A current transformer would hook up to this line here at a much higher voltage. They are designed to present negligible load to the supply being measured and have an accurate current ratio and phase relationship to enable accurate secondary connected metering. Current transformer ct construction and working principle. Ppt instrument transformer powerpoint presentation free.
Current transformers perform the following functions. Below is a list of all current transformers available through flexcore, however, not all models are instock. Download transformer ppt, free download transformer powerpoint. If the current measurement is carried out via two current transformers, the overall transformer ratio of the current transformers must be programmed into the measuring device. A current transformer ct is a type of transformer that is used to measure ac current. In part 3, were going to talk about current transformer ratio. Like the power transformer, the current transformer also contains a primary and a secondary winding. The current which would be at a much higher magnitude of current. To check pricing and availability for a specific current transformer model, give us a call at 614 8896152 or use our quote request form. It is similar to the voltage transformer but instead of transforming voltage it is used to transform current. The ct and pt step down current and voltages to a small val. Different model options are available from measuring primary current range of 50a to 5000a.
The current transformer will operate into either a short circuit or a resistive load until the voltage induced is enough to. A current transformer is an instrument transformer. Ppt transformer protection powerpoint presentation. It is a device used to measure large current by scaling large primary currents to a smaller, easy to measure, secondary currents. Apr 25, 2017 the current transformer the current transformer c.
So, primary current of ct assuming constant line current is constant irrespective of whether the secondary of. Mar 10, 2016 to start with, both are instrument transformers basically used for measurement and protection purpose in power systems. In part two, we talked about the polarity markings of a current transformer. Current transformers play an important role in the monitoring and protection of electrical power systems. It produces an alternating current ac in its secondary which is proportional to the ac current in its primary. In this post, we are going to learn what is ct, what is pt, what are the uses of ct and pt, symbols of ct and pt and also many important things about ct and pt especially why secondary of ct should not be open circuited. Whenever an alternating current flows through the primary winding, alternating magnetic flux is produced, which then induces alternating current in the.
Introduction to current transformers, part three, current transformer ratio. Current transformers cts provide a simple, inexpensive and yet accurate means of sensing current flow in power conductors. To confirm the physical condition and electrical characteristics of current transformer installed in the installation. Current transformerct and potential transformer pt are very useful and essential instrument transformers. The family of curves below describe the excitation characteristics for the 6005 multi ratio bushing current transformer shown on the previous sheet. Current transformer basics and the current transformer. Figure 144 shows the magnetic field during one cycle. In part 2, were going to talk about polarity marks. The current transformer function is different than that of a voltage transformer. Current transformer, standard for steadystate performance. Its primary consists of one or more turns of thick wire in the series with the line. British method here 5a is rated secondary current and 2volt across secondary. Ring core cts are available for measuring currents from 50 to 5000 amps, with windows power conductor opening size from 1 to 8.
Theyll give your presentations a professional, memorable appearance the kind of sophisticated look that. Dec 18, 2017 a current transformer ct is a type of transformer that is used to measure ac current. With this argument, can i short the the secondary sides of current transformer and voltage transformer together on a busbar and then ground this busbar to create a single grounding point. In its application to a current transformer, it is the number representing the amount by which the primary load current may be increased over its nameplate rating without exceeding the allowable temperature rise. The electrical current flowing in a transformer is al ternating current. In part three, well talk about current transformer ratio and how to relate primary current to secondary current. You can also use our live chat tool to speak directly with a sales representative. Current transformer or ct is a type of instrument transformer that is used in power system for measurement, detection, and protection the system. Ct s to be oversized so the total secondary current does not exceed the 5 amp rating, which reduces accuracy. A 1005 ratio ct, for example, has 20 turns whereas a 1001 ratio ct has 100 turns.
Accuracy decreases with increased burden load or low line. We know that, in a ct the primary current is dependent on the load current or line current as ct is connected in series with the line. Ppt transformer protection powerpoint presentation free. There is several documents say that for threephase instrument transformers ct,pt, there should be only one grounding point. Current transformer ratings 1 rated burden value of burden upon which accuracy claims are based usually expressed in va preferred values.
Apr 27, 2017 difference between ct and pt, current transformer and potential transformer april 27, 2017 may 27, 2018 admin 0 comments in this article we will know about what is difference between ct and pt. Current transformer circuits for power electronics. This is connected in series with the line carrying high current. These curves illustrate how high the secondary voltage will in rise in order to force the rated secondary current. Transformers used for voltage potential measurement steps down the voltage to the level of voltmeter. Ct burden can be expressed in two terms as example. The transformation ratio of the current transformer is always remained high, whereas for the potential transformer its remains low. The current transformer is a stepup transformer which is used to steps down the current to a known ratio. A test set operator connects the leads, pushes the buttons, and records the. Calculation of cts if the current transformer has primary to secondary current ratio of 100.
In some, the bar carrying high current may act as a primary. Shunt failure to remove the safety shunt will not keep the ct from operating but it will reduce the readings by 5080%. It would transform the current and bring down the voltage to a safer a management level so we can use our multimeter. The primary winding can consist merely of the primary current conductor passing once through an aperture in the current transformer core window or bartype, or it may consist of two or more turns wound on the core together with the secondary winding. Used in ac system for the measurement of current, voltage, power and energy. In part five we connected three tcs in delta and showed how the currents would circulate for the delta connection.
