Introduction to Electrical Transformers | SaVRee 3D | Skillshare

Introduction to Electrical Transformers

SaVRee 3D, saVRee.com. Where engineers go to learn.

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31 Lessons (2h 35m)
    • 1. Course Overview

      1:25
    • 2. Current Flowing In A Conductor

      2:19
    • 3. Faraday`s Law Of Electromagnetic Induction

      2:29
    • 4. Mutual Induction

      2:47
    • 5. Basic Transformer Theory

      3:06
    • 6. Magnetic Leakage

      0:33
    • 7. Efficiency

      1:05
    • 8. Power and Power Loss

      6:55
    • 9. Transformer Operation Under No load

      0:36
    • 10. Turns Ratio

      0:48
    • 11. Voltage ratio

      4:32
    • 12. Step-Up And Step-Down Transformers

      3:18
    • 13. The Grid

      2:40
    • 14. Transformer Designs

      2:46
    • 15. Dry Type Transformer

      3:27
    • 16. Hermetic Transformer

      5:33
    • 17. Conservator Transformer

      4:43
    • 18. Transformer Cooling

      12:06
    • 19. Transformer Core

      3:19
    • 20. Transformer Windings

      6:32
    • 21. Dehydrating Breather

      9:06
    • 22. Oil Level Indication

      4:45
    • 23. Temperature Indication

      6:32
    • 24. Gas Actuated Relay

      10:49
    • 25. Load Tap Changer

      4:04
    • 26. Off Load Tap Changer

      5:22
    • 27. Transformer Maintenance

      9:06
    • 28. Transformer Killers

      4:11
    • 29. Final Thoughts

      0:40
    • 30. REFRESHER LESSON: Transformer Parts and Functions for courses

      26:54
    • 31. Why Are Transformers & Generators Rated In kVA And Not kW

      2:54

About This Class

Ever wondered:

  • How does a transformer work?

  • How does a Buchholz relay work?

  • How does a silica gel breather work?

  • What does ONAN mean?

This course will help you answer these questions...and many more!

The course is designed to take you from zero to hero concerning electrical transformer knowledge. Even if you already have some electrical engineering knowledge, this course will serve as an efficient refresher. Whatever your level of understanding, I can guarantee you will have never taken an engineering course like this one (trust me, I am not exaggerating)!

Interactive 3D models are used extensively to show you exactly how a transformer and its components work. I strongly recommend you checkout the free preview videos before signing-up (Transformer Components section).

The course is packed with 2D images, 2D animations and 3D animations.

Written content has been read aloud so that learners can 'learn on the go' without needing to watch the screen (useful for the theory topics). 

English is not your first language? No problem, we added closed captions to ensure you don't miss anything. The captions are not auto-generated, they were created by a real person!

In addition, you can visit Trafol.com to actively manage your transformer asset...for FREE!

