 This is Guillermo Sabatier, your host for today's episode on Perspectives of Energy here on Tink-Tak, Hawaii. Thank you again. And I am the Director of International Services for HSI, your host. And today we'll be covering the fifth installment of our NERC exam test prep, session five. So this will be a continuation of the last one where we talked about emergency preparedness and restoration. So hopefully we get to work from the very end and work our way back and hopefully we'll kind of cover all the questions on there. So thank you again for the engineering team here at the station and Tink-Tak to help me get through this challenging flipping of slides and presentations. So yeah, without further ado, let's go ahead and get started. All right. So here we have a question and typically you see a question like this in the NERC exam. You see it starts with the transformer is loaded to 150% of its capacity. So it's a bad sign to start with, right? And the only other transformer capable of relieving the loading is at 90%. So even if you happen to share the load between these two, you will still be heavily overloaded, right? If you move it like 140 and 100, it'd be like maybe 120 and 120. You still be overloaded by 20%. And in some cases, you can have a short-term rating. Maybe you could do like a half an hour to an hour, but it wouldn't be worth, especially in a transform. So depending on your company policies for the most part, how should you, how should the overload be alleviated, right? So the answer here is shed load. And that's a correct answer, the most correct answer. However, let's talk about why the other answers are wrong. So let's look at the very first obvious one. So the first worst answer you can think of is remove the 150% load transformer from service. That might happen on its own anyway in a little while, especially since you have a lot of protection in place that controls that, right? So if you go ahead and let that transformer sit at 150%, eventually you might have a, the relaying might take it out for overcurrent. So these are not a good answer. And if you do that, then the other transformer is going to overload way beyond its short-term emergency rating. So that's a bad one. A, another wrong answer is adjust the tap changer on the 90% transformer. That probably will not help you. And in some cases, these transformers usually don't have remote. If it's a distributed transformer, you probably can't do it. So one of the things you want to like talk about is the fact that in this case, you may not be able to, to move those taps anyway, they may be tapped out to begin with. And the other thing is the taps really are to adjust voltages, not really to control the amount of flow going through a transformer. So trying to do that, you're going to, you're going to cause other problems, right? So what's the next one? Raise transmission voltage. So raising transmission voltage, that's not going to help you either because it was going to happen there as you raise voltage, you're going to cause another problem that would be transferred down to the distribution side, right? So that, that will be, that will be much of a help, especially at these levels of overload. So in reality, all you can really do at this point is shed load. And when they say shedding load, either this is probably a distribution transformer, not really a transmission transformer. So in this case, right, it's probably all you can do here, just shed load. So that would be the best answer in this case. All right. Thank you. Let's go ahead and work back up to the next one. It's 39 or something. All right. After a forced outage, a contingency analysis study shows that one more outage will cause a severe violation. There was a parallel line up for maintenance with an emergency return of four hours after requesting. So what must be done first to mitigate this condition? Let's go back and read the question carefully again. After a forced outage, which means a line came out of service without you planning it, it just happened. Either a tree or lightning or something damaged a line that came out of service and it's not going back. So now when you run a study, CA contingency analysis, your study shows that one more outage, meaning that now you're at the, you're at minus one condition already happened. So now you're on to the next contingency. If this one happens, you're going to have a severe violation. So now you're, now you're, you can't survive the next contingency. So this parallel line is out for maintenance with an emergency return of four hours after requested, right? So in this case, right? It's going to take four hours to get that line back. If you can bring it back earlier, you know, it'll definitely help you. That's going to be four hours in this case, right? So you're as concerned here is what must be done first and first to mitigate this condition. So you can't put the line back in service. I mean, it's going to take four hours, right? It's no way. B, put the parallel line in service without protection. That's, you don't, you don't ever want to put a line in service, right? Without protection because of the fact that anything happens and we're not meeting that's like, uh, imagine changing the breakers in your house and putting like a straight wire on both sides. You know, there'll be no protection at all. If, if a short happens, it'll just keep feeding that until it burns down. So you don't want to do B either. And C, take the protective tripping off the line, which also is, is another thing that, that is the same thing, the same thing or a protection of a line is, is never a good idea. So in this case, the first thing you can do here is call the ERC and come up with an operating plan. Here, a lot of things could happen. They can start working towards getting the line back in service, got calling additional approves, maybe doing some redispatching. Either way, it's A, B, or C are not good plans. Um, and so calling the ERC and telling them you're in this kind of a bind is, is really a good step to, to get started. And this is quite a bind. So that's the first thing I would do in this case. Let's go back up to the next one, 38, I think. Thank you. All right. Loads and normally cycle can result in what? Doing restoration. Okay. So that's