) in a graphical fashion, with the phase lag of 90 degrees caused by a reactive load. The problem of explaining the difference (in AC circuits) between active and reactive power is because power is a vector, not a simple number. This is why I prefer to precede all the explanations about reactive power with a crash course on complex numbers and vectors calculations, together with some basic trigonometry. After just two days of math lessons, every aspiring technician is able to operate advanced power equipment in the power station. The problem of solar coronal mass ejections, is that they induce asymmetries in the sinusoidal waveform, which are seen - across the power lines and the power transformers - as a DC component, which is almost impossible to manage. Greetings, Anthony

This really comes to mind a wind storm that knocked out power to huge swaths of power to my town. You cant just turn everything back on. It takes a lot of monitoring and careful decisions.

Working for a power transmission company and being an amateur astronomer, showing the sun at 656 nm once in a while, this video was bringing together bits of understanding in both fields in a beautiful way that blew my mind (especially the reactive power explaination). Thanks for taking the time to make such good videos.

You have the wonderful talents of being able to explain relatively complex situations combined with first rate media production. It what make your channel so welcome when a new episode is announced. May you have the health to continue for a long time. Thank you Grady.

After 4 years of college i finally understand reactive power.... Why did they only explain it from a math perspective and not explain what reactive was..... it was just how to find it with math and not what it is. THANK YOU GRADY!

I love the before and after. Clean shaven gradey - suddenly becomes 3 days of no sleep and no shave . Good work dude, keep it up. Love the videos, and how simple they are made.

I'm not an EE but I thought I had a pretty good grip on how the grid works. Not even close. I learned a TON from this video. Great work, Grady!

That poor Hulk Hogan ... I'm sorry, Zap McBodyslam ... toy. :D

Excellent video. It's a great refresher of power engineering for my EE / Electric Vehicle Engineering thesis defense. You explained it much better than the professor.

For years I've been aware of all of these terms but never had a really good grasp of what they meant. Today that changed! Thank you so much for publishing this 💜

Great video Grady! Took me back to my AC transmission class in college. Your 20-minute explanation was much clearer and more succinct than my professor's was back then. He did the best he could in the day only using a blackboard.

6:19 Did he really use a polarized capacitor on AC? 😂

*Applies AC to your electrolytic cap*

So far you are the only person I came through who makes good videos on both civil engineering as well as electrical engineering, kudos Grady kudos.

Great presentation accurately explaining many complex concepts in electrical power. Fantastic job explaining fundamental concepts without straying into related topics that might require specialized knowledge.

I didn't realize that Quebec was literally a capacitor

I had always wondered why UPSes were rated in both VA and W, until I learned about reactive power.

I have tried a few times to wrap my head around power factor and reactive power and could never really understand why it was a problem at all. This is the first time its actually made sense to me. Thanks!

One of your best videos of the intricacies of the grid! I worked as a power engineer at a major utility and you wouldn't believe the number of power electrical engineers who couldn't explain clearly what VARs are. They called it wattless watts!

The BEST explanation of VA I have come across.

You should've used The Rock's action figure, because he's the most electrifying wrestler in all of sports entertainment

Hi Grady! Firstly, I'd like to thank you for this amazing and incredibly enlightening video! You truly have crammed a full hour's worth of information into a span of about 20 minutes! Okay so, I only recently found your channel - but being the nerd that I am, I immediately knew that I was hooked. I THOROUGHLY enjoy your videos, your easy to follow explanations, and your pleasant demeanor. I bet you hear that a lot, huh (about your 'pleasant demeanor'...)? I'm really glad that there are RU-vidrs like yourself out there educating the rest of us on so many interesting topics - AND doing it without making us feel dumb, lol... Thanks for what you do, man! 😊

Hi Grady, just wanted to let you know that I love the way you explain many different aspects of engineering. Even complex issues are becoming straightforward thanks to you and your commitment. Greetings from power electronics engineer from Poland! :)

Great video. The only thing I'm not clear on is how on earth Grady used an electrolytic capacitor on an AC power source without the cap blowing up 🤔

I love how every one of your videos feels like you're just casually explaining something you find interesting You're not screaming into a ring light like a boomer at the drive through, you're not condescending, just...explaining. Brilliant.

I wish this video was around when I was learning about this stuff in high school and college. We only learned the math, not any of the theory behind it. This was well done. Thank you.

8:33 this animation explains it so incredibly well!