Regards,

Jon

saVRee.com

Transcripts

1. Course Overview: unless you're living off the grid, you're using electricity from an electrical system that uses an electrical transformer. Power stations use electrical transformers to increase voltage substations. Use electrical transformers to decrease voltage. If you are in a smartphone or a laptop, then you also own a battery charger. This battery charger is nothing more than a transformer. But what are transformers? How do they work and why do we need them? In this course, you learn all of the main components that make up a transformer. You'll learn how transformers work. You'll learn how each of the individual components work, such as the book, all two relay and silica gel breathers. You'll also learn why we need transformers in the electrical grid. Aware transformers are installed in the grid. The course uses interactive three D models to show you each of the transformer components in detail. We'll use images and animations so that you can see exactly how each machine and component works. So if you're training or working in an electrical engineering industry or capture in a related industry such as power engineering, Either way, this course is ideal for you because wherever this electricity and electrical transformer is not far away, hope see you on the course 2. Current Flowing In A Conductor: current flowing in a conductor when current flows for a conductor in the electromagnetic field is created. If the current flow direction is known, the right hand rule could be used to determine the resultant lines of magnetic flux. The blind A nation's shows that if you were to grip the conductor in your right hand, your thumb would point upwards, indicating the direction of current flow. Positive to negative. And your fingers would wrap around the conductor, indicating the direction of the magnetic field north to south. Notice that the blood animation shows that the magnetic field is orientated perpendicular to the direction of current flow. So let's see what that actually means. Concede the conductor in the middle of the screen that's represented by the vertical gray line. And if we were to grab the conducted with our right hand on point out thumb upwards, that would indicate the direction of current flow on our fingers would indicate the direction of the magnetic field, and that is north to south. We go further down weeks. Another image, if current flows through a conductor that is coiled, the magnetic field created, can be represented by the below image that's this image here, we can see that the current is flowing in. It's going through this coil That's a coil conductor just referred to as a coil or a winding. And the result magnetic field created is represented by these flux lines here on here on both sides, and it's completely symmetrical. If we go further down, the animation below shows the same as above, but it's time wish to the South and North. Polls indicated the magnetic field direction is indicated by Blue Lion's. What's current flows indicated by the orange amber arrows. See here, current flying in on the positive side on flowing out on the negative side, and we have self and north on the magnetic flux. Lines are represented by these blue dash lines so we can see the when current flows, it creates a magnetic field, and the magnetic field can be more focused or directed. If we coil the conductor, we go further down. Now we can move on to the next lesson 3. Faraday`s Law Of Electromagnetic Induction: What we're going to look at now is Faraday's law of electromagnetic induction. Now what we have is a magnet represented here by the North and South Poles indicated blue and red. We have a cool and we have a volt meter on. We can measure the voltage as the magnet moves near the coil. We're gonna drive, represent here or try and explain. His wire transformer only operates with alternating current. I will not operate with direct current, so we already know that if current was to flow through the conductor, it would create a magnetic field. However, in the opposite way, we can also prove that by moving a magnet close to the conductor, we can induce current flow. So this is the exact opposite. When current flows through the wind ings, then we will create a magnetic field and when we bring a magnet near the wind ings, we will induce current float. So let's see that in actual we've got a magnet here, and if we move it towards or through the winding, we can induce a voltage in the wind ing's. We can change the direction year we see the direction actually does make a difference to the voltage induced. It's positive or negative, however, notice that when we leave the magnet between the wind ings, no voltages induced because the magnetic field is not changing can see here on the magnetic flux lines that they are static. We refer to those as magnetic or static magnetic flux lines. However, we can induce a voltage when we pivot the magnet, and we can see here that the voltages induced every time the direction of the magnetic field is changed. And we're doing that by rotating the magnet of south South, north, north south. The strength of induced voltage depends upon how close the magnet is to the winding themselves or how close it is to the conductor pivot air. We can see that the induced voltage is quite high, removes a magnet further away. The induced voltage is lower, and in the next lesson, we're going to show you why this is important actually relates to mutual induct. Intense on this is theme main principle of how a transformer works. So let's go to next lesson on. We'll have a look at that now 4. Mutual Induction: mutual induction induction with A C and D. C. All circuits were flowing current. We're having associative magnetic field, but there are subtle differences. Direct current circuit will create a magnetic field that we're not induced. Voltage within. A conductor placed within the field on alternating current circuit has a constantly varying magnetic field on gwil induced voltage within a conductor place within the field. So, as we saw in the previous lesson, it's not being magnetic field itself, which is gonna induce the voltage or the flow of current. It's the changing magnetic field, which is gonna induce the voltage and current. We go down here, we can see the next section on wine. Ning's Transformer Design. The winding refers to a conductor that has been wrapped around a laminate lion core. When alternating current flows through a conductor on expanding and contracting magnetic field will be created if the expanding and contracting magnetic field of One Wind Inc cuts through another nearby winding falsies will be induced in that winding once again, an ultimate and current will create an expanding and contracting magnetic field. But as a d. C current will know, and this means if the expanding and contracting magnetic field of one winding cuts through another nearby winding fault. It will be induced in the nearby winding, be inducing oven Electro Motive Force in a winding by magnetic flux lines generated in another winding is called mutual induction, and it's based upon Faraday's lore of electromagnetic induction. The amount of the MF faulty too, is induced depends on the relative positions off the to wind things. So the amount of voltage that is induced depends upon the position of the wine ings that, as we saw previously, was similar to when we had the magnet on. We brought it close to the wind ings. If we change the direction of the magnetic field and it was very close to the wine ings, then we would induce mawr voltage if we took the magnet further away and change the direction of magnetic field would induce less voltage. And that, essentially, is one of the principles of mutual induction is the strength of induced voltage depends upon how close the change in magnetic field is to the winding or the conductor. So here we can see an example of mutually couple Twinings. If the current is flowing through This is a C current. The magnetic field is gonna expand and contract expanding the tracks expanding contract on as he expands in good tracks across the conductor on the right hand side or the winding on the right, he's going to induce a voltage every time it passes over these wind ing's. 5. Basic Transformer Theory: so in this lesson. Now we're gonna put together all of what we've learned concerning transformer theory. We know that if current flows in a conductor, it creates a magnetic field. But we know in order to induce voltage in another conductor that's nearby, we need to constantly change that magnetic field for the direction of the magnetic field on . In order to do this, we're going to use a C current rather than D C current, which creates only a static magnetic field. Now, using all this information, we can discover how transformer works. Basic Transformer theory Transformer works on the principle that energy can be transferred by magnetic induction from one set of wine ings to another by means of a varying magnetic flux. Magnetic flux is produced by an A C. Source. The winding of the transformer is energized from an A C. Sources called the primary whining on the wining that delivers this ese to load is called the secondary. Winding transformer increases or decreases fault ege, but it does not affect the frequency or power. The image below shows the primary and secondary winding on separate limbs of the magnetic circuit so that we can easily understand how the transformer works. So let's imagine now when we're looking at this site image that the primary current is coming in from the left hand side and it is flowing through. The whining is on the left and then flowing out the secondary winding on the right hand side, which has less wine ings, is in close proximity to the primary, winding. As the current flows through the primary winding, he's gonna create a magnetic field that expands and contracts as this expanding into contracting magnetic field passes over the secondary. Winding is on the right hand side. We are going to induce a voltage in the secondary wind ing's notice. However, there are less wind eggs on the right and on the left, and this means we're going to induce less voltage on the right hand side than we are on the left hand side. When alternating voltage is applied to the primary, winding on alternating current will flow that will magnetize the magnetic core first in one direction on then any other. This alternating flux flowing around the entire limb for the magnetic circuit induces a voltage in both the primary and secondary wind ings since both winding zehr linked by the same flux, the voltage induced per turn of the primary secondary wind ings must be of the same value in same direction. Note that the cause only purpose is to guide and confine magnetic flux. This makes a magnetic flux density higher on the transformer. More efficient transformer core materials are highly permeable. Chill hours, magnetic flux to pass through with a low conductivity, which reduces losses we transform a core is this gray bar represented here. The gray square shape with a hollow piece in the middle on the wine ings wrap around the what we refer to as the limbs off the core. We're going to learn more about that later on, so don't worry. 6. Magnetic Leakage: So a magnetic leakage is coming back to what we noticed earlier when we looked at mutual induction. The further away the conductor is, or the further away. The two conductors are from each other, the less voltage that will be induced due to the changing magnetic field. I think this makes sense. If you have current flowing the flux density or the magnetic field strength, he's gonna be highest at the point where their current is flowing on, its going to gradually reducing strength, the further away you go from the conductor wining. 7. Efficiency: efficiency power is measured in what's efficiency is the ratio of the power output to the power input and can be expressed as efficiency equals power. Output over power input could also be expressed for a transformer as the power of the secondary winding, divided by the power of the primary winding times 100% will give you a sufficiency value. Transformers themselves a very efficient, although, as with everything, there are always some losses. These losses are normally represented by heat, or the less of a loss would be noise or sound. So let's go down and have a look at an example. We've used examples throughout the entire course to ensure that everyone understands the concepts that we're trying to explain. If a machine delivers 10 watts of power and requires 50 watts to operate, efficiency is again power output divided by input. This would be 10. What's divided by 50. What's times that by 100% and that would give us an efficiency off 20% 8. Power and Power Loss: power and power loss. Power is an important concept in electrical engineering and could be used to explain the reasoning for increasing and decreasing voltage power in a transformer could be expressed. His power equals power primary, which equals power secondary, which equals voltage times, current or V times. I notice here in this equation that the power on the primary is exactly the same as the power on the secondary. That means power on the primary winding its the same as power on the secondary winding of a transformer. However, that is an ideal transformer. There will always be some losses. Power loss. The above equation is true, providing there are no losses. But all transformers have copper and core losses. Copper loss is power lost in the primary and secondary wind ings of a transformer due to the O make resistance of the wind, Ing's power loss can be expressed. His power loss It was current squared times resistance or I squared. Ah, well, like was current in our records resistance, copper losses, copper losses can be expressed as hi p squared times r p i s squared times R s. This equation is essentially the same as above. You can see here we had I squared Are our loss equals R squared are for copper losses. We take the high square are and apply it to the primary side on. Then we had that to the secondary side. So we have current primary squared times. Our primary plus current secondary squared times are secondary. So again, the copper losses more or less the same as the power loss. Except we are. I squared. Our primary Plus I square are on the secondary core losses caused by two factors. His two races on eddy current losses. Energy losses by reversing the magnetic field in the core, which occurs when the magnet sizing 80 rises, falls and reverses direction are known as history's. His losses. Any current losses are a result of induce currents circulating in the court in order to be precise. When calculating, transformer efficiency is necessary to incorporate any losses into the efficiency equation . Their efficiency, whose power output divided by power out foot plus a couple Aussies plus core losses times 100%. So again, this is the same as our efficiency equation that we saw earlier, except we've rearranged the equation slightly and this time we will be taking count off losses Summary. We know that power is expressed. His peak was V I. It is therefore logical. They ve increases. I must decrease proportionally. WASPy remains the same. We also know that power losses proportional toe I squared so we can determine that if the voltages doubled, the current will be reduced by a factor off to again. Let me just explain that a little bit more precisely. If we know that p, who's the I? We could go back to the top here concede power equals voltage times current. Then it's logical to assume that if the voltage was to increase in the current with decrease, but the power would remain the same. If the voltage is eight and the current is four and p equals V, I would be eight times for which he calls 32. Now we're not using units here Now imagine we double the but we do not know the value of Oy . We know that pees fixed at 32 of these now 16 because eight times two equals 16. So so for I. So we're trying to find the current we know P, who's the I. We know that P is equal to 32. Know that the is 16 and we're times in it by I So we rearrange the equation we can get I equals 32 divided by 16 which he calls too for power loss. I squared. Our loss equals I squared are so having the circuit current will actually to the power lost being reduced by a factor of four It is therefore beneficial to reduce current in order to reduce losses on this is achieved by increasing the voltage increasing voltage to reduce transmission losses in a grid is primary purpose of a power transformer. So once again, just to go through this power loss, I is squared. So we know that if we can reduce I as much as possible, then our power losses are also gonna be greatly reduced because current is squared. This means that we go, we end up with quite a large number for whatever the value of current is. So We know also that if we ramp up or increase the vault each, then we will reduce the current and if we reduce the current, then we reduce power losses. So all of these equations are related on the reason why we step up voltage to 110,000 volts for to 20 or 3 80 or even higher is because by increasing that voltage, we are reducing the current on reducing our losses. That is one of the primary reasons for increasing the voltage. Another primary reason for increasing the voltage is simply because we require smaller cables for the transmission off electricity, for example, in your car, the starter cable for the engine, from the battery to the starter motor. He's quite thick and quite large in diameter. This is because it has to carry a lot or a large amount of current for a short period of time. You will draw this large current from the battery, and it will turn the engine over. However, we want to increase the voltage significantly and make the current as small as possible. Andi, By having the current as small as possible, this means we can have much, much smaller diameter cables on board. As you can imagine, over a large distribution grid that may stretch hundreds and hundreds of miles, This is a significant cost saving, so that's an additional reason for increasing the voltage is simply because we can reduce the size, diameter off the cables with the transmission cables. 