 This is your host, Guillermo Salvatllian, and I'm Prospective on Energy, and welcome to Think Tech Hawaii, and today we are going to talk about power system fundamentals. Again, I'm your host, Guillermo Salvatllian, and Director of International Services for HSI, and very happy to be here today as your host and presenter. And once again, thank you to another great installment and show on Prospective on Energy brought to you by Think Tech Hawaii. All right, so noticing there's been a lot of questions regarding understanding the power system with a bulk electric system or the grid, for example, and how those fundamentals work. And a lot of cases in these discussions get to the point where the way it operates gets a little mowed. So we're going to go ahead and kind of cover some of the basics. Maybe this would be part one of two, perhaps. Oftentimes this can get a little bit more involved. But hopefully here we'll get some common terminology determined, and then hopefully after watching this video, you should be able to have a more productive conversation when it comes to discussing topics regarding the grid and some basic knowledge. All right, let's go ahead and go to the next slide. All right, so for the most part, right, when we talk about generation, and this is a slide from a previous show we had on grid-forming inverters and solar sites, right? And this really came out of the discussion regarding the deployment of solar facilities and wind and all sorts of renewable resources to generate power. The problem arises when you begin to lose a lot of what they call system inertia. And ultimately that loss of system inertia has a really negative impact on grid reliability. And we'll get into why that happens. But what really forms grid inertia is the synchronous generators. Normally you have, for example, it's this rotating mass. I'm sure most of you have seen a typical generator that you buy at Home Depot or at Lowe's and you use that to basically power an RV, power some appliances in an area offsite or off-grid where you don't have any power. You'll notice that that generator has a very heavy piece of machinery and it has a motor and a generator coupled together and that is what most of the weight is centered on. So as this thing is spinning, it has inertia. Well, you can imagine how much inertia all this rotating mass has when you have a much larger piece of equipment, right? Maybe several tons. So as this spins at a certain speed, the synchronous speed, right? Usually it'll rotate at, oh, final output really is 60 times per second, which usually is about on a very simple machine is 3,600 RPMs, revolutions per minute. So something that heavy spinning that fast is going to be really resistant to change, specifically to be slowed down by load. Now the reason that generator spins is because it's connected to all this machinery that has a lot of input on it, which is usually fuel or steam or it's coupled to what, for all intents and purposes, is a combustion turbine or a jet engine, really. And that jet engine usually is always spinning on its longitudinal axis, longitudinal axis. So to make changes on that, to make it spin faster, you have to introduce more fuel, more prime mover, for example, whether it's steam or fuel. Now to slow it down, usually it relies on the inertia and then that'll introduce a change to arrest that drop in frequency, right? Okay, so for the most part, right? The majority of these, of the grid had all these generators spinning together. And usually they were pretty resilient when it came to managing a fault in the system. And when I say a fault, meaning I'm not talking about small distribution faults that you see down in your neighborhood when a tree branch hits, for example, a conductor, I'm talking about those big transmission systems where they have a fault on there where it's lightning or something gets up in those large conductors. Those transmission circuits, a fault on those can have a more of a significant impact on the grid. So these units that are all spinning, I'm talking about thousands of units all tied together through the grid as they're interconnected, spinning at the same speed, spinning at the same phase angle, meaning that they're all linked together all three phases, they're going to be synchronized. And that synchronicity is what allows them to be able to, A, have the correct frequency, 60 hertz in this country, but it also allows them to be able to sustain maintain that frequency at that speed, but also be able to sustain these faults that have happened throughout the grid and not have a problem with stability in as much as one event at a time. All right, so let's move on to the next slide, I think here. And we're talking about what's happening now, right? And a lot of these like generators and a lot of them, of course, we're being fueled by steam, meaning it's generated by burning of coal that heats up the water, creates steam, a sort of thing. So that initial fuel source is what is causing a lot of the environmental concerns and these policymakers, right? So then they're going ahead and they're pushing for these early retirements and some of these plans that still have a viable life and they haven't even been fully, fully, so we're looking for tax purposes when they've been fully depreciated. So they still have a functional life and they still have an accounting life left in them. So they go ahead and retire them early and they replace all that with renewable resources. A lot of things that do not have inertia. We'll talk about what that looks like a little bit in the next couple of slides. Go ahead and go to slide number four, please. So on here, we're looking at the, basically the system breaks up into three different, three different sections of it, right? You have on the left here generation, which is basically all your generators that are tied together through the transmission system, right? Now here we only have a transmission system represented by one line and two transforms, but in reality, this transmission system is spread out and tied together throughout the entire, like