cold load pickup, right? That's, uh, the answer is C. So what happens with cold load pickup is usually, uh, you have, and here is what throws you off, right? Uh, because load diversity is, is, are loads of cycle quite a bit, right? Right. So, uh, A or B here, uh, somewhat, when you have, when you lose load diversity, um, that's a very difficult one because it was really easy to lean on A, because when you say loads that normally cycle can result in what during restoration, lots of load diversity, I can definitely have it. Uh, but the first thing that you normally would see is cold load pickup because, uh, when you first energize, when you first energize that circuit that's been off for a while, the majority of the load on that circuit, you tend to be, uh, AC synchronous motor, right? Whether it's, it's, uh, uh, compressor for an air conditioner or fans or a heat pump or, or even an air hand or anything else that runs on an AC motor. Those AC motors, when you first start them, they are going to behave almost like a short circuit until they begin to spin and they come up on speed. At that point, they're, they want to feel more of a, uh, eventually load levels off, but that can take as much as like 10 to 30 seconds of being straight. Uh, and that's why cold load pickup made sense. Uh, the load, the loss of load diversity is, to me, having that, that answer, there's a little bit of setting and a lot of might be tempted to answer that one as well instead because, uh, load diversity happens when, when you have, for example, air condition is on a thermostat, right? If every air conditioner is, is, is off during an outage and you turn them all on, they're all going to turn on at the same time, right? So that loss of load diversity will, will happen, uh, during the restoration because of the fact that these, until that homes begin to cool off and you begin to then have that sort of, uh, AC cycling off and on, right? Uh, you, you're not going to get that diversity again. Here, you're going to get every single air conditioner and every single house running at the same time. So that's why it's tempting. So for me, I would say cold load pickup was what happens first and then load diversity happens right after that. So I think the best answer here is cold load pickup in this case, because of the fact that, um, whenever ACs turn off and turn back on, you're going to see, you're not going to have the impact of cold load pickup as much as you would, right? And until you have an hour. And so that's why I always stick with C in this case, even though a sounds really good. All right, let's go up to the next question. A minimum time that a backup control center must be activated to count as a valid test. Okay. So this is on the EOP 008 standard and, uh, they require you to run a test for two hours. So once a year, you got to run your, your, your operating plan on these like back control centers and you have to run the backup site for at least two hours. When you do this, right, you have to be at least, um, for 120 minutes was two hours. And, uh, the standard, you don't use minutes as you use hours, which can really throw you off in this case. So in this case, the answer is C 120 minutes. Now a lot of times usually go a few minutes over just to make sure there's no, there's no, uh, hiccups in the center. I've seen things that an entire exam go, go, go, go badly because they ended up running it for 118 minutes and they were just two minutes shy of running the test because they thought they started two minutes sooner than they, than they, than they really did. So, so normally we usually run it a few minutes after just to make sure we cover the two hours, but the requirement is two hours is about a test, which in this case is 120 minutes. Okay. Thank you. Go ahead and scroll to the next one up. Ah, okay. So here's another interesting question. You are a transmission operator with a system operating limit on line one. Of 90 MBA. So the line one is up, up there, uh, joining both, both of the actual, both of the, uh, is between both of these rain buses, right? So generator one is at maximum output, meaning it all I can give you is 200 megawatts. And it's, it's, it's, it's all I can do for you at this time. Line one and two have the same impedance, right? So line one and line two. Have the same impedance, right? So basically in this case, right? They are the same. So at least here, you know, they, they behave the same. What is your plan of action to alleviate line one? So here you have several options. Now, you notice here that you have a series reactive, right? So, you know that, uh, you're already overloading line one, so they don't want you to calculate all these things. So really what you can do here is, uh, you notice that line one has a series, um, uh, a series reactor bypass breaker, right? So in this case, when it's closed, you basically have bypassed that series reactor. If you open it, you're going to, what you're going to do in effect is limit the amount of current that can flow through that line. You basically have increased the impedance of that line. So if you do that, right? My line two has an impedance. So if you, if you increase the impedance of line one, you are now forcing flow to go somewhere else and you can reduce that. So what I would do is, of course, open the breaker 11, which when you do that, you force everything through that break. Okay. That's that answer. All right. Go ahead and go to the next one up. Uh, uh, hey, a basement fire forces the evacuation of a reliability coordinator's primary control system. How long does your RC have to transition to and fully implement backup functionality? And here's another one where they made it also two hours. So they gave you two hours to not only get from your primary control center to your backup site, but remember, it's not just travel time. You have to get in there, park, badge in, get in, sign in, make announcements and then say, okay, I'm ready to take control at this point. And then you take control. And that's how long that transition time is, is valid. It's not just driving time that they want to measure here. It is the entire transition. That's why it's two hours. There's a pretty handy number because they give you two hours to get from one place to another. They