Hello everyone, we’re happy that we’re all together again and this tutorial we will explain some basics related to the world of electrical engineering that will be the guide for us and the rest of thi[.]
Hello everyone, we’re happy that we’re all together again and this tutorial we will explain some basics related to the world of electrical engineering that will be the guide for us and the rest of this course Those are some very important fundamentals for anyone who works in the electrical engineering field Are you ready? Fasten your pill and let’s get it started The aim of this tutorial is to know what are the different ranges of the voltage that are used in the electrical field Also we will learn what is the relation between the different engineering parameters like the volage, the power, the current and so on So let’s go ahead Indeed there are some standard ranges of the voltage that are used in the different electrical applications And those different ranges are categorized according to some standards for us to know what are the types or the categories of the voltages that we are working with so the first category of range is the low voltage range which starts from volt and it ends at KV so if you are handling any value of voltage that is in between of those margins you are in the low voltage range at this condition Now, the second line is the medium voltage category that has a range from KV to 66 KV or some other standards consider the medium voltage to ends at 33 KV So anyway those are the ranges of the medium voltage also the third ranges-the high voltage range that starts at 66 KV and ends at 220 KV or 500 KV Also this is according to some other standards and for example when you know that there is a step up transformer that rises the voltage from 11 KV to 220 KV, so this means that the primary voltage of the transformer is a medium voltage and the secondary of this is a medium voltage and the secondary of this transformer is a high voltage or in other words we say that it’s a medium to high voltage Transformer Now the next ranges the extra high voltage that ranges from 500 KV to 750 KV and finally we have the ultra high voltage that ranges from 750 KV to 1,200 KV, so those are the voltage ranges map that can guide us for any value of the voltage to know what is the kind of this voltage that we are handling Now after knowing the borders of the voltage ranges, we need now to know some commonly used values of the voltage that are used much inside those ranges so the popular values of the voltage and the low voltage Zone as 120 and 220 V and also 380 V So those are some standard values of the volage that are used in our homes for the appliances to work on according to the American standards or according to the pre standard also the popular values of the medium voltage zone as 11 KV 22, 33, 66, 2.2 also 3.3 and 6.6 So the medium voltage devices or Transmission Lines use those values very commonly, while the high voltage popular ranges are 66, 132, 220, 400 and 500 KV, and for the extra and ultra voltage the most popular ranges are 500 and 750,1000 and 1200 But now you may ask why we need to have some standard ranges of the voltage that the world works according to them? So this is because the electrical devices like the transformers,the generators or the cables for example so they are designed mainly according to the voltage’s standards or those voltage’s standards so we must have some standard level of the voltage that the world must work according to them to manufacture those devices according to those standards that the world works on, but if we specified many standards according to each country or each group of countries at this condition, we must manufacture some electrical devices with many different standards to cope with many voltage labels and this will be an efficient solution Alright, now let’s move to the main electrical system parameter So the first parameter that we will work on of the electrical voltage is the active power and it’s unit as what, so it’s equal to the voltage times, the current times, the power factor if we are talking about the AC power So the power physical meaning is that it’s the electrical energy that an electrical equipment can consume or produce at a specific time suppose we have a motor rated of 2,000 W, so this means that this electrical power that this motor must consume to produce a specific mechanical rotational power as 2,000 W So it’s supplied by an electrical power to convert it to the mechanical power corresponding to this electrical power and also when I say that I have a power station with a power of 500 MW for example, so this means that this station has some generators that can generate an electric power of about 500 MW And this power is transmitted to the consumer to get the benefit from it by converting it from its electrical form some other forms that the user need like the lighting purposes or to operate some mechanical loads or for the factories loads and so on now after knowing that the power equals to the voltage multiplied by the current, we need to know what is the relation between the voltage and the current So we have two cases for the relation between the voltage and the current: - Firstly in case of constant power So at this condition The current will be inversely proportional to the voltage and this is logically true because of the voltage increases but we need to get the constant t power so with this condition the current must decrease to have the same value of a constant power and the case at which we have a constant value of power when we are talking about the power source itself as the power source has usually a constant value of power suppose that we have the same power station that produces a constant power of 500 MW Now if we are trying to transmit this power through a voltage range of 220 KV so it’s a high voltage range And at this condition The current transmitted will be 2.2 KA which is a small value Now if we try to transmit this power on the high voltage range of 66 KV which is smaller than 220 KV so with this condition, the current transmitted will increase to 7.5 KA instead of 2.2 KA, also another example if we have a constant power of 1000 W and we need to transmit this power through a transformer so at this transformer is a step up one and the voltage at the primary coil is 10 V and we have 100 A now if we step up this voltage from V to 100 V so the transmitted ampe on the secondary will decrease to 10 A instead of 100 A on the primary side so you notice that when the voltage increases the current decreases As we have a constant power conduction - Now the second case If we are talking about an electric load that consumes the power So we are not talking about the electric power source that supplies the power but now we are talking about the load or the device that consumes the power Now, this condition we will have a constant load with a constant power so the resistive or the impedance is constant and its relation is the volage over the current, now to get the constant resistance when the voltage increases, the current must increase for the resistance to remain constant so in that case of constant load the evoluges directly proportional to the current now the electric current has some properts and the most important of them is that is affected sectional area of the cable used so if we are designing a cable to carry a specific value of electric current so at this condition the cable cross sectional area will be designed according to the current that will path through this cable so the electric current is directly proportional to the cross sectional area and this is because the cable conductor is supposed to be at you which carries some free electrons of the electric current so if we have a smaller cross sectional area than what the electric current need to path through it So the path at this condition will be very narrow for the electrons to follow through the conductor and it will have some collisions with the conductor atoms which it produces and increase in the conductor temperature So there will be an excessive heat that produce in the conductor material and there may be a failure in the cable or it may be damage or burn out due to the smaller cross sectional area than it’s required On the other hand in case of we have a larger cross sectional area that is suitable for this amount of electric current to flow and to at so at this condition the flow of the electric current or the electrons will be very easy with no collations with the conductor atoms Now the final thing we have is the voltage designing conditions so if the current was directly proportional to the cross sectional area here the voltage is directly proportional to the insulation level this is because the voltage is nothing but an electromotive force so the volish can be represented by the force that those electrons are moving with so we must ensure that the insulation is sufficient enough to be stronger than the voltage level to ensure that the voltage force will not prey the insulation force like this case here and for this reason we can note that at the high voltage caples they have a large insulation level than the low voltage insulation level and this is because when the voltage increases the magnetic field produce from the cable will increase so we must surround this large magnetic field and this large electromotor force with the sufficient insulation level to avoid the case of break of insulation So I think that’s enough for this tutorial about some electrical fundamentals and at this point we have finished how basically right now thank you for watching and see you next tutorial