Eastern and the connection, for example, and I'll show that map later, but all this transmission system really is tied together and different voltages, right? The transformers usually make that change, but they're all tied together and there's thousands of generators all tied to this transmission system. And then of course, feeding your customers, how do they finally get to your customers, right? Well, this transmission system eventually feeds different distribution systems throughout the grid and the distribution system is what distributes this energy that was initially generated by the generators. So again, it's generated at the generation sites, thousands of them. They're interconnected at the transmission level on this transmission system that is interconnected throughout the whole Eastern and the connection. In the U.S., there's three major sections, right? The Eastern and the connection, Texas, ERCOT, and then there's WEC, and I'll show that map later. So this transmission system is vast, one of the largest machines that were devised by humans. And then fed off of different portions of the transmission system, we have transformers that step it down to distribution voltage levels that then eventually bring that power down to the customers. All right, so let's go ahead and go to the next slide. And here's a simplified view once again, right? Well, you see the generating station in black, those usually are, that's just one generating facility. You can have four, five, 10, 20 generators in one facility, or you can have a smart generator as one site, but you can have hundreds of these, maybe thousands throughout the country, right? Then they are connected through the transmission system where it can be at different levels, where it can be 765,000 volts, where it can be all the way down to 138,000 volts, right? By the way, these are all interconnected, and they connect through transformers in different stations. These are the ones that are usually the really big eyesores out there where you have really, really big structures and really big lines, and they tend to be suspended a lot higher than your distribution circuits. Now, tied to all of these different segments in the transmission system, you're gonna find, for example, distribution stations, right? Where they take the voltage from the very transmission system and they step it down to the distribution voltage level, and that's what finally gets distributed to either the industrial customers or it goes out to the neighborhoods, and these are the ones you see out there, typically you see that out there in your neighborhoods, and eventually that gets stepped down all the way down to your house, where it's going to be either 120 and 240 to power the actual circuit, and that's usually what is delivered to your house or to your place of commercial business in most cases, right? And that is, and I'm not sure what the system looks like, it's very, very simplified, but I guess a lot more complicated than that, right? Next slide, please. So what we're looking at now, right, is that you have all these different, you see different systems out there, and I guess when you look at it on that diagram on the far, far left, you have, for example, generators, which those circular diagrams are on there, and then they're all tied together with those straight lines, perpendicular lines, those transmission lines, and then those other smaller lines that are kind of shooting out like branches, those will probably look more like the distribution system, and that's kind of what it looks like in a nutshell, right? Very simplified, and then with a couple of like renewable resources, and then when you look at, for example, those different little branches where they kind of look like, you know, those houses, right, as they branch off from a main circuit. They're oversimplified, really. What's happening now is that you're seeing a lot of these resources where they're getting rid of the baseload generators, and they're installing all of these inverter-based resources, which are solar and wind, and what happens there is that you're seeing a bit of a challenge when it comes to maintaining system inertia and surviving, for example, faults on the system. So eventually you might see a lot of rooftop solar that's coming, and it's been coming for years, but it still doesn't take away from the problem that the reality that we're newly system inertia and we're going to have to make that up with software, and that can only go so far, right? So next slide, please. So here we see the interconnected systems of North America. You're gonna see here the eastern interconnection, which is comprised of those multi-colored maps where you see Florida all the way up to the MRO, SPP, and New York, and parts of Canada. So that is the largest interconnection, and all of that's connected together electrically. So ideally, if you plug in a load in South Florida, it should be the same frequency, same phase angle, as load up there, and like for example, Maine, for example, New York. So that is the eastern interconnection. And down in the middle, you have Texas, which is an ERCOT, and they have their own frequency, their own separate tie lines. Now, they're all tied together, something they call DC ties, so they don't really share frequency. They're, for all intents and purposes, isolated from each other. And in the west part, you see the western interconnection, WEC. And that one also has its own frequency. Now, mind you, all of them operate 60 Hertz, but you should be able to travel on any part of the country and be able to use your same appliances. But they are all at different frequencies and different phase angles, and they're all separated from each other through DC ties, meaning that they're not going to be operating at the same frequency. And DC ties is probably a topic for a different day. All right, so the next slide, please. All right, so within each of these areas, and you saw before the eastern interconnection, you had different colored maps or regions. You can pretty much think of those as areas A, B, C, and D, like we see in this