also give you two hours to do the annual test, right? We have to operate for two hours. So we're a pretty simple figure. Hopefully not difficult to find it, but you be surprised how easy it is to take more than two hours to transition from one place to another with only a few miles away. All right. Let's move up against that next one. Your system is in the process of recovering from an eight hour blackout during a screen cold weather. Why is a controlled operation switching strategy preferred over the all open approach? Okay. So you have transmission stations, right? And they all have breakers. They all have batteries. They all have battery chargers, right? The batteries are what they call station batteries. This is usually like a bank of maybe 60 batteries that each have, like maybe like a two, two and a half volts each, maybe three volts and then they give you a total of 120 volts DC. Most of your DC systems in the station relaying trip coils, close coils, that sort of thing, telemetry, alarms, RTUs, remote terminal units, all that communications. All of that relies. The battery bank to operate and they have UPSs, right? So the reason being is that the now the all open approach versus the control over approach means you're only going to open breakers you need to carry out your switching functions and restoration. There are a lot of places what they do is that they'll go in there and start hitting remotely, open all the breakers open, open, open, open, open, open. And then what happens is a time you do that, it begins to deplete the stored energy in the battery bank. So ultimately, unless you're ready to bring power back to that station, because you're energizing a line and a path to that station, I will do a controlled approach here. So that's why B is a correct answer, right? All right. Now B to minimize the probability of making a switching error, actually a controlled approach puts you at a greater level of risk as opposed to the all open approach. If you do the all open approach, you basically open all the breakers in a station and then you avoid accidentally picking up load or or tying into the rest of the dead system. So these these are a good answer. A minimize cold pick up, it doesn't make sense because in reality, you're in a transmission transmission system, right? And in reality, when you do that, you only going to operate the, in this case, you're operating the transmission breakers, you're not really messing with the distribution yet. To expedite the restoration process is probably not a good reason either because remember, everything is supposed to be in reliability, not really about speed and getting it back on, right? So really is what you try to do is preserve the battery power. These batteries are only good for about maybe eight hours. So the longer you can preserve, the better. Now, if you want to do the all open approach, because you have the next station always energized and you're ready to switch that station in and energize the transformer, energize station service, then it makes sense to go ahead and do the all open just to avoid any, any, any hiccups and you're going to have to anyway because if you energize that station, you're likely going to connect it to the rest of the dead system, which is why you want to isolate it. So that's why B is the correct answer. All right, thank you. Let's go back up again to the next one. To be effective, to be effective, not affected during a black condition, RTU should not be powered from an AC source. So like I said earlier, right? Everything runs off of DC source and UPSs. So yeah, you don't see this anymore. You see everything running off a battery station batteries. So for the most part, so you run, for example, everything either a battery bank, DC power source or UPS. So here the here the wrong answer is an AC power switch. And really important thing to read the question carefully is to be effective during a black condition, RTU should not and they put it in bold. You notice you're be powered from and that's of course, you should not be powered from an AC source. That's B. Let's jump to the next one up. So and B is experiencing an operating capacity or energy emergency shall communicate its current and future since conditions to its reliability coordinator. So that's usually when you're setting off an E.E.A. alert as part of the EOP zero four standards when when you for reporting. So here that's one of the sort of the first that's one of the first people you know to fight rights to reliability coordinator and they're the reliability coordinator that decimates that it disseminates that information to all the other B.A.s and T.O.P.s and R.C.s in your region. So the first thing you do of course is talk to your R.C. in this case. All right, next question up. 19. During system restoration, which of the following transmission lines would be the best choice to energize the facility? OK, I think we may have covered this one last time, but it's important to to revisit this. So. So remember doing a restoration process, you are going to have none to very little load. The only load you're going to have on your system is going to be just to balance a little generation you have. So you're not here to restore customers yet. You're here to just make sure you can get generation online and energize their very vital transmission systems to start building your system up again, right? So the characteristics of transmission lines is that. You want to you're going to experience very, very high voltages in some cases. So what you're doing here is to make sure that you minimize high voltage issues, especially since they're all like very, very lightly noted lines. So in this case, a line that's going to produce the least amount of voltage headaches for you is going to be the shortest overhead line, which is choice A 10 miles over the transmission line. Anything is underground or a cable is a giant capacitor is not going to help you. So B is not a good answer. D is perhaps the worst answer because that'll be like the giant capacitor generator. I mean, the giant bar generator in this case, and then a 25 overhead line is also not a great choice either. So the best one here compared to what we're speaking really is a 10 mile overhead transmission line. All right. Thank