Transformadores de MEDIDA y PROTECCIÓN ⚡ ¿Qué son y cómo Identificarlos?

hello protons the time has come many of you have asked me to do it and now it's time for sure in this video let's talk about substations again and switchgear more specifically of instrument transformers and protection transformers let's go for the traditional current and voltage transformers do you know what a measuring and protection transformer is? did you also know that they are called instrument transformers you know what types there are and what they are used for or how to identify them in this video I will try to solve all these doubts and we will also go into into the world of instrument transformers and their applications to discover all this and much more follow my lead follow my lead this is the first of two videos dedicated to current transformers and voltage transformers here I will show you how to identify them and also how they work in the next video you will learn how to size them to do the little calculations that are necessary to know how to size them which instrument transformer to select so be attentive as soon as it is published I will link it up here and also in the description now I warn you we've gone crazy with these videos remember the electromagnetism and the three-phase series do you remember the thrashing we did in the channel with them? well with these videos we are back to work with a technical level to match so be patient and be well well well be attentive they will come out of here being experts in instrument transformers and protection if you study electrical engineering or work as an electrical engineer these videos are for you I have no doubt for sure many of you have crossed at some point in your studies or in your working lives with current transformers and voltage transformers the calculation and sizing of this equipment is key for the power systems are safe and reliable but they are also an essential tool for the measurement of the powers generated and consumed at the different points of the network and this in turn is the basis for electricity pricing let's find out how much consumers are charged and how much they earn the generators current and voltage transformers are the two major types of instrument transformers that exist the term instrument transformer seems quite intuitive are transformers used to measure electrical quantities voltage and current a bit less intuitive seems the other term with which they are called instrument transformer are called as follows because they are the ones in charge of giving magnitudes adapted to the measuring or protection instruments to relays to meters to network analyzers etc. current or current transformers provide an electric current proportional to the current to be measured the primary current voltage or potential transformers provide in their secondary winding a voltage or electric potential proportional to that of its primary winding which is the one to be measured what they both do is basically adapt the magnitude reading to a proportional value but much smaller so that the measuring or protection instruments are not fried by immense working currents but receive a signal that multiplied internally by a number by a value x can be translated to the real magnitude to be measured let's go a little deeper on this point because it is the key that justifies the existence of transformers measurement and protection transformers usually the quantities to be measured have very high values let's imagine a 400 kilo volt substation for example a node of the transmission network with huge transported powers and therefore high currents an instrument that would have to measure at that point the current carried by a line should have an insulation level suitable for that voltage level and in addition it would have to withstand the short circuit that can eventually go through their terminals and this of course would be very expensive equipment and very difficult to standardize instrument transformers are used to solve this problem since they constitute in themselves a galvanic isolation which allows the measuring device to be a low voltage instrument that works with reduced currents in addition to instrument transformers are manufactured with standardized secondary values which makes it possible to standardize the measurement instrument and not to have to design them in a particularized way for each project before explaining how they work and how they are classified I would like to make a parenthesis in your professional life. surely you will have to refer to them in English and in this case it's easy because the technical term is the literal translation from Spanish but it's good for you to know are called instrument Transformer which are the instrument transformers and also although less frequently masherment Transformer which would be a measurement transformer on the other hand the current transformers are Current Transformers which is also common to find them by its contraction c t and also the voltage transformers eh will be called walkits Transformers or potential Transformers and the contraction v t is usually used against the contraction v t now from a more practical point of view what international standards exist for instrument transformers by the international electrotechnical committee i s e we have the i s 61 869 standard which overrides and replaces standard 60 044 and consists of 10 parts of these 10 for the scope of this video we will highlight 5/1 general requirements for instrument transformers additional requirements for current transformers additional requirements for voltage transformers inductive additional requirements for combined transformers additional requirements for voltage transformers capacitors and coupling capacitors and capacitive dividers all these standards in turn have been adapted to European standards in and for the case