9. Transformer Operation Under No load: transformer operation under no load If the secondary of the transformer he's left open circuited primary current is very low and is referred to as the no load current. No lo current produces a magnetic flocks and supplies. The history sees an eddy current losses in the court. It is also referred to as exciting current. The no low current i E consists of two components. The magnetized. In current, I am on the core. Loss I hate by h is very small in comparison with I am that I am is nearly equal to I E. 10. Turns Ratio: gonna talk about an important concept now for electrical transformers, and that is the turns ratio. In a nutshell. If we can vary the number of turns on a winding or in a secondary winding, and we can also vary the voltage output. Each winding of the transformer contains a certain number of turns. The turns ratio is defined as the ratio of turns in the primary, winding to number of turns in secondary winding turns ratio could be expressed. Using the blow equation turns ratio equals the number of turns on the primary winding divided by the number of turns on the secondary, winding the whining of a transformer is energized from an A Z source is called the primary . Winding on. The wining that delivers this ese to load is called a secondary winding. 11. Voltage ratio: vaulted ratio induced voltage in the transformer is directly proportional to the number of turns on the winding. This is expressed as faulted primary divided by fault, each secondary, which also he calls number of turns on the primary divided by a number of times on the secondary voltage ratio. The ratio of primary voltage to secondary voltage is known as the voltage ratio. The voltage ratio has shown already above is the voltage on the primary winding, divided by the voltage on the secondary, Winding as mentioned previously, the ratio of primary turns of wire to secondary turns of wire is known as the turns ratio. Because the secondary voltage depends upon the number of secondary winding turns exposed to a magnetic flux, it can be deduced that the voltage ratio is equal to the turns ratio. So voltage ratio equals V R and turns ratio equals t R. The R equals T R. The vaulted ratio of 1 to 5 means that for one volt on the primary, there will be five votes on the secondary if the secondary voltage of a transformer is great. In the primary voltage, the transformers, referred to as a step up transformer a ratio of 5 to 1 means that for every five votes in the primary, there will be only one vote on the secondary when secondary voltage is less than primary voltage, transformer is referred to as a step down transformer. So let's have a look on example as discussed, the voltage ratios equal turns ratio. And I think this makes sense. If you have a primary winding and then you have a secondary winding that is within the change in magnetic field associate with the primary winding, then the more wanderings that you have on the secondary will mean that you can induce more voltage in the secondary. And the less warnings that you have on the secondary of was the less one did you have in the magnetic field created by the primary, the less voltage that is going to be induced in the secondary winding seven look an example . The transformer reduces voltage from 120 volts in the primary six volts in the secondary. If the primary has 300 turns on, the secondary, has 15 tons. Find the voltage and turns ratio. Voltage primary. Who's 1 20 faulty secondary who six fault is ratio equals primary. Divided by secondary, she was 120 divided by six, which he was 20 to 1. The voltage ratio is therefore 20 to 1 on the turns ratio. He's also 21 because VR equals t R voltage ratio, he was tells ratio. Have a look. A second example. An iron core transformer with the primary voltage of 240 volts has 250 turns in the primary 50 times in the secondary. Find the secondary voltage. So we've already got the values here for the voltage primary, which is 240. We've got the values for the number of turns on the primary, which is 250 when we got the value for the number of turns on the secondary, which is 50. The voltage on the secondary is not known. However, we can rearrange. The equation has indicated here. Voltage primary divulging by voltage secondary. He hauls number of terms in the primary, divided by number of terms on secondary on the move solved the equation for the S off voltage on the secondary. So limp put the values N S a n p times V p equals 50/2 50 times to 40 and this equals 48 volts. So the voltage on the secondary is 48 faults, and we've managed to solve this equation simply by knowing that the voltage ratio is equal to the turns ratio on then plugging in the values. So an important concept, voltage ratio and turns ratio the to ah linked with each other on this makes sense. This a number of turns exposed to a magnetic field will number of turns exposed to the change in magnetic field does dictate the amount of voltage that is induced in the secondary winding. 12. Step-Up And Step-Down Transformers: step up and step down transformers. Now that we know about turns ratio in voltage ratio, we can look at step up and step down Transformers. Step up transformer increases the primary voltage to, ah, higher secondary voltage, for example, from 10-K B to 110 K V. A step up transformer is used by power stations to increase the voltage and reduce the amps . This reduction in amps allows a much smaller cable to be used for distribution, which is a huge benefit when distributing into a grid that could stretch several 100 miles . Typical voltage ranges in the national grid may be anything from 135 K V 2 765 k V, and here we can see a step up transformer. We can see the primary winding is on the left. The corps is indicated in blue on the secondary warnings on the right secondary warnings There are simply more off them, and that means that more winding zehr exposed to the varying magnetic field created by the primary winding. This results in having a step up transformer because mawr voltages induced in the secondary winding than there is voltage in the primary winding and that is a step up transformer. Step down. The transformer reduces the primary voltage to a low voltage, for example, from 110 K V 2 10 K V. The step down transformers used to reduce voltage to safer levels prior to it being distributed to industrial and residential areas. Typical voltages for industrial areas, maybe 69 k V 26 Gavey, 20 k V 10-K V six K V and even free KV. Both residential areas operate with a final voltage of 380 volts to 20 volts 110 volts. The exact voltage range depends upon the geographic location Can see here a step down transformer again the core is indicated in blue on this time there are less wind ings on the secondary than there are on the primary on. This means that it is a step down transformer. There are less warnings on the secondary, which means there is less voltage induced on the secondary and therefore it is a step down transformer and finally we have a step, nothing which does not really exist. The transformer does not change the voltage primary and secondary voltage juice are the same. Now we can see here the primary winding is on the left hand side. There are the exact same number of wine dings on the left, as there are on the right on. This means that the induced voltage in the secondary winding is gonna be the same as the voltage on the primary winding. I know, he said that step nothing. Transformers do not actually exist, but this isn't 100% true. Where we need to clean up electrical signals, we will use a step. Nothing transformer on. The reason is the voltage from the primary to the secondary. He's transferred, you could say, whereas the noise in the electrical signal is no. So sometimes you'll find transformers are used for cleaning up electrical signals where you only want the voltage to be induced in the secondary and nothing else. 13. The Grid: Let's have a look now at the layout of a typical national grid. So I had the great The blow image shows a tipple grid starting from generation in red to transmission. Distribution of finally the end consumer indicated in black? No, the divorce Jesus shown in ranges because the grid voltage varies depending upon country. Sometimes they're the same as with neighboring countries and sometimes not. So we can see on the left hand side. We've got here a power station also known as a generating station. It's going to distribute electricity to a generator. Step up transformer. From there, we're gonna send it to transmission lines. On the voltage is gonna be a lot higher. So we're gonna This is a generator step up transformer. So let's imagine it's stepping up from 20 k v up to 138 k V. It's gonna be transmitted. Then there will be some consumers here transmitting customer, but most consumers are going to be more towards the right hand side. But before we can get to our end, consumers have to reduce the volte again, using a substation step down, transformer on. We're going to reduce it from for example, 138 K V back down to 20 K V or 26 K v. I mean, at this point, we will start to have some of our consumers notice that the distribution level consumers are taking the voltage at different voltage ranges for heavy industrial plants. You will find that they get voltage delivered at, for example, 26 K V on then at lower or not so heavy industrialized plants will find they consume electricity at, for example, 13 or 10-K V. And finally, wherever and consumer on day will received their voltage a relatively low voltage, perhaps even 380 volts. So the three areas are red generation. Step up the voltage to transmission, which is in blue on. Then we're going to reduce the voltage again to get it to the distribution level in green on their name consumers, which are indicated in black and that is essentially national grid. Now, remember, as we spoke about earlier, the reason we step up the voltage in the first place is one so we can reduce our losses during transmission on to increasing the voltage means that we can have smaller diameter cables, which is a huge cost saving when the transmission lines stretch over hundreds and hundreds of miles. So that's a brief overview of a great or national greet and how it works. 14. Transformer Designs: transformer designs. There are many different types of transformer in service today, but this course will cover the three main types that are very common. Transformers could be roughly split into two main groups. Liquid immersed, the transformer core and winding zehr placed within a tank and immersed within insulating liquid. She's usually mineral oil and dry. The transformer has no tank and his air cooled. But the purposes of this course we will discuss the three most common transformer designs. Conservative transformer tank is connected to an expansion tank, conservative types of used for high cable ratings. Hermetic, the transformer tank is hermetically sealed. No connection to atmosphere, hermetic types of generally used for smaller K, the applications and Troy used for low medium Kaveh applications. Dr. Transformers are also used when he most transformers represent to greater fire risk due to the mineral off, the mineral or itself increases the fire load. So let's do a quick recap. We got two main groups. These are liquid immersed. Andi dry on In these two groups, we've got three different designs of transformer. We've got the conservative. That's this transformer here it is called a conservative type transformer because this tank in the back where my mouse is now is a conservative tank. If we go down, we can see here a hermetic transformer and further down we have a dry type transformer. The dry type transformer is the only one that does not sit within the tank and is no immersed in insulating liquid. Go to the top again. You can see here. The tank full of insulating liquid, which houses all the main transformer components on this is for large applications, again is a conservative type hermetic. Again, we have a tank on the main components, such as the Koran. Twinings sit within the tank. This transformer is used for low to medium K via applications, and finally, the dry type transformer, which does not sit within a tank. He's only surrounded by hair, and this is used for low and medium cavey A applications as well. So those are the three main designs in the two groups. Classes liquid immersed and dry. If you would click on any of these images or the text underneath the image, you would also load unassociated Freedy model, which we're gonna talk about later on. In the course on these interactive three D models, we're gonna be using a lot throughout the course 15. Dry Type Transformer: So here we have a dry type electrical transformer on the bottom of the transformer. This gray area here, these are fans, and they will be used to blow air across the transformer to cool. It can see we've got wheels on the bottom for moving the transformer into position. Andi, if we go further up, we can see the top of the transformer frame. Assuming here on the talking to France, former afraid as thes connections coming out of the top 12 free on these will connect to electrical terminals When looking at, terminals always pay attention to the size off the connections where they are short and fat . This indicates that there is a higher level of current, and they lower voltage where the connections are thinner and longer. This indicates that there is a higher voltage on a lower current. Just expand the transformer out into its various components. Conceived this blue area here, the blue area is the transformer core is a laminate. Steel sheets that I helped together normally with cables or sometimes with some form of adhesive on the sheets will lie on top of each other, will be clamped together. The lower part of the transformer core is called the yolk. On these three vertical pieces that attached to yoke are called the transformer limbs. In the middle, whether or no limbs is or for two is transformer call windows. The additional Yoki could be seeing here top that is a transformer core yoke, and we can see that which is clamp onto our lower limbs. We turn around here, we can see the clamps. These steel circular clamps will hold the transformer core together and keep it under compression. In addition to that, we have the low voltage Twinings he's here on. The high voltage winding is contained within this red area here now the low voltage Twinings and the high voltage wind ings. The low voltage linings will always be closest to the core, and the high voltage linings will be further away from the core. The reason for this is simply due to heat. We want to be able to get rid of that he as quickly as possible. The heat created by transformer is often one of the design limiting factors. So by putting a high voltage linings on the outside or Furbish from the core, we can remove some of this heat a lot more efficiently on if we put the high voltage wind ings next to the court in the live voltage wind ings further house. So it's purely a decision based upon heat. And now we can get rid of that heat eyes, a dry type transformer. We can assemble again and that is how you're gonna see it typically installed in next few videos, we're gonna look a conservative type transformer on also a hermetic type transformer. 16. Hermetic Transformer: Freedy hermetic liquid emerges transformer Click on a blow imaged Lodin Interactive three D medical transformer model So we can see now that the hermetic or transformer Or I should say the hermetic liquid insulated transformer model has loaded sometimes referred to this transformers and oil insulate transformer. That is simply because 95% off insulated transformers are filled with oil or mineral oil. Let's just do a little spin and we can have a look around and see again. There are some clues here about which side is the high voltage side on which side is the low voltage side and we can determine that by looking at bushings. The bushings are these pointy, sticky out bits that come out of the transformer tank. The low voltage pushing zehr gonna be varies with the thick, large connections such as these ones. Here is four off them, one of them being the neutral Onda. We can see the higher voltage bushings on the opposite side. They look like they're mawr insulated. The bushings have this special shield against tracking and also against weather. Andi conceive. There also high voltage because it would not be able to carry a large amount of current compared the opposite side because the connections are much thinner. So that's indicating that the voltage attire and the current is lower on on this side, we can see that the current would be higher in the voltage lower. Where else can we see? Could see the main tank has thes rips or things on the side. These are for exchanging heat. When the transformer is hot, the heat will be conducted into these spins on air will take the heat away. Just expand the model fully enclosing conceal was on the bottom. We got these rails. These are for moving the transformer into its final resting position. We have a device on the top here, which looks to be a temperature gauge that may also be some sort of gas actress related mounted to the top of the tank, although usually this will be in the middle, and that is for detecting any electrical faults within the transformer, which may create bubbles off gas. We consider this temperature monitor and as a terminal connection on the bottom that is the exterior off the medic transformer. We can also see some lifting eye bolts in the corners is one these other four of those four lifting a transformer using a crane or a winch on, Obviously the feeling pipe, which is the point we're staring at. Now we expand the l. Was that a top? We've got some nuts and bolts without the bushings. Without the transformer tank lead, we got the connections to the lower part, the bushings underneath. We can go further down here. Consider the top of the transformer core, which is referred to as a transformer yoke on the laminate. Still sheets that are pressed together that form the core. Consider low voltage warnings here, wrapped around the inside. These are closest to the court. The high voltage warnings are further away from the core. The reason for this is that the high voltage linings create more heat. In order to get rid of that heat, we will make some further away from the core, and that means more into late liquid were coming to contact with the high voltage linings, and that heat will be removed more quickly, go further down. We can see that the court has free limbs because, let's say, free face, electrical transformer, one limb to and free and again. These limbs are made of lemon. It's still sheets are insulated from each other. Insulating the sheets from each other reduces recall eddy currents on. This reduces our losses and makes the transformer more efficient. We go further down. We can see the bottom of the core, which is the transformer yoke again on all of these BC's slot together on will be held in place by adhesive, or sometimes they'll be held together using steel cable joints. We could see the connections represented here. We can see the low voltage connection coming out connecting on the bottom. Another one on the high voltage connections are connecting here, coming out, connecting to the bottom there, and that will go to the Patri bushing. Nice, essentially the construction off a frenetic type transformer. There we conceive or assembled again. Typically, it's unlikely you're going