you. Let's go up to the next one. OK, in the early stages of system restoration, the frequency is 59 hertz, 59.0, which is pretty low. So how much low should the system operator shed to restore frequency of 60 hertz? So again, this is like a rule of thumb application, but it shows up in the test. Usually here is a 6% or 10% of the connected load gives you a 1 hertz relief, 1 hertz improvement in your system frequency. So following that, that particular rule of thumb, chat answer C is the correct one. In this case, that'll give you so and I can remember, right? If you have more frequency shedding load will speed up your system. If you have high frequency, pick it up, load, or slow down your system. OK, so that's kind of what you want to work towards it. So the amount is at 6 to 10% of the connected load. OK, let's go to the next one up. 17. During the initial stages of the system restoration process, low pickups should be limited to what percentage of the total synchronized generation, right? It is important here because there's a little difference and we'll go over it in a minute. Another rule of thumb here is 5%, right? So say you have. You have 100 megawatts of capacity already synchronized in the system, right? Synchronized, you've only picked up like maybe 20 megawatts of this time, but you still shouldn't pick up more than blocks of 5 megawatts out of 5% of it. And that's and that's really the important thing because you can't. It's not really what's remaining in the generator. It's what's the capability and a lot of it has to do with governor control, right? And drew and that's why the 5% is the is the rule of thumb in this case, right? So 5% of the synchronized total synchronized generation. Now you could have several generators online synchronized already for a total of like 300, 400 megawatts of capability. When this case you can pick up 10% of that will be blocks of 20 megawatts at a time. Remember, a lot of that has to do also with the ability for generators to be able to respond to that load. So when you pick up those blocks, if you pick up a block that's too big, you could you could definitely the trip generator on a service because of the fight that you put too much load in the generator too quickly, could respond fast enough and the frequency slowed down the case and then they trip offline because of the under frequency in this case. So that's why you want to limit it. You can definitely always do less than 5%. That if I got probably be like the more prudent thing to do. So if you do like a 2%, you know, that'd be even better. But again, the question here says during initial stages of demonstration, low pick up should be limited to a percentage of total separation, which means that you cannot go beyond 5%. 5% is your limit. And that's what you're asking here in the limit. All right. Thank you. So it's an interesting question. All right, let's go back to the next one. 15. Ah, here we go. Energy emergency alerts. So you just look at your answers working before we do question. You got levels zero to three. So let's keep that in mind. So what these different levels mean. So when you say balancing authority A has implemented rotating black house over native load customers due to a generation of systems. So that means that they're already, they don't have enough generation. What level energy emergency alert would the RC declare for this balancing authority? Okay. So in this case, let's figure out what the different levels are. Level zero just means you're over. You're done. You're back to normal. So you're completely backing out of this whole situation. So things are really good at this point, right? So no, you don't start with level zero. Usually announced that when the whole situation is over. So it's not it. Level one means that you have everything you have available running, but you're still able to withstand the loss of your most severe single contingency. That means that if you have 10 megawatts, I mean 10 units, each of them are 100 megawatts. Well, in this case, your most severe sort of thing is your largest unit, right, that you have on that. So say you have, for example, different generators and one of them is 50, the other one's 500, the other one's 200, the other one's like 1,000 megawatts. Well, 1,000 megawatt unit will be your most severe single contingency. That's why, so that will be the one you need to be ready for. So level one means you got all that, but you can still cover that one loss. At EEA two means you have everything running, but you're now have eaten into that reserve, meaning that if you do lose that largest unit, you will then have to shed low. So you are no longer able to actually run your reserves for your most severe single contingency. That's why it will be a level two, but you still haven't, you still don't have a need to shed low yet. Level three means now you have exhausted all your generating resources and the load just kept climbing. So now you have more load than you have generation online right now. So that means you have to start shedding customer load and that's why you would issue an EEA level three. Okay, I think this is all the time we have for today. I think we actually made it to the halfway point and we made it back as far as we did from last time. So I think we finally met up here. Again, thank you all for today's sessions. We appreciate this. And again, if you have any questions on these exam questions again, I feel free to send me a note, but I also encourage you to go ahead and look at the HSI exam, nerd exam prep program. It's really, really helpful in a lot of cases, right? And if you don't do ours, I mean, at least final one, but I think we're pretty happy with the way ours provides results in this case. But again, just feel free to write me a comment or message and I'll see if I can help you with that. Again, thank you for joining us on this one and we'll join you again soon. Hopefully, I think next time we'll have like some, we'll talk about something different, but I think it was important that we looked at these different exam questions over the last few episodes because I think we definitely get a lot of response and a lot of questions about them. So again, thank you again and have a wonderful afternoon and see you in a couple of weeks.