The Tesla battery in Australia does more for grid stability than it does for supplying backup power like everyone thinks it’s was installed for. It’s insane how much $ they make by just securing South Australia’s power network stability

Where I work there are a bunch of large motors, the power factor is controlled by a large cabinet containing large chokes and capacitors . It keeps the power factor at .98.

Excellent video! As a retired electrical engineer with a power systems specialty, it is always great to see such a clear and easy to understand treatment of a very complex subject. Keep up the good work!

Grady, As a mechanical engineer we had to learn these basic electrical fundamentals, but AC power, reactive power, and all that goes with it never clicked until this video! Excellent job on presentation and practical visual examples.

6:02 Glad you survived! 🤭

Would have loved this when I did my apprenticeship in the early 2000s

I really appreciate how precisely you explain things.

Thank you for all your videos. I’ve come to realize that in every day life sometimes people don’t fully understand concepts and when they are asked questions they really struggle to explain things. Your channel keeps me motivated and excited in the pursuit of long life learning. You remind me how much I love STEM and it helps me push through the daily grind. Keep up the good work.

the solar storm induced direct current into the powerlines,low voltage and high amp this overheated many transformers,i think this information was lost in your explanation.

I have a degree in electrical and computer engineering. I never understood the issue with reactive power. Your graph of power vs voltage and current varying by phase made it all click to me. I wish someone showed me that in school (not that I actually use my degree...)

This video should be incorporated into every Intro to Engineering or other required course at the core of an engineering degree at the 101 level. As many others have said, this is the clearest explanation of a complex subject I've ever seen; I got my engineering degree over 50 years ago, and the partial differential equations I had to learn would have made much more sense with the simple practical examples in this video. Very well done!!

By the way, it wasn't just the SVcs that were affected in Quebec. The impacts went all the way down into the US. Because the sun storm caused an imposed DC bias on the three phases of transmission lines. This caused a huge flow of current in the neutrals of the three phase system. That huge flow saturated and burned out many power transformers. And those transformers take a long time to rebuild so the spares got used up very quickly.

Could you do a technical breakdown of turbo encabulators?

One of the most consistent and high quality RU-vidrs that we have!

One of your best videos! Been in HVAC for 25 years and I dont think ive ever heard someone explain it as well as you did.

Just want to say that this series on electrical infrastructure is an absolute blessing. They are so hard to understand without these animations and explanations.

6:30 - please tell me that's not an electrolytic capacitor.

10 Volts on a lead acid accumulator? That is way too low, you better recharge asap before your accu gets damaged.

You've answered a bunch of querstions I've had for years in this video. Many thanks!

Grady, I love your videos about infrastructure in part because they compel me to think about how complicated and difficult things i take for granted really are. Learning about the complexity of the power grid and the problems and tradeoffs faced by operators and customers gives me a greater respect for a thing i would otherwise just complain about whenever it goes bad.

just a question, why the power in the graph at 8:33 is not zero when voltage is? is there a reason for it or is this a simple mistake?

As an Australian, please don't copy anything we're doing. Our power grid has never been less reliable or more expensive than it is now.

Never stop making these educational videos. I've learned so much from you bro, so thank you.

I wish i had this video a couple years ago when i took my Circuit Modeling class! Good job giving an intuitive explanation of something with a ton of literal complex math behind it

Babe, wake up! There's a new Practical Engineering video!

This has to be one of your more complicated episodes from a math/theory perspective. I really appreciated it!

I could never get my head around this concept until I watched your video. Thanks, Grady!