of Spain to Spanish standards une across the pond the manufacturing standard is EI cube ansi c 57.13 2 016 Standard recalls for instrument Transformers as any of you can see if you navigate by these rules how to specify current transformers is totally different according to the chosen standard in this video let's focus on the definition according to the i s however I leave you in the video description as usual several links of interest to different standards and references one of them corresponds to a training booklet published by Arteche including a table of approximate equivalence between the transformers specified according to i s which is what we are going to see here and the transformers specified according to IE cube ansi having said that now let's get down to business what are current transformers as they are a special type of single-phase transformers which is specifically designed to reproduce under normal conditions of use a current proportional to the primary current in the secondary winding are designed so that the secondary current is out of phase with respect to the primary at an angle close to zero let's make the offset negligible so those are the two key elements let's play back a current proportional to that of the primary and at the same time hardly any lag are connected in series with the system to be measured and connect with the ammeter coils of the measuring device which have a very low input impedance which ensures that the current transformers work practically in short circuit to be able to identify them in a substation it is essential to remember that are connected in series with the system to be measured normally its appearance is similar to what we see in this image an insulator column supporting a small-sized equipment at the top the line driver enters and exits on its opposite side are composed like any transformer of a primary winding a magnetic core ovaries and a secondary winding ovaries the current to be measured flows through the primary winding and flows through the turns of the primary creating a magnetomotive force on the core the magnetic flux creates an electromotive force in the secondary windings if a load is connected to this winding a current i s will flow proportional to the primary current and this is the secondary current the magnetomotive force of the primary of a current transformer is counteracted by magnetomotive force induced by the secondary winding if for any reason the secondary were an open circuit all the magnetomotive force of the primary would be converted into excitation magnetomotive force producing extremely high voltages in the secondary which could deteriorate the insulation of the equipment and constitute a risk for the operators a good practice of the electrical engineer is to always specify short-circuitable terminals or terminals for current transformers these when any of its wires is disconnected terminals s one and s two are short-circuited thus avoiding the problem we were talking about are characterized by their transformation ratio KN whose expression is very simple as we see on the screen although it is more common to define them by their current transformation ratio which looks similar to this for example 400 split by 5A which is equivalent to say that when 400A circulate through the primary winding a current of 5A is induced in the secondary winding an ideal current transformer would have a linear transformer characteristic or what is the same would proportionally transform the primary current would have whatever value it is never saturates in any way because it is ideal let's represent on screen the tension versus current for any transformer as mentioned above if the transformer were ideal we would see that the characteristic corresponds to this linear region but ideal teams do not exist and the magnetic core in reality ends up saturating this is reflected in the elbow tension which is defined as the induced voltage from which a 50% increase of the magnetizing current only produces an increase of 10% in the induced voltage the area in which they should be used current transformers is therefore the central zone or linear region since the current conversion must always be proportional elbow tension for a current transformer for protection can be calculated according to the equation we see on the screen where k x is the precision limit factor RCT the internal resistance of the secondary winding of the RB transformer the resistance of the load connected to the same eh isn't the rated current assigned to the secondary 1A or 5A normally the elbow voltage is an essential parameter to understand the differentiation between current transformers for measuring and protection on the one hand the instrument transformers are connected to devices whose mission is to measure the current for information purposes a network analyzer for example or also for rating purposes what would be a counter these devices must measure the electric current being consumed under normal operating conditions and also very accurately for the primary currents in the range of the nominal operating current however if a short-circuit occurs in primary due to a fault it happens that the current to be measured is very high a failure of this type is not necessary to price it. and it could also damage the measuring equipment for that reason we are interested in that the core of the instrument transformers saturate with currents above normal operating currents and thus we will not damage the measuring equipment for those very high currents will be the protection traps on the other hand the protection transformers are typically connected to protection relays and their mission is to accurately detect possible faults in the system in order to trigger the necessary protections and clear the short circuit to accomplish this mission such fine precision is not required so