diagram here. In a lot of cases, though, you will see some of these are tied together. A is tied to B, is tied to D, tied to C. D is tied to all three of them. And then here, in this case, all of them are tied to each other, apparently. There are some cases where some are not tied to the others. It all depends on how their transmission system is interconnected, right? So the thing is, you don't get to remember that, there's flow, powerful moving from one side to the other, depending on how they determine buying and selling a power at a wholesale level. So A, B, C, and D are all possibly different power companies on different regions. And the whole point here is that in there are some cases where some companies will decide to buy power from another company because they just can make it cheaper during that time of the day or that time of the week. That's the case, you know, let's say for example, say B wants to sell power to D, well, and D will then decide, well, I wanna show you X amount of megawatts, then D agrees to buy it, then what will happen is at that point in time, on top of that hour, D will back off from producing that exact amount of megawatts they're gonna buy, and then B will go ahead and over generate the amount of megawatts they're gonna sell, and then they keep doing that for that one hour, and then power will flow from B to D for that hour, as far as that excess generation being generated by B, and then they have a deficient generation in D that's being supplied from a transaction that they're getting from B, and that is an example of interchange scheduling where they're buying and selling power between companies and they find a path to sell that power through to get to the other side, right? Now, the whole point is that all of this has to balance out, you just can't have one power company decide, well, I'm gonna generate less and less and less power every day so I can keep taking power from my neighbors, but ultimately that won't work, that's gonna have a problem, and you're going to have an issue with an advertence, you're gonna have an issue where you're eventually are burdening the rest of the power companies around you, that happens, then eventually they all have metering, they all have, and they're tied, so they all know who's buying what and who is on what schedule, so they wouldn't be able to get away with it for long, and in fact, if they do that for too long, meaning minutes or maybe up to an hour, they will eventually have to pay that power back, that's known as an inadvertent payback. Now also, managing all this frequency, making sure you're on the same frequency, making sure you're on the same schedule, meaning hey, I'm supposed to be selling X amount of megawatts an hour, well, I'm gonna make sure that I am selling X amount of megawatts an hour, so that error is calculated, so that is known as area control error, there's a formula that goes along with that that determines how much power is bought and sold, and how well you're doing with your system speed, that you're going too fast, that you're going too slow, or you're going just at the right speed, like everybody else should be, and that also helps determine your error at that time. And tie line bias, of course, it looks at, basically it looks at your ties with all your neighbors to make sure that you're both looking at the same meters and you're both agreeing to the same schedule, right? All right, let's go ahead and go to the next slide. So the whole point here is, right, when we talk about inertia, is think of it as inertia on the power grid really means you have strong connections with each other, right? If you have a strong rubber band being tied to a bunch of cars pulling up a hill, you're gonna have, for example, the ability to be able to resist some of these changes where it's not gonna pull too far behind or snap. The other thing that's important as well is that if you have strong rubber bands going up this hill, when you're pulling it up, they're not gonna stretch out so far either, and then when you pull really dramatically, they're gonna stretch, and then they're gonna sling back, and then you're gonna have some of that weird oscillations that take place. So that also means stability. So considering that, think of it as a, think of many cars tied together going up a hill on cruise control. The moment you begin to, and they're all pulling this giant trailer, and the moment you lose one or two of those cars, the other cars are gonna slow down until they're able to put more fuel into the system and amp their power up to be able to make it up that hill. Well, that is what they mean by system inertia. If you have the cars moving up at a good speed and they're heavy cars, and they lose one car, well, they have enough inertia to just keep them going up that hill, but they will begin to slow down slightly. So the amount of fuel they gotta put in to maintain that speed going up hill is gonna be a lot less than if they were a bunch of smaller cars, really running really hard, and then dealing with stuff, like for example, like other devices that don't quite really respond to what it changes, right? So the whole point here is that solar doesn't add much to system inertia, and that is the challenge that we're facing. Next slide, please. So a typical generator, right? You look at this here, you got two generators. Ideally, they're on the left, they're balanced there at the same angle, meaning phase angle, right? And they're at the same frequency. What happens there is that if you have a generator that has a problem with either odd, the frequency begins to lie, they go too fast or too slow, eventually that rotor angle will become a little bit different from one to the next, right? And the problem with that is that then as you change your rotor angle, it's not, the system isn't quite balanced, and then that is reflected on the output at that point in time. With respect to the other units, the other generators are on line of the system. So what happens then, then it begins to impact. If a generator goes off balance, then it begins to impact all the