to see the interior off a medic like transformer. The interior does not look as it's displayed here on the model. It is like to see a more realistic internal model of a transformer than I see. Just check out the transformer conservative freely model. However, for representative purposes, this is a very good model, and it's a lot more easy to see how the transformers constructed 17. Conservator Transformer: a case. And now let's have a look at our third and final type off. Electrical transformer on that transformer is the conservative type. We'll do a quick spin. Okay, so this is our electrical conservative type Transformer on rather than go for each of the individual pc's like we did in the last couple of transformers. What I'm gonna do is just show you some of the differences between this transformer on the other two. So we've got here a control box. This control box is for a tap changer. Andi, With this tap changer control box, you'll be able to see the number of taps you tap changer has made since it's been installed or since a specific point in time. We're gonna talk about tap change a bit later on side on a stress on that, too. Long of the moment we've got here a temperature control box and also a temperature indication gauge on. We've got separate video on this against I'm not gonna stay too long on this topic, but essentially this box is used for monitory. The insulation liquid temperature on the red indicator will be used as an alarm on the black is the actual temperature indication off the insulating liquid. This black needle here, as I say, we've got a separate 10 minute video on this side. Honor spent too long on it. You can see here or the set points. Those are four alarms, cut outs and for starting and stopping cooling fans and pumps etcetera on the side of the transform we've got. Cooling radiators on the insulating liquid will flow through the radiators on some of that heat will be taken away by the air. The tank itself is quite large because he's got a house, the entire transformer core Onda with wind ing's sometimes that most times they will actually ship the transformer empty and under a slight vacuum. They will ship the transform an empty, and they'll put a slight pressure on the tank on. The reason they put the pressure on the tank is so that when it arrives at its destination , the pressure within the tank should be roughly the same where it should actually be exactly the same. If the pressure has changed, then we know we've got a leak on. That means that some of the ambient air has gone into the tank which is what we don't want on. If that's occurred, we need to put the transformer under vacuum again in order to get the ambient air out. I'm being air contains moisture and other foreign bodies, which we don't want in our transformer before we fill it up with insulating liquid. The other differences. Here we can see a tap changer here. It would be mounted within the transformer tank. We've also got a Buchholz relay. Got a separate video for that as well. The book over three layers of protection device used on the transformer. We can see it's mounted between on outlet fly Fear. Coming out of the tank through the book holds relay and then into the conservative tank into the base of the tank has been around here. Maybe we can see it. We can see there is going into the base off you conservative tank because the tank is just an expansion vessel. It's his round cylindrical item here. Onda. We use that for allowing the insulating liquid to expand and contract due to temperature variation. We go down, we can see a silica gel for either. That's uses a dehydrator to extract moisture from the incoming here, and we've also got a oil cup, which is used for extracting or for sticking foreign bodies. So, in other words, when we're drawing air into the conservative tank, we will remove some of the former and bodies within the air, such as dust. We've also got four cooling fans. A cooling fans will start when the transformer is heavily loaded that we can actually start now. We go because, um, that is essentially a conservative type transformer. As I say, we've got an individual video for the temperature control and monitoring for the Bushings book, All three late conservative breather and also transformer cooling. So I don't spend too long in this model. I think most of the concept was covered already and the other two videos on actually progressively the course. You're gonna look on each of these individual components in more detail. So without further delay, let's go into next lesson. 18. Transformer Cooling: in this lesson, we're gonna look at transformer cooling specifically for insulated liquid type transformers . They were conceived. This type of transformer has radiators mounted onto both sides of the tank. On. The idea with these radiators is that we can have what liquid that flows into the top of the radiators on will be cooled down, drop down to the lower part of the radiators on will, then reenter the tank on due to natural conviction. We will draw more all in at the top, and it will sink back down as it's called, and this process will continue as it set up. At the moment, the fans are not turning. We consider each radio bankers one to fans, So in total, there are four fans on. None of these are turning. So if we're gonna class this by its cooling method, which is how many transformers are classed, then we would say it's a oil natural 40 N. Because it's circulating naturally, air natural because the air is passing over the radiators. Naturally, when we say naturally, I'm referring you to natural confection. So if the insulating medium or insulate liquid was flowing out of the top here into the radiators. It would be cool by the air. The cool air would be coming in. The bottom cooler, regretted to get warmer, would rise up to the top. And as it passes over the radiators, traveling vertically upwards, it will cool the insulation liquid. And that will cause inflation liquid to drop downwards. Because now it's less dense on, then will flow back into the tank so that his air natural oil natural once again, I have to stress that they call it oil natural. But no. All transformers use mineral oil has, um, insulating medium, or about 95% of them do so you will see the abbreviations of the acronyms for O N a N. And that means oil natural air natural. However, if we were to turn the fans on now, we have a different cooling set up. This is now oil natural air forced. So now that we've seen a transformer cooling type in action were actually two types. Let's discuss, we'll explain how the cooling acronyms work. Transformer cooling acronyms explained transformer name place. Use acronyms to classify the transformer cooling type to such examples are off off. Andi Onan, each letter of the acronym is associated with a specific meaning or word. So the first letter is the internal cooling medium in contact with the wind ing's So, for example, refers to mineral oil or synthetic insulating liquid with a fire point below 300 degrees Celsius. Okay, his name's late in liquid with fire point above 300 degrees Celsius on l business late in liquid with no measurable fire point has a little is used for 95% transformers. We will often see the oh indicating mineral oil. The second letter is for the circulation mechanism for internal cooling 1,000,000. What that essentially means is, what are we using to cool the insulating liquid down so we can use natural conviction? She's this area here. Natural convection flow through cooling equipment on why Ning's forced circulation for a cooling equipment as the heat exchanger in the cooling pumps and natural conviction flow in wind ings that it's a symbol four F on D four circulation for a cooling equipment on flow directed into the main wind ing's. The third letter in the acronym is for the external cooling medium. Hes for air on W is for water the fourth letter circulation mechanism for external cooling medium, which will be end for natural conviction, or F for forced circulation fans and pumps. So putting this all together, let's just imagine for a moment that we had a transformer on did it was circulating oil naturally or due to natural conviction, so a symbol that we reduced where two singles to letter Sorry would be Oh, on in now, third letter is what we're using for cooling Andi. Normally, this will always be hair on how recirculating the air we can say. Is that natural conviction or is it forced on? We'll use fans or pumps, so let's have a look at some other examples. So he is one such example. We can see our transformer core is in the middle of the image here on our findings are indicated on the outside, on what we've got to circulation pumps to these two blue areas here on, they are circulating fluid into the radiators or circulating food around the transformer. We've also got to fans. She's one on the right hand side and one on the left. Consider the direction of the oldest coming in the top on then down on that's being forced through the pump. The oil will normally flow to the top first. This is simply because it will be warm or hot, and it makes more sense for the hot oil to pass through the top first and be called down. Then it would have rear pumping in the other direction, which is against the general rule for natural conviction. Member of it cools down, is less dense and will naturally fall down anyway. So this set up is called O F. A F offer. Onda o F A f means oil, which is our insulating medium forced, which means it's forced around the transformer tanker into radiators on air, which is a cooling medium. Andi forced, which means the air is being forced across the radiators, so oil forced air force tore off as it is wrote upon the transformer nameplate. Here's another example. This one is called Oh swf Oil force Water forced. Now the old again is being forced from the top for a pump on that being forced down across a heat exchange of this time on back into the transformer. Now the reason It's a heat exchanger on, not radiator is because we're using water to conceive your let's be enforced. That's the same as the last image, but the water is also be enforced. This is unusual because we're using water instead of air. But there's a good reason why we using water instead of air. Well, there's good reason why we would do that now. One of the reasons is that water has a much higher cooling capacity than air due to tyre density. But the other reason is that handy in air may not be readily available. For example, on underground mining installation that has transformers installed, they will not use ambient air for cooling. The reason is they need to get the ambient air down into the mine from the surface, and this is quite difficult because the mind maybe hundreds and hundreds of meters underground. Not only that, they would need a relatively large volume of air for cooling on. This large volume of air has to come for a large duct, which is also in practical cause. Ducks take up a lot of space and if they take up a lot of space, that means in mining they have to dig wider chefs and that carries additional costs. So instead of using air, there were select water, which is a lot easier to pump down into. The mine on is also perhaps more readily available because he's pumped down into the mine to the transformer. It is a forced system or water forced. The downside with this is that if water comes into contact with the insulating liquid or with the oil, it will contaminate the oil on. This could have potentially catastrophic effects now, in order to combat this but reduce the likelihood of this occurring. The type of the exchange employed for the system will be a shell and tube type heat exchanger on the shelling tube type he'd exchangeable have what they refer to his double walls on. What will happen is if there is a leak inside the heat exchange up the water will leak out of the first pipe and going to a secondary pipe. Now the secondary pipe is just larger diameter and axes a sheath across the main interior pipe. But when water leaks out into this outer, she thought out a pipe. It will activate a leak alarm. Now, at this point when the alarm is activated, the engineers will know. Okay, we have a leak on a heat exchanger. But as long as the water does not get past the second out a war or the larger diamonds pipe , then they will not have any problems. So there are pros and cons to using water as a coolie medium, normally almost always air is favored. But the reasons for water have been explained on it may be that water is sometimes the only and the best option. There are also other problems associate refusing water to cool the transformer, one of them being that the parts can corrode. This especially to review using sea water, is a cooling medium. On the final problem being simply, the water can freeze. A fresh water source may freeze in winter. On this could damage the heat exchanger or caused the pipes to rupture as well is that the freezing itself takes away the cooling power off the water because the water is no longer flowing, so the transformer may rapidly overheat. So all of this has to be taken into consideration when deciding to use a water forced cooling method can see here. This is oil, natural air natural. The oil is circulating naturally, Jews conviction and so's here. There are no pumps and there are no fans. Another example, he would be oil. Natural air forced the oily circle. A. Naturally, there are no pumps on and we have air forced where the air convey forced across the radiators if required, motors, air said, if required, because generally you will have a system which is oil, natural air natural, and the transformer will be designed so that the fans are not required to be in service along the time. So essentially, what will happen is the transformer will be lightly loaded. Perhaps Andi Oil, Natural Air Natural, is sufficient to call the transformer down. If the transformer becomes more heavily loaded, it will become warmer. The temperature will increase Andi. Then the fans were cut in to remove this excess heat or waste heat as quickly as possible. And again, if we go back to our example here, we can see this is a oil natural hair, natural transformer. But if I click the play button, then it's an oil natural air forced type transformer on the item. Controlling the start and stop of any pumps or fans would be this. The moment of books here 19. Transformer Core: So now we're looking at a transformer core, his transformer cores taken from a liquid immersed transformer, specifically a conservative type transformer. But generally designs are much the same for all transformer cause the core itself consists of free limbs. This is indicating that the transformer is a free phase Transformer. The limbs are on the left, center on right. Connecting the limbs together is the yolk. We conceive the yoga, the top here and also at the bottom so the limbs will attach into the yolk on the yolk itself will be held together using steel straps. 123 On On the other side, we can see the steel straps again. Typically, the large transformers are held together using steel straps over the smaller transformers. We'll use a inorganic adhesive on that will hold the transformer Cool together when I say transformer call. What I actually mean are the laminated steel plates. Steel consists of carbon and iron. On it is the iron that is the magnetic part of the construction. Now, in order to reduce any losses, we will take thin laminate steel sheets. The thin lemonade sheets are cold rolled. Typically there we under 0.3 millimeter thick. They'll then be insulated from one another. Using and inorganic material on all of these laminate sheets will be joined at one point to Earth, which makes it easier to recognize if the court has been grounded mistakenly, so they will be connected to Earth. A singular point. The reason for cold rolling these thin sheets is simply to align the magnetic grain within the steel itself. On this increases efficiency. If we were to have just a block of iron, which is in the past, how transformers were constructed there would utilize a block of iron with the wine is wrapped around the iron. The losses associate ID with the transformer would be far higher. Transformer core is designed to focus the magnetic flux lines from the primary winding onto the secondary. Winding on this increases efficiency. If the magnetic flux lines are not focused than they are going in, directions that are unintended on this means they will not induced voltage into the secondary winding. So for this reason, it's important to focus the magnetic flux lines as much as possible. And that is the reason for designing the core and its shape the way it is on notice. Finally, the bottom and top of the core. We have some still construction. This is used for mounting the core to the base of the tank, so that is completely stable on remains in the correct position as it was designed on the top of the transformer. Core can also be mounted to the lid off the transformer, if necessary, on the little resealed onto the tank using a gasket. 