fine so fine as in the case of the normal operating range we wanted to measure or rate but it is imperative that the transformer does not saturate when circulating through the primary the highest short-circuit current that may occur in that installation let's say that this type of transformation should respond well well well well to the fat spark we don't need to be very precise but we must be able to tolerate those large amounts of current which are the currents produced by a short-circuit after all in last place there is a third type of transformers that actually are a specific type of protection transformer these are the transformers for transients which have an optimized response in the transients of current that occur at the occurrence of a short circuit are used in special cases for some protection functions that need a lot of precision during these first instants in a similar way the current transformers voltage transformers are a special type of single-phase transformers specially designed so that its secondary reproduce a reading proportional to the voltage of the primary is the same what happened with the current transformers we are going to reproduce a proportional voltage and also the phase difference is going to be close to zero are connected in parallel with the system to be measured usually with a star-wye connection as in the case we see on the screen are connected with the voltmeter coils of the measuring equipment which have a very high input impedance which ensures that the voltage transformers work practically in a vacuum with very low secondary current there are two types of voltage transformers at construction level inductive and capacitive the inductive ones are the ones we have just introduced just now the capacitive ones on the other hand are simply an inductive transformer measuring on a voltage divider built with capacitors also include an inductive reactor to compensate the reactive power generated by the capacitors on the other hand the capacitive voltage transformers were developed because of the high cost to build inductive voltage transformers for high voltage applications however have a worse response in transient regime than their inductive siblings that's why they are not recommended for protective functions. with response in the first moments of a short circuit which is where this transient regime is these capacitive voltage transformers can also be equipped with carrier wave accessories for in-line carrier wave application but that's completely out of line of what is humanly possible to count in a single video so those devices are going to be left for later to be able to identify these devices in a substation it is important to remember that they are connected in parallel to the system to measure visually inductive voltage transformers are very similar to current transformers but only one conductor of the system reaches them on the other side capacitive voltage transformers are somewhat more difficult to identify they are equipment with larger dimensions which have two or more insulator bodies in column corresponding to capacitors that we commented before in the scheme and visually as in the case of the inductive ones only they get a connection from the high voltage system by the way very important do not confuse these equipments with the circuit breakers which have a similar shape but to them two conductors of the high voltage system arrive because they are connected in series now that you know how to identify them and that you can now distinguish well between the current trafos and voltage traps let's remember that instrument transformers can be instrument transformers or for protection we saw this very clearly in the current trafos but for voltage the difference is a little more diffuse on these voltage traps according to the standard and s all inductive voltage transformers manufactured must be suitable for measuring and therefore comply with certain clauses of this standard additionally some of them may be suitable for protection transformers intended for measurement and protection must comply with all the clauses of the i s regulations and this is the end of today's video but if you liked it, stay tuned in the next video we will define the accuracy classes of transformers as well as many other interesting features also from a practical point of view we will go deeper into the necessary calculations to select instrument transformers for each application either current or voltage with these two videos you are going to be able to select the instrument transformers or protection that you need for your installation hope you found it useful and interesting this video and without a doubt to contribute to your training as an electrical engineer and to the practice of your profession if you are already in that phase in this kind of practical videos we try to capture what is seen in our work in order to give you complete guides and visual guides that will be useful to you please don't forget to share this video with your peers and colleagues and also in social networks if you think it will reach him to someone who does this or is studying this kind of disciplines follow my lead is a reference place for 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Channel: Sígueme la Corriente

Views: 34,228

Keywords: Transformador eléctrico, Transformadores de corriente, Transformadores de tensión, Transformadores de Medida, Transformadores de Protección, corriente eléctrica, protección eléctrica, transformadores de tensión, cálculo de transformadores, dimensionamiento de transformadores, identificación de aparamenta, qué son los transformadores de medida, cómo funcionan los transformadores de medida, Sígueme la Corriente, Rubén Lijó, Ingeniería, Energía, Electricidad, Química, Física, Ciencia

Id: 8wPoXrjnNJk

Length: 18min 13sec (1093 seconds)

Published: Sun Feb 12 2023