other generators in the system. They begin to try and swing back and forth, and ultimately that could cause a problem with stability. So when you have more generators tied together and they're all the same angle, they're all the same frequency and same phase, for them having a disturbance is barely even, it's barely even noticeable. But when you have a lot fewer generators and a lot smaller ones, then any kind of disturbance becomes felt throughout the entire system, and then recovery becomes a lot more of a problem. Let's look at the next slide. Okay, so in this case, stability, right? So when you have an event that happens, usually you're gonna have what they call a damp oscillation, in this case where the system will eventually recover because it has enough inertia. You see initially, for example, it takes a hit, it slows down, and then it speeds up a little bit with a fuel or then it overshoots, then it slows down again, because it holds back and so eventually it gets back to their steady state position and then things are nice and happy again, right? And the next slide, however, you have instability, you're gonna notice a rotor angle where you begin to, if you suffer a fault or like a severe loss of a unit, you may not recover and then you eventually become undamped and your system does not settle back in that steady state position and then eventually you lose stability, you lose other generators and then you can eventually lead to a blackout, right? This next slide, 13, an example of a condition, unconditionally stable system is one that theoretically would not trip and then it wouldn't rely on frequency from other systems, it would just basically be feeding itself but when you're conditionally stable, in this case, if you notice, you're okay on the left end, but it takes just, it can take only so much on the right end until finally it kind of goes past that knee and it collapses. And here we go to the next or last slide, slide 14, please. This is an important slide to consider and I think probably the most important slide for everyone to look at. Here's an example of what it looks like to have, for example, your base load generation and you have, for example, your load and you have your reserves. When you look at the very bottom of the graph, you have, for example, time versus output generation and then of course that green, that blue line up there is your load, your forecasted load, right? So as you notice, right, you have 2 a.m. all the way to say, for example, close to a 24-hour period right here and it's broken up into increments of two hours. One of the things you look at is that you have unit one, more likely a nuclear plant, for example, is running at the same level all day. Unit two is also running almost the same level, but you notice at some point at our midnight, you'll see that that load begins to get into that particular output of unit two. What does that mean? It means that unit two is going to have to back down in this case. Problem is unit one, for example, is probably really, really cost-effective and very difficult to move, especially like a nuclear plant. Unit two, more than likely, is like a very large fossil site, like maybe a coal plant or something like that, of the sort. Units three and four usually are units that are for the most part highly dispatchable. Units that can basically back down and those are usually run by natural gas and that sort of thing. Now, above all that, our units either have to either put them on, put them off, turn them on, turn them off, or they could do what they call load following when those need to be able to be dispatched. Mind you, as the more dispatchable the unit is, the more expensive they are for every unit of energy to operate. Also, shutting them off, shutting them down also costs a lot of money. So why is this important? We notice between the hours of 10 and the hours of four in the afternoon, you see those loads begin to dip down and a lot of that has to do with the fact that a solar energy comes in and it forces units to back down, which is fine as long as we're accounting for that and we understand that we have excess capacity. We also have to maintain that spinning reserve. Ultimately, and the reason you have spinning reserves to be able to manage for the loss of any one of these generators. Because ultimately if you lose a generator, say if you lost unit three entirely, that entire stack now drops one level and then you have to be able to manage, not just supplying your load, but also being ready to survive the next unit you would lose. So this is the problem that a lot of us are having where it's the fact that a lot of these units at unit one and two are the ones that provide a lot of system inertia and so does unit three and four. As you get into more and more solar, that dip in the middle of the day gets deeper and deeper and now you're forced to begin to back down units at unit two and eventually units at unit one, which is really, really precarious for the grid reliability. So if you have an outage during that time of the day, you're less likely to survive as opposed to six, seven, eight in the morning or eight, eight PM at night. So that's the concern. And the next slide, please. And here this is from a previous presentation we have, but you're looking at how, for example, you're losing system inertia at a dramatic rate. And that's something that I think we're going to have to be looking at. So we shall see how that transpires, but hopefully this has like a very basic fundamental of a generation inertia and interconnected systems. We'll get into this in a later topic. But again, if you have any questions, if you have any comments, please feel free to put them in the comments below the video, which I might best get back to you. And once again, thank you so much for attending today's session on Power Access and Fundamentals. And hopefully we'll see you on the next part of this Continuing Education sort of series of grid educations. Thank you and have a great day. If you liked this show, why don't you give us a like or subscribe to our channel? Thanks so much.