20. Transformer Windings: whining. Zehr installed concentric Klay around the core limbs. The inner shell designates the layer of whining is closest to the call. There is in a mid shell on Dora now to shell, depending upon if regulating winding his prison, Low voltage twinings are always install closest to the core. High voltage wining zehr always install furthest from the core, each winding as approximately the same height around the limb. Dis reduces losses and lowers the potential short circuit stresses. When we talk about a regulating winding, we're talking about a winding that is attached to a tap changer. So we are regulating the output voltage of the transformer, and that's why it's called a regulatory wanding or regulating warning Z. The wine is here. These would be the hatred rewinding because he's on the outside whining czar constructed off aluminium or copper, depending upon the availability of materials and cost copper. Winding transformers require wind ings with smaller dimensions compared to their counterparts aluminium, winding transformers. We're human here that the nameplate ratings of the same copper conductivity is about 40% hardened. Aluminium aluminium weighs only about 30% off the way of copper. A compromise between the two materials can be made, especially if the decision is based not just upon conductivity and wait, but also on costs. With aluminium being cheaper. Warnings a usually cold road during fabrication. This gives the warnings are higher mechanical strength on higher resistance to deformation during short circuit conditions. In addition to coal rolling, whining, zehr sometimes and kneeled prior to the insulating material being applied, each strand is smooth on without sharp corners. This reduces die electric losses. Each conductor consists of strands. It is these rectangular shape strands, a used in parallel to form. The part referred to as a conductor, paralleled conductors, then form linings. The rectangular shape of the strands is used in order to use lies space within the window effectively. It is not uncommon to use circular strands for smaller transformers, but even then, the sides are often roll flat in order to utilize the space more effectively. The main consideration for larger transformers is quite often not the thermal already kind losses that is the winding its ability to withstand short circuit forces. I eat the wine ings, mechanical strength. Note. The ampere rating of the transformer can be increased by increasing the thickness of the primary and secondary Twinings. Whilst the voltage rating can be increased by increasing the voltage rating off the wine ings insulation we could see year winding is mounted on a transformer core. That is how you would see it in real life. Squatter. Realistic three D model. If you got a couple, do a quick re tough we can see that whining Zehr, constructed of aluminium or copper like copper, is mawr conductive than aluminium. But copper is also heavier on its more expensive, so there's always a compromise. If space is a consideration or is a primary concern, then you probably gonna go for copper because it is more conductive and requires less volume space for volumetric space. Compared to aluminium. However, like I say, aluminium is whiter and cheaper, so it really does depend on how you're going to use a transformer, what's its application and where it's going to be installed. Cold rolling gives the warnings of high mechanical strength. This is true, and it also helps to align the magnetic rain within the winding, which will increase the overall efficiency off the transformer, the one who themselves are usually rectangular in space. This is just to save space because if they rectangular in shape, we can actually put more wind ings into the transformer whilst requiring less space. This is not true if the wining czar circular in shape, thermal and eddy current losses are obviously concern. But what most people forget is that there is also a stress based upon the winding is your in short circuit and this is actually a mechanical stress. It is possible for the wildlings and the insulation doing into rupture following a large short circuit. So the warnings, also after be mechanically strong. And the final common here is simply that if we increase the overall thickness with warnings , then we can carry more camps on the whining. And if we increase the level of insulation than we can carry more volts, if you think about it, this actually makes sense. If we look a low voltage pushing, we know sis that the bushing as less insulation on the outside on is very thick because we can carry more amps, and if we look at high voltage, pushing will notice it has mawr insulation. The bushing is better insulated, especially if we consider creepy and tracking But the overall conductor itself is actually thinner because the voltage has been increased on the current has been reduced. Today's transformer wind ings was actually lucky enough to visit a transformer manufacturing plant in France. Once Andi, I saw one of the transformers being made on. I saw the paper insulation being applied to the wind ings on. I have to say I was very surprised because they were applying the paper insulation my hand . Somebody was actually there and they were wrapping every single one of these rectangular conductors and they got a wining and they were doing it her hand with very thin paper. Now, obviously, if you're doing this per hand, then you have to be especially diligent because one simple failure will lead to a failure off the transformer. And for this reason, I was very, very surprised that they were doing it by hand when I thought it would make much more sense for a robot's or perhaps a machine to do the task. But apparently they've done it by hand for a very long time. The fairy rate was very local, is very low, and that's gonna be the way they continue to do it. Let's move on with the next lesson 21. Dehydrating Breather: today we're gonna look at silica gel Breathers on these were installed on the electrical transformers. I'm gonna explain to you what it is and how it works. Now. Silica gel breeders are also referred to his dehydrating, grievous or dehydrator breathers. And if we have a look, we can see one amounted to the transformer. This section here now we can see it's connected to what they call a conservative tank. Next on the took on what it's actually doing is allowing the transformer to breathe. That means it's allowing air to pass in and out of the conservative tank. So quick transformer recap For those who don't know, this is a conservative tank this large cylindrical tank mounted above the main tank. The main tank is this tank here, where all the pointy stick er pits are so the main tank is there now to transform itself is full of an insulating liquid. This is almost always mineral oil 95% of the time, and as the transformer gets hot, it will caused the insulating liquid to expand on. As the transformer cools, insulating liquid will again contract, so it has his constant expanding and contracting motion Now, the domo liquid level in the transformer would be around this line here. So imagined imaginary line connecting these two bolts on the conservative tank on. That would be the normal oil level line with the normal insulating liquid line on. As a transformer temperature increases, the insulating liquid will expand on. It will cause the inside liquid to actually rise up. So as it's expanding, it is traveling upwards. And as it contracts, the liquid is moving further down into the tank, now above or inside to conserve to tank, as we can see here, if you can imagine, the tank is half full. As it expands, the air above the liquid has to go somewhere. Otherwise, you could end up building a positive pressure inside the tank. Now, we don't want this, so we allow the air to vent to atmosphere. And we do this by putting a small pipe in the top, which we can just about see here, there Andi able pass out of that small pipe. You're one of the pipe outs we can see connects to the top of the conservative tank, and then it goes down here and connects Teoh breather. So it connects to the breather. As you can imagine, when the temperature increases, yeah gets pushed out and it will pass through the breather and outwards. And then when it cools down, the air will be drawn back in, and it prevents a positive or negative pressure building up inside the transformer tank were inside the conservative tankers. Well, let's just show you even animation how he breathing in and out works for what is occurring when the transformer breeze, you know now. So as we could see on the animation here, transformer temperature increases the liquid level increases or the liquid expands on. It pushes the air out of the conservative tank down here and out for a breather. Now in the opposite direction. We can see now that transformer temperatures cooling down on the liquid contracts as it contracts it is drawing ambient air in through the breather and into the conservative tank . So what's the breather Actually doing well, the air is gonna be drawn in through the bottom or passes through holes in the bottom of the casing. We can see he's small lines here. The small dots, these dots on the right hand side of the screen allow the air to pass in and out off the breeder on the bottom, we have what's called an oil trap. The oil trap prevents foreign particles from entering into the conservative, coming into contact with the insulating liquid so bits of dust or any other foreign bodies will actually get stuck to the oil on. They will not be allowed to pass in to the breather, so it keeps particles of dust out and keep that insulating liquid cream. If we gol higher up here, then once he's passed the era, come down here and then passed up through the center off the breather on it will go up, up, up. Andi will then come into he silica gel area. Now I'm one of the silica gel. There are other drying agents that use, but silica gel is the most readily available and the most common. Not a silica gel absorbs as much water from the air as possible, and it prevents moisture entering into he conservative tank area and coming into contact with our insulating liquid. As it absorbs moisture, you will actually change color starting from the bottom, working its way up. This is very important because it makes it much easier to know when to change the silica Joe. Once you get to the top area, once the whole container is saturated, except maybe the top 25% it is then definitely time to change the silica gel. And to do that, we go for a process called regeneration. On essential you need to do is take the silica gel out of its container, heated up in another, nor a suitably hot surface or a suitably hot area on. The moisture will be released from the silica gel at a certain temperature. On we will have regenerated are silica gel, and we can then use again to absorb moisture. Now the silica gel that's used in here is very similar to the silica gel you'll find in a new pair of trainers or a new pair of shoes. It's those little packets that you get on. Often people open them and I'll find him in their shoes or their trainers and think, What of these four? Well, it's actually for absorbing moisture, and that's what there's little package is. A four typically silica gel will absorb one killer ground of moisture for every five kilograms of silica gel, so about 20% by volume is the amount that silica gel can absorb, which is a lot. So now the air has been could say, filtered or cleaned of foreign particles. The foreign particles have been separated by a oil trapped at the bottom, as we saw here. And then it passes through the silica gel where the air will be dried and now finally will be allowed to pass up to the conservative tank. And we did all this because we don't want our insulating liquid to come into contact with moisture on dirt. If we do, that will devalue the properties off the insulating liquid. We will degrade them, and this could lead to the formation off sludge or a lower die electric strip off the insulating liquid, which is that this is something that we don't want, and that is the reason why we have the breathe in the first place. Let's have a look now at the breather in action, so here's an example of a silica gel breather. As we can see, the silica gel is becoming saturated from the bottom, heading up towards the top. We concedes more pink on the bottom, on purple on the top. At about this point where we are now, we would say it's time to change the silica gel in the river. Ideally, you should be doing it before it gets the last 20 or 25%. That is not saturated. The lady leave it. The higher the probability that you'll get some moisture carry over into the conservative off the transformer. Let's have a look at another example. As we can see here, the moisture again is building up from the bottom to the top. The bottom is clear. On the top is orange. This color coding system used for breathers is very handy allows you to quickly establish if you need to change the breathers or not. If you are changing, the grief is quite frequently. Where you can actually do is install a longer cylinder of silica gel. Typically IMAP silica gel. The size of the bria is dictated by the manufacturer on this will be dependent upon the amount of insulating liquid within the transformer. Obviously, a transformer that has 30 cubic meters of insulating liquid. He's going to need a larger breather than one that only has five cubic meters of insulating liquid because the sheer volume of air passing in and out of the transformer is going to be larger. 22. Oil Level Indication: this magnetic oil gauge, which we can seize mounted onto the side of a tank, is used to measure the liquid level within the tank resume. Now, this is actually a conservative type tank fitted to an electrical transformer to see its long and cylindrical in shape on the magnetic allure gauge is mounted on to the end. The magnetic or gauge has a float. I'll just go inside so we can have a look on. The float is attached to a float arm, so there is the float. There is a float arm on. This will actually connect to a dial gauge just this one here. And as the float moves up and down, it's actually going to give us a level indication on the outside here, the red lines at the bottom of the gauge thes signify alarm set points or perhaps trip points on these will be relayed back to a control room or a manned area and see also the junction box where we connect cables on another cable connection. Here, we can see that there is a me in on a max indication on. We can also see what the level should be at approximately 20 degrees Celsius. So let's see the gauge in action. That guy's there. Imagine the liquid level is increasing until it reaches Max. And as you saw there, the float has now moved up to the top. Off the tank can see that the flow is synchronized with the dial gauge so that the position that float is directly proportional to the level that indicates. And now we can see the float coming back down again. And that is our magnetic oil gauge on a transformer works. The gauge itself is actually coupled from the inside to the outside Vier a magnet. The magnet itself is what they term. A driver and a follower. The driver magnetic. We'll pivot along with the float on as it pivots. It will also rotate the follower magnet on the following. Magnetic will be connected on a rod to this needle on the dog age, and that will make the needle turn and give us a reading on the dial. Gauge a relatively simple piece of instrumentation. Sometimes you'll see these magnetic or gauges or MOCs as they're called. We have a bevel gear. This is just additional component in the drive train between the floats on the needle. But the essential concept is that as the float moves, a proportional response should be given on the dog age on. This should indicate its level. So let's have a look. Now, using a two D animation we can see here is the level in the tank increases. The float will be carried up Andi as the level decreases. That float will be carried down on Indication will change in proportion to where the float is. There are other types off magnetic oil gauge. This is a different type. As we can see, the tank level is increasing and decreasing on. What we'll have is a float, which is a magnetic float. And as this travels up through the channel here, the magnet will rotate a red dial on def. It indicates bread. Then that will indicate where the level is. As it traveled back down again. It will flip these red dials back to the black position Andi. That will then indicate that the magnet has travelled downwards or the level has decreased , so it's a different type of magnetic oil gauge. The most important thing to realize with magnetic or gauges is that They are very useful when you're taking a direct measurement, but you do not wish to mix two systems. For example, the mock, as he's here, is completely contained within the system on the gauge, which is mounted on the outside, does not come into contact with the liquid contained within the system. We can also see this on our other example. As we can see here, the gauge is not connected to the interior. It is actually coupled viral magnet to the interior on. This means that the interior and exterior are completely separate. This reduces the risk of leak each through things such as gasket or O rings, which we may require for sealing. It also makes maintenance of the exterior components a lot easier. 23. Temperature Indication: transformer temperature monitoring. He's conducted either directly or indirectly. Typically, there are two modes of measurement. One is referred to as hot spot measurement, and the second is referred to as top oil measurement. The example we can see in front of us is a typical thermometer with a temperature control box used for a liquid insulated conservative type transformer. We can see the temperature monitor or the thermometer here. This is the section that would be screwed into top of the transformer tank. See the cable, then comes down and connects onto a monitoring and control box. The box has a dog age, which indicates the temperature of the transformer. That's this black needle here on the Red Needle indicates the alarm set point. If the black needle should surpass this red needle, it will activate an alarm. The alarm in his case has been set at approximately 100 degrees Celsius, although the temperature set point will vary depending on your transformer. The SEC point is almost always configured by the manufacturer, although it's also possible to adjust a set point on site. For go down, we can see four other dials with red arrows. These red arrows indicate set points thes, maybe alarms or trips. They may also be to start and stop pumps or to start and stop cooling fans. So not only are we measuring the temperature were also able to control the temperature by using these cuttings and cut outs. Additionally, it's possible to activate an alarm or a shutdown if needed. Let's now take a look at the monitor and temperature control box as they are installed on a normal liquid insulated transformer. So here we can see our liquid insulated transformer. We go on to the left hand side. We can see control box, as we saw on the other three D model on we could see the thermometer is now mounted onto the tank. This is slightly unusual. Normally, thermometer would be mounted in the middle of the tank directly above the core and wind ing's. The reason it's mounted in the middle of the tank above the core on wind ings is simply because of the highest temperature. What we refer to as the top oil temperature is going to be in the center of the tank directly above the core and wind ings, So the installation position on a lot of transformers would actually be approximately where my mouse is. No, this is referred to his top oil temperature. It is a direct measurement on. We can then use this direct measurement to estimate the hot spot temperature. The hot spot temperature is the highest estimated temperature within the transformer, and it is within the low voltage wind ings closest to the transformer court. So not only do we have the gauge installed on the top, which Mrs Top oil temperature. We can also estimate the hot spot temperature by taking the top oil temperature, Andi then adding a bias or a temperature adjustment. In the past, it was not possible to install any former temperature monitoring within the wind ings themselves. However, that has recently changed and it is now possible to install fiber optic cables within the low voltage wind ings close to the core, and these give a accurate reading off the hot spot. However, many transformers do not take direct hot spot measurements from the low voltage wind ings, so