The more I've learned about our power grid & our climate, the more i realize that modern nuclear energy is our best option. LFTRs, Thorium Reactors, molten salt reactors, etc. Utilizing our advanced technology, Improved engineering & material science. Utilizing our greater understanding of safety & well made designs. We have so much more advanced computer technology & robotics that can be used. It feels like even tho tons of advancement has occurred with engineering designs, safety measures, etc. It still doesn't matter to most people. It's like most people are ingrained with a natural negative response when talking about nuclear energy. It's a bummer because i truly believe that our best option for our future is to start utilizing Modern advanced nuclear energy options in our electrical grid. It's just proving to be challenging to get politicians to get on board. It will really allow places to be much more energy independent. Less reliant on fossil fuels. They'll have efficient, stable electrical grids and the rest of the grid could experiment with alternative power sources, power desalination plants, etc. We need to heal from the trauma of our past. See & learn that those things only happened solely from Us not understanding what we were doing when it came to nuclear energy at the time. We didn't have advanced enough technology, material science, engineering, safety measures, understanding of how to go about everything, etc. This source of energy will greatly help the world improve towards the future and lowering emissions. More than anything else could, while also providing a very stable electrical grid system. Currently we have alternative energy options but the majority of our grid is powered off of fossil fuels and emission producing sources of energy. We will be so much better going forward commiting to modern advanced nuclear energy options. It's been very irritating that our society has taken this "Change is up to you" approach. It just takes advantage of people's emotions. This climate issue is so much bigger than any one individual. This needs to be an across the board kind of thing. That's the only way we might make the Slightest difference. We've already waited too long. Everyday is a day wasted. A day where we haven't committed to modern nuclear energy options. Where we haven't even started building it. It should be utilized in collaboration with other alternative energy sources all over the place. This power source is the best option to improve our environment & will really help lower our emissions. The only thing holding us back is legislation, fear mongering & past trauma that's affected us from our past failures (which is understandable but I know we can do better now. We've learned so much sense then. We gotta give it a shot. It's such a beneficial energy source when done right) Did they outlaw electricity, oil, natural gas or coal when things went wrong in the early days of those fields? No! They kept going and understood things usually are bumpy and difficult in the beginning and kept going even tho those sources negatively impacted our environment. A huge issue is our government is BLOCKING any sort of progression from happening. Will be lucky to see the slightest projects approved or finished with-in the next 100 years.. It's very annoying to see how much we have gotten in our own way when it comes to improving or advancing certain things. Instead we let fear, money, man made "required legal processes" Stop us from doing anything other than wind, solar, oil, natural gas, damming our rivers, mining for minerals... It's very frustrating because we should be able to use all these options in collaboration. If we actually wanted to improve anything. That's what we need to do and stop letting so much potential get blocked from ever occurring in the first place.. It's really irritating. I wish certain people didn't make this so "complicated and difficult" Why would any reasonable person want to block progression?

This might be a limitation of your scope, but 8% of the male population has some form of red-green colorblindness. Including me. So from my perspective those traces are exactly the same color.

This is outstanding! Your explanations of the basics of power engineering are the clearest I can imagine is even possible! Great job, and really interesting video overall.

This explained more to me in 20 minutes than my teachers at school could in a year. Why? Good explaining and actually showing what's going on. Thank yu, Grady!

Grady, captain physicist here. Power doesn't flow. We can't say like that. It's *energy* that flows. Again, power plants also don't produce power. They produce *energy*, not power (technically speaking, power plants only convert one form of energy to another, but for the sake of simplicity let's leave it). So, it's *not* power that's flowing in the transmission lines. It's *energy* that's flowing through them, electric, that is.

For a wireless road that can also act as a power line (burried underneath) what about using an electric car and a personal card/smart tagging whenever someone gets on the road? You can have capacitors (and batteries) always on the side of the road ready to discharge and recharge, with the tires acting as the inductor. What about using homes and cars as a means to buy and sell power from the power grid to other areas, and that way people can not only charge their vehicle, but buy and sell intelligently on the road (literally) - that would open up a whole slew of opportunities for people who own electric cars, in which their batteries become way more valuable than just a fuel tank- adding value to the vehicle they just purchased, turning it into a working investment beyond getting from point A to Point B. The Overall Idea is to get power to flow from Large Areas that Already Have Lots of Power to Rural Areas that Don't, and Might Need Help for Power To Flow To Them, Besides People. People would be able to see the health of the grid in real time, and they could Literally Plan Vacations and Get Paid To Actually Take Trips. Everything would be Seamless with a trip planner and an overview, and they could even be advertised to go on a trip somewhere, Literally to either Buy or Sell What They Own Seamlessly, almost like an Electric Stock Exchange.

One of the best videos I’ve seen, great explanation of the basics of power grids.

Hi Grady, as a power system engineer I think your description of the role and flow of reactive power within the grid is very well done. It can be difficult to explain it to people who aren't familiar with the topic, and I think you have done an amazing job. Well done!

This is one of the best videos I have watched that explain reactive vs resistive loads and other electrical concepts. Thank you!

As someone who sells utility scale power factor correction for a living, I have always struggled to explain to my non-technical children what I do. This video is the best explanation I have yet seen. Very well done.