instead they will have a thermometer mounted onto the top off the tank. On this thermometer will sit within a small well off oil. It will measure the oil temperature and the well itself is actually surrounded by resistor . As the transformer is more heavily loaded, the resistor will heat up as it takes a proportional amount of current on this wall. In turn, heat up the thermometer on. We get an indirect measurement off the hot spot temperature as he transformer is no longer heavily loaded. For example, if it was loaded, then the amount of current going to the resistant would be less on. This would give a indirect measurement, saying that the hot spot temperature should also be less. The whole resistor arrangement is only there to estimate the hot spot temperature. As for many transformers, the hot spot temperature is not measured directly, so topsoil measured directly from the top of the tank or sometimes from the side on the hot spot. Temperature is measured on modern transformers with fiber optic cables from the low voltage winding directly, or if not, it is measured from the top of the tank. Andi, this measurement has a resistor around the thermometer, and the resistance will heat up or cool down, depending on how loaded to transform race. This is an indirect form of measurement for the hot spot temperature on Once again as resuming, we can see all I cut ins and cut outs, and these will be used to activate things such as fans, pumps, alarms and shutdowns. For example, this particular transformer as four fans on If the transformer was to reach, for example, 80 degrees it may be the fans start and they will begin to cool the transformer down. This will allow the transformer to increase its cavey a capacity by up to 25% so the additional cooling is very useful when transformer capacity varies. However, the transformer is not designed to run continually with the fans on as part of a general inspection. It is always worth checking that the cut ins and cut outs are operating correctly and, if possible, to remove thermometer Andi, check within oil bath or something similar that the thermometer he's giving a accurate measurement. The accurate temperature measurement should be indicated on the dog age locally and also remotely 24. Gas Actuated Relay: today we're gonna look at a book holds. Relate that book Oath Relays are fitted onto electrical transformers. Specifically, liquid insulated transformers on the type of liquid insulated transformative it's fitted on is called a conservative type. Conservative can be seen here on the right hand side. You know, in the middle, that's this tank here on the name tank. Is this tank here? When we can see the book holds, relay is mounted between the main tank. What comes out here on goes to the book 03 late and then to the conservative tank. So it's mounted between the main tank on the conservative tank on the book. 03 Late is a form of protection fitted to these large Kaveh or envy a type electrical transformers. It actually has free functions on going to show you now what? They are using an animated three d model. So let's just skip over to the next model you can see here. Is that because it really again on what we've done this time? We've taken a cross section and we can see some of the other components on the top here, such as an air bleed or gas plead terminal control box on. We've also got a narrow here, signifying that that is coming from the main tank on the right hand side, on going up to the conservative tank on the left hand side. That's a look at that looks. In real life. We sweep back to transformer model again. We'll spin that around on. There we go. So it's coming out of the main tank trying. Line this up correctly. Excuse me, Main tank here along their on going into the base off he conservative tank, which we can see he's there and into the conservative tank. So what is it doing? Let's have a look. Well, gas, as you can see on the right hand side, flows out on along this point from the main tank to the conservative. Normally, there should not be any gas within the transformer itself. Most off the gas, such as oxygen or nitrogen or sometimes maybe hydrogen, is what they refer to as dissolved gas. There's actually around nine different gases that you could potentially find within the transformer. On the analysis of these gases is called dissolved gas Analysis or D G. A. A short generally if you're transformer does not have any fault, Then you should not be finding any large pockets of gas coming from the transformer tank. But what does happen is when we do have faults within the main electrical transformer tank . So this could be between the wind ings and the core between the winding themselves. Those small electrical discharges will heat up the insulating liquid on it were causing too late liquid to break down. When the insulated liquid breaks down, it actually produces gas is now the severity off. The breakdown dictates which gases are created. In other words, if you got a high energy discharge, this means I have quite a large fault within the transformer. What you'll actually have is a production off, for example, a settling now settling and ethylene. They take quite a lot of energy to make. That means you have to have quite a large fault within the transformer, and that is what creates these gases. When you have lesser faults or faults with not such a large amount of energy, then you will produce different gases. But the key points remember here is that any fault, small or large or medium, is gonna create some sort of gas. Now the amount of gas is very interesting and worth analyzing. So you may get a slow trickle of gas coming out of transformer, which means you ever low part of discharge, maybe within the transform myself in this low energy fault creates gradually more and more gas. However, you may also get a very large fall on. This sudden fault creates a lot of gas very quickly. So let's have a look at a book. All three low protects against this type of situation. So let's go over to left here. We've got a upper float, which is this one here? Got a lower float, which is this one here on. Then we've got a baffle plate, which is this red being pushing the love right down here. So let's imagine for a moment will go back up here to a note. Large electrical faults. The upper float maybe drops. The lower flow drops. The baffle plate pushes the lower float down. So that's the first kind of fault we're gonna have. This could be a large electrical fault on what's happened is this large electrical fault has created a lot of gas in a very short amount of time on because these gases racing down the pipe, what is going to do is impact. With this baffle plate here, you can see it's got quite a wide of edge on it. It's gonna push against that baffle plate on then that is going to force. The lower float down so massive in russet gas pushes baffle plate down, pushes the lower float down on. Then that is going to shut down the transformer, Mozer said. Shut down, obviously, is gonna be in alarm as well. But we're gonna shut down the transformer because that is telling us that if the upper float is up and it's just a lower float down on the baffle plate, which is sort of pivoted and pushed a lot of fight down, those combinations are what tells us that that is a big fault and we need to shut the unit down. However, there's other faults that we can also detect using the Buchholz relay again. We're going to use different combinations off floats and the baffle plate. The baffle plate itself is now no longer used. It's only there to detect large electrical faults and to push the lower float down. So now what? We're gonna uses the upper and lower float. Let's just push play again. Okay, so now we've got small electrical faults, assuming so you can see that up. The float drops lower float. No movement, baffle plate, no movement. So what's happened here? The baffle plate hasn't moved because what's actually happened is the lower flow has dropped on. The reason it's dropped is because the gas has been slowly trickling in in si years, says small electrical faults. So the small electrical faults this. Just imagine it's a winding to winding. Maybe it slowly over time, just kept trickling gassing. And as the gases get trickling in its built up within the chamber until it's moved down, down, down, down is displaced the liquid. Andi As the liquids being displaced, the float has dropped down because the flow is buoyant, so the float is dropped down on that has been set off alarm. We can see here to context, context, talk in context of the bottom on those contacts when they're separated yourself in alarm. So we know now that we've got a slow accumulation of gas hands that has self inappropriate alarm notice I said here along, we're not going to shut down the transformer at this stage. We just know. Okay, the transformers obviously got fault, and we need to find out what that is. So what we'll actually do is we'll go up here on Maybe we'll bleed some of the gas off using this valve. Well. Been send that gas off for analysis to determine how severe fault ease. Andi. Different gases also indicate where the fault is within the transformer, for example, cover monoxide or CO. Two is typically associate ID with the transformer insulation for the winding insulation, paper insulation or cellulose insulation is also what it's referred to, so we'll analyze that, and then we'll get a better picture of what's happening within a transformer. Never go back out. We've got one more type of fault that's just pushed to play, but again, Okay, lo insulating. Liquid level upper float drops lower float drops on baffle plate. No movement. So again, different combination year. But a different kind of fall so low into letting you could level up afloat, drops more afloat, drops on the baffle plate we can ignore like said, it's unusual. One type of fault. You just make sure that's place the end. Okay, I'm gonna back up a second to see, actually what happened? So this type of fault, see, the lower floor has dropped. So now we've got another float. That's drops on day lower float. This dropped now the upper flow. If that itself on alarm due to gas, what would happen is the lower flow would not drop because at some point, I guess starts to trickle into the conservative tank. We can see here through this pipe. So what will happen is the lower float will not drop due to a small electrical fault within the transformer in the gas accumulating of the time. However, it will drop when the liquid level within this by drops low. Now, remember the tank. We go back to her model over here. The tank is below the book Off relay on. What you have to imagine is below this section here, well below the top of the tank. Everything should be covered in the insulating liquid as what's called a liquid immersed transformer. I go inside actually might be able to show you here. We can see the connections here from the bushings. So this whole tank, this whole area should be totally flooded with liquid or insulating liquid. If, however, we set off that flow alarm within the book, all three late and we've got a problem because we know we're losing liquid. And that is a big issue that could lead to what's termed a catastrophic failure. And that's what we don't want. So what we'll do, we'll have this second lover float here on that will set off Onda alarm. In fact, it will actually set off an alarm and shut down. So this another shutdown trip remember the baffle plate pushing the lower float down was one shutdown on. Now we've got to floats dropping together the top on the bottom. That's another shutdown. So it's a shutdown scenario, and it means we've got low insulating liquid in the transformer. If that happens, then we have to take action immediately and find out what's going on 25. Load Tap Changer: today we're gonna look at on on load tap changer. What you can see in front of you now is a typical on load tap changer. It will be installed in a liquid immersed transformer. Typically, the insulating liquid is mineral oil. On it will have over its own compartment in which it will sit within mineral oil. Or it will sit in the main tank of the transformer with the transformer court on wind ing's . Now, as we conceive, we've also got some wiring connections here, but see connections connecting to each of the secondary warnings on these air connections. For each phase that's been around here, there would be, Hey, phase here, another one there, another one connecting to these cables and center of the screen there. That's three separate phases, and they're all on the secondary side of the transformer, and we're gonna use the tap changer for regulating the number of turns on the secondary. Y Ning's now, for those of you who are aware terms ratio on a transformer is also associating with voltage ratio. And what I mean here is Thea amount off a conductor that is within a magnetic field for a change in magnetic field will dictate the amount of voltage that is induced within that conductor. So in other words, if you've got a secondary winding with 10 turns, less voltage will be induced. Then if we had a secondary winding with 20 tones, so the number of terms within the changing magnetic field dictates him out. Conductor within the change of magnetic field on this ultimately dictates in our vault ease that is induced within the conductor. So we will use the tap changer for changing the number of terms on the secondary whining and thus changing the output voltage. That's all the tap changes doing because the tap changer is an on load tap changer. Doing this is not particularly easy. Changing the number of terms on a secondary winding when you're operating 100 10,000 volts or potentially mawr is actually quite difficult. So we need to be able to do this when the transformers online, and that means we need to break and close the circuit without interrupting it or causing it to trip. There are two main designs today employed for on load tap changes, and they are resistive Andi reactive types. The largest problem that you're going to have with a tap changer like this is simply that when it changes position on opens or closes a circuit, these spark or the ark, as we call it, is going to gradually wear away the metal contacts. This is the equivalent of switching on and off the light switch, but doing it at 110,000 volts or higher. And whereas you can switch your light switch on and on and you can do this for a very long period of time and the contacts they're probably not gonna wear away. That is because spark or the ark has very little energy. Where is on a tap changer? There is a lot of energy. So these contacts where you open close them to change the number of turns on the wind ings . They have to be very strong. Typically, when you're looking at a tap changer, the thing that you need to pay attention to is the number of taps. The number of taps are typically used to indicate when the unit should be maintained. On a typical number, life 70,000 taps would indicate that it's time to take the tap changer out and service it. If you do go to this model, you can check out the wiring configuration off this tap changer. That is, It's all when you scream. No. 26. Off Load Tap Changer: today we're gonna look at a de energized tap changer also referred to as an offload tap changer. And I'm gonna explain to what it is and how it functions. Offload tap changes are installed on electrical transformers. And let's have a look at some of the components. Quickly we can see here we've got a dark age. You some numbers on 123456 and seven. And then at the back here, we've got a rack and pinion type of arrangement. That's these funny shaped teeth. Onda. Above those, we've got some pins that stick out these air actually used for electrical connections On underneath. You can see we've got a metal plate which will be making and breaking circuits as it travels along this gray metal plate. In other words, as it is pushed along by the rack Continue. So let's have a look now at how the whole thing works so well, change positions. Just go over here. Okay, so you can see is moving along this rat as the handle is turned. Now the handle is usually manually activated and sometimes you'll see that the tap changer is padlocked to stop people moving it when they shouldn't be, especially if it's energized. That's exactly when you did not want to move it. We can see that the movement indicated on dark age is actually proportional to do. Now the rap is pushed along the metal plates. We'll see you again to free 456 and seven. Okay. Another thing to notice here is as it's moving along the metal plate, which is this one year that connects these these pins that press on to it. See one pin is pressing onto it, and another one back on that metal plate is pushing onto those two pins as it moves along. Is now no longer prison on those two pins is pushing on this pain here that you can see the front on also the him, which can see slightly towards the back on the right hand side. What's happening is that the tap changer as it moves is breaking on, making circuits or breaking a making a circuit. And I should actually mention here that when we talk about breaking and making a circuit, this is de energized tap changer. So when you are moving in, the circuit is not of sea life. But as we move along, we can see we're changing the wiring connections slightly instead of being sort of on this one in the top left hand to the other one on the left. Now it is as the plate has moved, going to the pin on the left and the pin on the right. And if the plate moves again, it is now connecting the been on the right with the thing further away. That one there. Now each of these pins are connected to wind things on a transformer. Andi as it's sliding along the pins, we can see. It's also doing it here on this connection on Also here on this connection free face transformer. Each of these pins are associate ID with a single phase on electrical transformer, and as it's moving, it's actually changing the turns ratio on the wine ings of the transformer. What actually mean here is each of the wind ings is made up of a certain length off conductor or a certain amount of turns on the whining, and as we rotate the tap changer, we are varying. We're changing the left off the conductor. Well, the number of terms on the winding now. This is quite important because if we can vary the number of turns on the wind ings, we can also vary the output voltage now going to specify here that the wine ings that we are varying are these secondary winding things were varying the output voltage. So this is not for the primary winding side. This is actually for a secondary one inside, and by varying the number of terms in the winding, we can vary in voltage output. Now, if you know anything about mutual, and doctors will actually know that if a conductor is placed within a magnetic field or a changing magnetic field, we will induce a voltage in that conductor. And that's essentially what we're doing. We're changing the amount or the length of conductor within the magnetic field by changing the number of turns within the magnetic field. So if we can add MAWR terms, then there's gonna be more turns within that changing magnetic field, which means we're gonna induce more voltage. If we decrease the number of turns within the change in magnetic field, then we will decrease the voltage. But that's essentially what the tap changer is doing now? We're doing this all manually. Her hand on larger transformers. You won't be doing this manually per hands. You'll have a automatic tap changer on. This is known as an on load tap changer. 27. Transformer Maintenance: So let's now have a look at General Transformer maintenance. The topic off transformer maintenance is very large, and it's beyond the scope of this course. But what I'm gonna do is set up a separate course on. We're gonna go through all of these maintenance tasks in much more detail. Look at the pros and cons. What I'm gonna do now is just read through the bullet points from 1 to 8. But very mind that not all of these maintenance tests on inspections etcetera will be relevant for your type of transformer. Dry type transformers require relatively little maintenance compared to conservative type transformers. So let's hurry through the bullet points first. And I could give my own personal opinion at the end. Number one transformer tank visual inspection to thermometer inspection, calibration and testing free oil level indicators. Inspection and testing. Four pressure relief devices. Inspection and testing. Five sudden pressure relays inspection and testing six gas actuated and book. All three lays inspections and testing. Seven transformer bushings. Inspection and testing. Eight insulating liquid sampling and analysis. So that's the liquid and most transformers only. Okay, so the general idea where transformers is that you want to be testing and inspecting them in order that you can determine the condition off the transformer. One of the big trends of the moment and I personally think it is a very good trend is what they refer to as condition. Monitoring condition. Monitoring requires things such as infrared photographic inspections. That means someone will go around the transformers with a demographic camera, and they will inspect the transformer on before hot spots, depending on the lighting as well. They may also find things such as tracking on the bushing or corona. The other benefit with tomography is that they can see things such as cooling issues or fouling on the heat exchangers. If one of the heated changes shows very little temperature variation across the heat exchanger, then we know that the heat exchanger is perhaps blocks or fouled. So when we do thermo graphic inspections, we can see all this without actually going into the transformer enclosure. So when we do photographic inspections, we can get all of this information without needing to shut down the transformer. Andi, if we are outside, we can even do this behind the fence. So we're not going into the transformer restricted area, in addition to demographic inspections. Also possible to do ultrasonic inspections. That is where we can listen for tracking on the bushings. And if there's any partial discharge around, the transformer will also be able to hear that as well. Providing were pointing a listening device in the correct direction. Soil sampling and analysis is very important for conservative type transformers. We can take all samples to send off to a laboratory on the labral and tell us some off the gas content within the oil. Well, perhaps the moisture content within the oil on many other factors, we can use these factors in to determine if the transformer is healthy or if it has a fault . We can even see if the transformer is running too hot or not. We'll actually see elevated levels of carbon monoxide and carbon dioxide within the oil or within the insulating liquid. And this tells us the transformers running hot. So analyzing Andi sampling the oil is very, very important and obviously we can do this with other insulating liquids, not just oil. Most of the bullet points are simply inspection on testing, and it is important that perhaps once a year, All your protection devices, especially critical protection devices, should be tested. It's not enough purely to assume that they are still functioning. The book also relays essential that should be tested periodically. As with the pressure relief devices, temperature monitoring on door level indicators. They don't just assume that these are working all of these protection devices because they may not be your oil level indicator. If it is mounted to the transformer tank via a small pipe, the pipe, maybe blocks you're a little indication may not be correct. Your book All three late perhaps the internal parts or the floats are rusted, and they won't drop as they are supposed to. So it's very important that you actually perform a real test or simulate a real test as much as possible. Obviously, this is not something that you want to be doing if you're not 100%. So what you're doing really do need to know what you're doing, and if you're not certain you should get an expert contractor in on, these people will be doing these sorts of tests and inspections every day, and they can then certify that each your protection devices is working correctly, I should mention that testing is something you can contract out. But the inspection yourself is normally what you can do on, for example, a quarterly or free monthly period oil level. Indication you can check just by going to the transformer and trying to get a look at your level. Indicator the bushings, the tank, the thermometer such as temperature indication. You can also check all of these when you are walking around near the transformer. You're looking for anything that is slightly unusual, such as leaks or perhaps the temperature gauges indicating transformer is very hot when it should not be so anything that is slightly abnormal. In addition to that, when you're walking around near the transformer, also, listen, you're here. If the transformer is not functioning correctly, it should be making a light humming noise on this humming noise will become louder as the transformer is more and more heavily loaded. I've been to some plants, actually visited one in Eastern Europe. Onda. We could actually hear a almost crackling radio sound as we were walking around the transformer. This is obviously not very good, and it's the one time I was very, very happy to get away from that transformer. A crackling, static, electrical sort of discharge noise in the air is not what you want to hear when you're walking around near the transformer. As I stated earlier, though, the level of maintenance depends upon the type of transformer dry. Tens formers require simply less maintenance than liquid insulated transformers. A dry transformer. The vehicle inspection could be to clean the transformer when it's obviously not life and, if possible, to test devices such as the temperature monitoring on the temperature alarms and shut down . Another important factor of maintenance transformers is simply the cost, a high value asset. In other words, a transformer that is potentially worth a lot of money on, if it fails, will also cause a lot of what we call business interruption. That means that the whole business was shut. Now he's going to receive a proportional on our funding for maintenance, or it should receive that. The reason is, if it fails, it may potentially cost the company or the institution hundreds or tens of millions of dollars. So this loss far exceeds the cost off. Having a spare transformer there on may be applying some maintenance, however, for other smaller installations, such as a general plant where they manufacture maybe aluminium or steel. If they don't maintain a spare, it might be because they have enough capacity installed where they could bypass that transformer. Or it may simply be that we transformer could be obtained easily on the market. Spares are readily available, and the final reason may simply be that the loss of the transformer may not impact the business significantly. And if that's the case, then they may allocate less funding for matrons to that transformer, and they will put more funding into another transformer that has a higher criticality. So it really does depend on the type of transformer on how critical is within the system. It serves. As I say, I'm gonna produce a totally different course for this. So I believe it's a very important topic. I actually designed a free tool. It's called truffle and see on the bottom here, free online transform asset management tools are available. A truffle that come. If you want, you can go there, check out the pdf check out the tool. The transformer tool has actually been downloaded over 5000 times. Now Andi. I am continually improving it. Let's get on to our final lesson now about what I refer to is transformer killers. 28. Transformer Killers: So let's have a look now. What are referred to his transformer killers? I know the name seems slightly strange in a technical engineering sense, but these items that we're gonna refer to in a moment are essentially the three main killers of transformers. So let's have a look. If we go down one off the killers, you want to call it. That is overheating. Many, many transformers that have seen have suffered from overheating. Overeating is one of the main reasons, or one of the killers of transformers oxygen. This is for insulated transformers only, or liquid immerse transformers that is another killer. The oxygen content becomes very higher. Next. This leads to a array of problems, which will discuss in a moment and moisture in other words, water. And again. This is for liquid immersed transformers only. So let's learn a little bit more overheating. Overheating is the most common pours for transformer damage. He could even be classed as a serial killer. Overheating leads to damage of the winding insulation on potential damage to the liquid insulation. Both of these factors drastically reduced the health of the transformer, and it's used for working life, typically 20 to 25 years. Oxygen oxygen, combined with high temperatures and a copper catalyst which is twinings, usually may produce sludge in the insulating oil sludge is actually the remnants of insulation paper on oil that have degraded due to the effects of heat, oxygen and copper wine ings. Acting as catalyst sludge can occur without elevated temperatures as it is theocracy izing of oil. That is the true problem. Elevated temperatures accelerate degradation. Sludge compromises the dialect extract for the all and reduces the transformers ability to cool itself, which leads to elevated operational temperatures, which may create more sludge and worsen the condition. Still further. Moisture moisture within the insulating wall reduces insulating properties of both the paper on Doyle. This reduction insulating properties allows minor electrical faults to occur, such as partial discharges, and these come progress into potentially severe electric faults. The location of the moisture within the transformer is temperature dependent. A warmer transformer will liberate moisture from the paper insulation, while the colder transformer will allow moisture to migrate from the oil into the paper so we can see these are the three main killers overheating options in a moisture when we can also see that sometimes they worked together, for example, overeating an oxygen in order to exasperate or make a problem even worse. If you can control these three main factors within a transformer, then you are on the right track to maintaining a healthy and happy electrical transformer. Overheating itself is a big killer. Whenever you see a hot transformer, you have to ask yourself, Why is it running hot? And is there anything you can do to reduce the temperature that is operating at now? This may be simply blowing more air across the transformer. If you have a dry type transformer all, perhaps you need to clean the heat exchangers if you have a liquid immersed transformer. Or maybe it's putting the transformer within some sort of transformer vault so that it remains in the shade. There are a lot of different factors, but overeating is the biggest problem you ever gonna have for the transformer, and you should avoid it as much as possible. Oxygen and moisture are problems associated with liquid. Insulate transformers on. This is the reason why you should do a little analysis or why you should sample the insulating liquid if you have excess oxygen or excess moisture. You're gonna be able to notice that when you sample the liquid. So I recommend you do that. That's pretty much all I got to say for this course. I suppose Now we can get on to the next lesson on do a short summary. 29. Final Thoughts: So that's it for this course. I really hope you enjoyed the course and you found it quite interesting. And you will find it useful. If you've got any questions or comments, please do. Let me know. I'm more than happy to get in touch, help you with whatever you may be struggling with. If you've got any feedback concerning how it can improve the course, please do let me know. We'll definitely consider it and apply it if possible. Once again, thank you very much for taking this course. I know there's a 1,000,001 other things that you could have done with your time. And I'm very thankful that you did chooses course on that. You've supported me and helping me produce more and more content. So that by from me hope Sian next course 30. REFRESHER LESSON: Transformer Parts and Functions for courses: in this video, we're going to look at the dry type transformer, the hermetic type transformer and the conservative type transformer. We're gonna look at the transformer components such as the core and wind ing's. And then we're going to look at some of the other components that you're likely to see, such as the bushings, gas actuated, really temperature thermometer on the dehydrator breather. So let's get stuck writing, and we can start by looking at the heart of the transformer, which is the transformer core. So here we have a three D model of a transformer core. We'll do a little spin. As you can see, this court has three limbs on. These three limbs indicate to us that this is a three phase transformer. The top on the bottom off the transformer core are known as to yoke on. These three pieces in the middle are known as the limbs. Each limb correlates to one face off the transformer. The core itself is clamped together, usually using a TC of awesome straps. We look on the bottom here, you can actually see. There are three straps thes items here, and you'll see there's also straps on the other side 123 So the transformer core is clamped together, and the reason it's plant together is because the core is No. One solid block of metal. It's actually a series of metal sheets that have been clamped together. You'll actually call these laminate steel sheets you can see on the side here that we've got these straight lines. These straight lines indicate to us that the sheets are of a different geometry. On Daz. You've clamp them together. You get this wavy pattern. If we can see or move over to another limb, you can also see over here. And that's because the cool is not perfectly cylindrical now. The reason that we clamped these very thin laminates sheets together is because we want to reduce the histories is on the eddy current losses, so we'll clamp all of the metal sheets together to form a limb on. Then we'll clamp the metal sheet pieces together to form the yolks that is to say, the top on the bottom of the transformer call. Now each of the sheet is insulated from its neighbor on The reason we do this is because we want Teoh completely insulate or isolate each of these metal sheets in order that we reduce the eddy current and history sees losses. When we have electrical current phone through the wind ings on the wine ings wrap around each one of these limbs. Then we create an electromagnetic field on the call is gonna become magnetized. The job of the core is to direct this magnetic field in order that we can get a high magnetic field density or magnetic flux. So that's what the core is doing. So we got our limbs. 123 got the yolks at the top, and the bottom of the core on the core itself consists of very thin steel nominations that have been clamped together and have been isolated from each other, usually by using some form of lacquer or coating. And then once it's all together, we're gonna clamp it together or perhaps glue it together. On that is our transformer core. The rest off the assembly that we're looking at now is simply to hold the core in position . So we've seen a section at the bottom here that is to secure the core in the base of the transformer to make sure he doesn't move around, and we can see at the top as well. We also have this installation to secure it to the top of the tank, and again this stops any movement off the core. Within the transformer casing, this type of core could be used for a dry type transformer hermetic type transformer were a conservative type transformer. The design does not change that much. The only noticeable change that you will see is if you're using a single face transformer instead of a three phase transformer like that currently shown. So now we've had a look at the transformer core. Let's go have a look at the next item on the list, which is going to be the wine Ning's. So now you can see we're looking at a dry type transformer. This is the type of transformer that is not insulated by liquid on the liquid, maybe oil, or perhaps some sort of synthetic oil or even a biodegradable type of oil. But either way, it's the dry type transformer, also sometimes referred to as a cast brazen type, Transformer concedes, got wheels on the bottom for moving into position on. We've got these great BC's these are for cooling the transformer. If we go up, we can see the connections on the back of the transformer. But if we break it down into its components, you can see there are quite a lot off. Um, there's a core again, as we were looking at earlier. We'll see if I can actually assemble it slightly. We might see the actual shape off the course. It comes together. You could see there. There are the straps that we were talking about earlier these straps he used to clamp the core together, and we should be able to see the top of the core coming down at some point. Okay. The top of the court has now been installed. Unfortunately, get a good chance to have a look at it. And they're the low voltage connections coming out of the top. But let's exploded into its components again. So there's core and we can see here. All of these circular items are gonna be installed onto each off limbs. Remember, one limb is one face. So this is a free face transformer. Andi. Within this group, we're gonna have low voltage wind ings. Andi, High voltage warnings. The low voltage wine ings are going to be installed closest to the core. So they're gonna be wrapped around. We're very close to say to the core immediately after the low voltage warnings, we're gonna have high voltage linings. So we got a primary and secondary winding installed. And if we push the play button, we can actually see them coming down onto the core. He come back, clamps it comes some sort of insulated, most likely. And here comes and linings on the hate three warnings that go on the outside once. That's all the same board. It's gonna look a lot like this and we can see by looking at it back. What type of wiring configuration that transformer has the winding themselves are going to made off copper or aluminium? Aluminium is usually used if there is no consideration to space. If you have a lot of room, you can use an aluminium type transformer. Generally, they will be bigger than transformers that use copper for the wine ings. This is because the conductivity of copper is higher than aluminium on their ability to carry current is also higher. However, aluminium is cheaper. And if you've got the space. Then you can install a transformer with aluminium twinings. But just remember, low voltage linings. They're gonna be wrapped first around the core. High voltage wine ings are gonna be wrapped second around the low voltage Twinings themselves and then we're going to assemble the whole thing together. The one is themselves. They're gonna be out the copper or aluminium that is a transformer, as we have it. Now, the core and the wine ings are the most essential pieces of the transformer. Technically, you can even manufacturer transformer without the core, although will not be very efficient. The dry type transformer that we're looking at now is the simplest off the free that we're going to look at on this dry type transformer consists of only the core wind ings on some cooling fans on the bottom. Let's now have a look at a hermetic type transformer. So here we are. We're now looking at a hermetic, liquid immersed transformer. Have a spin we can see on the top that we've got some low voltage bushings that sees for thick ones here. The reason they are the low voltage bushings or the reason that you can tell is because the connections a very large the reason they're large is because the voltage is low on the current is high. So that's a giveaway. That the low voltage bushings are these four. Here we go. On the other side, we can see the high voltage bushings, and that would be these three year one to three to give away for those is simply the voltage has been increased. Therefore, the current has been reduced so we can see the current carrying pieces of the bushing. That's this metal piece here on this one. Over here, those pieces air gonna be a lot thinner because they currently carry is gonna be a lot less . However, the voltage is gonna be higher. And that is why they have mawr insulation than the low voltage bushings. So if you step on the voltage, you're gonna need more insulation. And if you step up the current, then you're going to need a thicker conductor minutes. Break this down into its individual components again. Just have a look. See what is inside the box. We can see there there is a transformer core again. Free limbs. That's three phase Got the two yolks one at the bottom, one of the top, and we have our bushings, and all of that can be assembled again to complete the hermetic type transformer. So since the hermetic dark transformer is a dry type transformer but with a box around it or a casing that is full with a insulating liquid. Now this insulating liquid is typically mineral oil. About 95% of time it's gonna be mineral oil on the whole thing sits in a bath off mineral oil. The reason it's called hermetic is because it is totally isolated from the atmosphere or from the external environment. If you think about it another way, just imagine it's a hermit. All of the parts within the transformer don't want to come into contact with anything else , a bit like a hermit who lives in a cave on a hill. So these transformers classes Semetic because the internal Bart's don't want to come to contact with the outside. Once the transformers sealed in, the casing is sealed, he shouldn't be reopened again. However, there are exceptions to this, such as when you perform all analysis, etcetera. But this depends upon the manufacturer. We've already discussed the bushings Let's have a look at a few other items that we can see . We've got a filling pipe that would be this area here. We've got some lifting bolts or some lifting eyes. That's one two on another two on the other side. So that's for positioning the transformer or for installing it is the other 21 to, And then we got a temperature indicator. Do you mean we can see it here? And that's gonna measure the temperature off the insulating liquid, which again might be mineral. Or perhaps it will be silicone. Or perhaps it will be some sort of synthetic Easter, which is more or less a biodegradable oil manufactured from plants. We do now, we concede indicating itself is not perfectly square. It's got these fins attached to the side. These fins are used for cooling the transformer. What's actually gonna happen is that some of the insulating liquid is going to absorb the heat generated by the transformer, and it's gonna pass that heat on to the fins and the things going toe pass the heat on to the air. So the reason for the fins is to increase the contact service area between the tank and the air on this means we're gonna get a much higher he transfer rate if we can keep the transformer cool, and we can also load it more heavily, at least up to a point important to realize that if you can keep the transformer call, then you're also extend Its youthful working life. Overheating is typically one of the big killers of transformers. Let's now have a look at the conservative type transformer, which I think is the most interesting and has a lot more components compared to the drying , hermetic type transformers. So here we are. We're now looking at a conservative, liquid immersed transformer. The reason it's called a conservative type transformer is because of the tank on the back, which is known as the conservative tank. That is this item. Here we can see the bushings passing through the transformer casing on pointing upwards. As you can see on the left side. There are four high voltage bushings on three low voltage bushings. The high voltage bushings have more insulation on the low voltage bushings have less insulation. The purpose of the Bush's is simply to connect the internal winding of the transformer to the outside electrical circuit, and we want to do this without raising the electrical potential of tank itself. And that's what the bushings allow us to do. They allow us to pass the cable through or to connect the electrical circuit from the inside to the outside without raising the electrical potential off the transformer tank itself. Let's go over. Try Conservative tank again. The conservative tank is installed to allow for expansion off the insulating liquid when it gets heated up, or when it cools down the transformers heavily loaded, then insulating liquids gonna heat up. Andi, it's going to expand upwards when a transformer cools down, the insulating liquid is also gonna call down on. Then the insulating liquid level is also gonna drop. So as we heat up the insulating liquid, it's gonna expand on as we call it down. It's gonna contract in order to know what the level is. We install a mog and this is a magnetic or gauge. We can see the temperature at 20 degrees. We should have this level, so if we have 20 degrees now, the level will be here. As the temperature increases, the level will increase This is not a temperature gauge. This is a level gauge. The 20 degrees Celsius is just for reference. What the level should be at that temperature. If we look also on the bottom, we conceive these two red lines for two red triangles. These are used as low level on DLowe, low level alarm set points. It's important that we maintain a good head of insulating liquid within the conservative tank, because if that level drops down, we could get a catastrophic failure of the transformer. And obviously, this is not what we want. You look inside, I can show you the working lever, a very easy lever. Will the float and you can see that as the level would increase, the float would be pushed upwards, and as the level decreases, the float would sink back down again. So that's how it works. Just remember, though, that this lever and flow is no connected directly to the outside gauge. It's actually connected magnetically. It's coupled magnetically. That's why it's called a magnetic oil gauge. So we have a form of level measurement here on the side of the conservative. But there is also an interesting component fitted below the conservative on this is known as a dehydrating breather, sometimes called a silica breather, because it uses silica gel. As the transformer heats up, the liquid is going to expand. The insulating liquid is gonna expand. And we're gonna push air out of the conservative tank, and it's gonna come out through silica breather. Just go up and see if I can find the holes where it comes out, okay, so we can see the holes in the side off. The breather on the air is gonna be pushed out for these holes because the liquid is expanding in the conservative tank, Andi is gonna be pushed through the silica gel breather on then, out of these holes toe atmosphere when the liquid cools down because the transformers perhaps not so heavily loaded, we're gonna draw air back in through these holes again on. Then it's gonna be drawn into our conservative tank. And that is the problem. If we're drawing air directly into the conservative tank, we want to ensure that it does not contain any moisture. If it does, we're gonna get a problem. This may lead to a build up of sludge. When the moisture comes into contact with oxygen. Not only that, but a die electric strength for our insulating liquid is going to be reduced. So these are all negative effects. So what we'll do, we'll pass the air through a silica gel breather. What is this item here full of silica job? Eat on the silica Joe Bees will remove the moisture from the air as they removed the moisture. Guns changed color. And when the color is changed by 3/4 we know it's time to change the silica gel beads, so the color changes purely for a visual indicator to see how saturated the silica gel beat are. Once the air has been dried, it's gonna pass into a conservative tank. There is one other interesting aspect of the silica gel breather with the dehydrating breather, and that is the oil cup on the bottom. And this is used to separate dust particles as the air is drawn in Ondo through the breather. So we use this oil or the oil cup to attract bits of dust, and as the air bubbles through the oil, we're going to separate the dust particles or foreign bodies from the Airstream, and that's going to ensure that we don't get any dirt or dust going into a conservative tank on mixing with the insulating liquid. So the dehydrated breather consists often or cup for separating dust particles and other foreign bodies on a silica gel, bria or a dehydrating element, which is then used to remove moisture. The reason I call it a dehydrate sometimes instead of a silica Joe breather is simply because the dehydrating medium may not be silica gel. It might be something different, so don't always assume it's going to Silica gel is just a silica gel is used 90% of the time. Let's now have a look at one of the most important pieces off the transformer. On this is the gas actuated relay, the gas actuated relays contained within this square box. You may also heard a turnbuckle freely, although the book all Trillion and Gas actuated really a slightly different. The gas actuated relay protects against small electrical faults within the transformer on large electrical faults. Within the transformer, a book or three late protects against smaller, large electrical faults, but also against a low insulating liquid scenario. So if we have a small electrical fault within the transformer. We're going to heat up the insulating liquid on this is then going to generate small bubbles of gas. Small bubbles gas are going to slowly accumulate within the book. All three lay you're gonna push a float downwards on. Then we're gonna set off an alarm which tells engineers that there is a small electrical fault within the transformer. If we have a large electrical fault, we're going to get a sudden increase in pressure on a large pocket of gas. This pocket of gas is going to rotate a paddle and that is gonna shut down transformer. Those are the two functions of gas actuated relating to alarm when we have slowly accumulating pockets of gas that caused by small electrical faults and to shut down when we have sudden large increases in pressure and gas that it created by large electrical faults . The book, culturally itself has 1/3 and final feature on that is to shut down the transformer. In the event the insulating liquid level becomes low. We can see that it's installed between the conservative tank on the main tank. If the level was to come down to here, we would tripped the transformer on that protects the transformer, then on ensures that we do not get a catastrophic failure. Resume out. You can see that we have different cooling things on the side of the transformer this time . The reason that these cooling things are larger is because we need to get rid off more heat . I'll just rotate around. The side can see that we've got a entire radiator. This time the liquid enters the top of the radiator, it cools down and then it passes out the bottom and we'll have a natural conviction in order that the process continues on. We can call down insulating liquid as much as possible. We go to the end. We can actually see that we've got some fans, and these fans will start once the temperature of the insulating liquid becomes quite high . I can see now that they're running, that means you're transformer is heavily loaded on. We need to pass air over the heat exchanger or the radiator in order to get a greater cooling effect. If the fans of running like this, or if we have fans installed, we will say that the type of cooling employed is forced air. The second type off cooling that is described would be there cooling associated with the insulating liquid itself. In our case, we have a natural conviction process. So this transformer is an oil natural air forced type transformer or O N A F as it will be written on nameplate. Go over to the end of the transformer on we can see we've got a control box. His control box or control cabinet is used to house some of the associated machinery with the load tap changer. The low tap changer is mounted in this section here on this type of tap changers mounted directly within the transformer tank. That's not always the case. Sometimes the transformer will be mounted externally. Or perhaps it will have its own compartment within the transformer tank. The disadvantage seven attack changer directly within the tank is simply that it shares the same insulating liquid as the transformer. That means that when you sample the insulating liquid and start to look for faults or telltale signs such as large amounts of a settling orry Thane, you're not gonna get much reliable information from your sample. If the tap changer is mounted in a separate compartment or externally to the main tank. Then you can sample the main tank. You can then send a sample away for analysis. You can look at the gases that are present within the insulating liquid, and that would give you a good indication as to what folks, if any, present within the transformer. If we go this way, we can actually have a look now at the final piece of the transformer, or the final component on that is a temperature indicator and temperature thermometer. It's the moment sir has been mounted within the tank. We can see it here on the indicators mounted inside, in order that engineers, as they walked past, can look at the temperature gauge on assess what it is. And if we're operating within normal conditions, The Red Needle itself is used as an alarm set point. If the Black Needle should come around and surpass the Red Needle, were guns getting alarm? The other red needles that we're looking at now I mostly used for cut ins and cut outs for fans on cooling pumps 31. Why Are Transformers & Generators Rated In kVA And Not kW: Hi, John. Here in this video, we're going to look at why generators and transformers a race is involved to Jam Pier on, not in what's in order to understand the problem, let's take a look at the equations associated with voltage ampere on what's voltage. Ampere equals a voltage multiplied by the AM pitch kilo voltage ampere equals a voltage multiplied by the and pitch divided by 1000. Let's now take a look at the equations associated with Watts and kilowatts. What's equals voltage multiplied by AM pitch multiplied by the power factor. If we're looking at kilowatts, it will do voltage multiplied by AM pitch multiplied by the power factor divided by 1000. We can see that the equations, the voltage ampere on what's a very similar. The difference between the two equations relates to the power factor. Now it is possible that if the power factor equals one, that voltage ampere also equals what's. However, if the power factory called one, then we would have no need to use what's because voltage ampere would also equal what's therefore. We can assume that the power factor is not the new Rule one. The power factor is defined by the type of load connected to the transformer, a generator, lo driver, resistive, inductive, capacitive or a mixture of these. Because transformer and generator manufacturers do not know the load to which the generator or transformer will be connected, it is not possible for them to define the power factor. If the power factor is known, a rating could be given in what's, but the power factor is not known because the load is not known. Therefore, it's not possible to give the transformer a generator orating in what's It's for this reason that transformers and generators are rated involved in Tampere. Now that we know why, Transformers and generators a rating in K V A and not OK w you should realize that motors can be racing and what's okay? W The motor itself is the end load. Therefore, his power factor is known. If we know the power factor, then we can easily add it to our voltage ampere equation in order to solve for what's This is the reason why motors are rated in what's whereas transformers and generators are rated in voltage ampere