Sel transformer differential winding compensation settings. In part 1, we introduced the current transformer and we gave an example where we would want to use a ct. A ct is a current transformer and pt is a potential transformer. Okay, lets first begin by drawing an ideal transformer. Structure of transformer the transformer two inductive coils,these are electrical separated but linked through a common magnetic current circuit these two coils have a high mutual induction one of the two coils is connected of alternating voltage. The primary winding may be just a conductor or a bus bar placed in a hollow core. In part six were going to draw the current transformer model and show the voltages currents and impedances that are associated with the ct model. Download transformer powerpoint presentation jugaruinfo. Oct 24, 2016 the current transformer is a stepup transformer which is used to steps down the current to a known ratio. For pricing and availability of a specific ct model, give us a call at 614 8896152 or use the quote request form. Current transformers ct are used in high voltage hv and medium voltage mv 1 installations to give an image of electrical current to protection relays and units and metering equipment and they are designed to provide a current in its secondary proportional to the current flowing in its primary. Sf 6 110 kv current transformer tgfm series, russia current transformers ct are a series connected type of instrument transformer. One of its functions is as an ammeter to measure current flow amps.
The normal range of the current transformer for measuring the current is 5a or 1a whereas the standard voltage at the secondary winding of the potential transformer is up to 110v. A read is counted each time someone views a publication summary such as the title, abstract, and list of authors, clicks on a figure, or views or downloads the fulltext. These transformers step down the current to be measured, so that it can be measured with a normal range ammeter. The classification of protection current transformers follows the following. Download transformer powerpoint presentation get here complete powerpoint presentation on transformer and much more with download link. As the number of turns goes up, the secondary current is reduced by a proportional amount. They are high accuracy and ul certified current transformers, and many of them are made in usa. Instrument transformer basic technical information and. This is a plot of the ct secondary current against secondary voltage. The primary winding is so connected that the current to be measured passes through it and the secondary is connected to the ammeter. Its the main purpose is to stepupstepdown the current from higher power transmission line. Chart and diagram slides for powerpoint beautifully designed chart and diagram s for powerpoint with visually stunning graphics and animation effects. The current flows first in one direc tion, stops, then reverses and flows in the other direc274 unit 74 transformers tion. Winner of the standing ovation award for best powerpoint templates from presentations magazine.
Back to the basics current testing valence electrical. The correct way to specify and install current transformers. Nov 15, 2019 the basic principle of the current transformer is the same as that of the power transformer. Difference between ct and pt the electrical portal. Ct burden is an impedance of secondary circuit expressed in ohms and power factor. Current transformers are generally used to measure currents of high magnitude. Calculation of ct s if the current transformer has primary to secondary current ratio of 100. In a ct, the number of turns of the secondary winding and the current in the secondary winding are inversely proportional.
Kele offers full range of current transformers from 0. Click the appropriate winding connections, ct connections, phase rotation, and reference winding settings. Our new crystalgraphics chart and diagram slides for powerpoint is a collection of over impressively designed datadriven chart and editable diagram s guaranteed to impress any audience. Ct burden, knee point voltage, core saturation details of. Installation of current transformers janitza electronics.
The secondary consists of a large number of turns of fine wire and provides for the measuring instruments and relays a current which is a constant. Lets begin by drawing a delta connected transformer like such. Both current transformers have a transformer ratio of 1,0005a. Cts are the devices which helps in measuring large amounts currents in the line through measuring devices like ammeters etc. Ct accuracy a ct is most accurate at rated current with a low burden load. Rating factor rf is a term, which applies to a current transformer. Oct 08, 2016 calculation of cts if the current transformer has primary to secondary current ratio of 100. Since this method requires ideal conditions, it is generally better to use a summing transformer. Current transformers reduce high voltage currents to a much lower value and provide a convenient way of safely monitoring the. Heres a summary of the current transformer testing paper. There are four typical types of current transformers. Because you cant directly read the current, you need a current transformer to read and measure the current for you. Current transformer white paper the basics of current transformers ratio the ct ratio is the ratio of primary current input to secondary current output at full load.
What is the working principle of a current transformer. Course of ctflux during offset shortcircuit current. A typical connection diagram of a current transformer is shown in figure below. This power factor is not the power factor of secondary load. Chapter 16 current transformer design university of north. Ct s are instrument transformers used for converting primary current into a reduced secondary current for use with meters, relays, control equipment and other instruments the importance of instrument transformer tests is often underestimated. Scribd is the worlds largest social reading and publishing site. Instrument transformers are special types of transformers intended to measure cur rents and voltages.
A current transformer ct basically has a primary coil of one or more turns of heavy crosssectional area. A current transformer is an instrument transformer, used along with measuring or protective devices, in which the secondary current is proportional to the primary current under normal conditions of operation and differs from it by an angle that is approximately zero. Any meter that gets installed will require you to connect directly to voltage and current. Download transformer powerpoint presentation complete guide.
Current transformer is used to step down the current of power system to a lower level to make it feasible to be measured by small rating ammeter i. The primary winding can consist merely of the primary current conductor passing once through an aperture in the current transformer core window or bartype, or it may consist of two or more turns wound on the core together with the secondary winding wound type. A current transformer has only one or very few number of primary turns. A current transformer operates with a set primary current and will try to output a constant current to the load, independent of the load. Difference between ct and pt, current transformer and. Back to the basics current transformer ct testing as test equipment becomes more sophisticated with better features and accuracy, we risk turning our field personnel into test set operators instead of skilled field service technicians. Ppt instrument transformer powerpoint presentation. I wrote an article for the neta world magazine in 2004 that covers several different manual techniques for current transformer testing that should help even the most experienced technicians. Ensure the ct is connected to system properly in all respect primary and secondary.
Errors with current transformers cts require a lot of care to insure accurate metering. Current transformer circuit symbols according to ieee and iec standards. Here we will cover six important aspects of using instrument transformer in the power system. Why the secondary winding of current transformer is always. The magnetic field around the winding is constantly in motion. Worlds best powerpoint templates crystalgraphics offers more powerpoint templates than anyone else in the world, with over 4 million to choose from. Wiring faulty or improper wiring reduces accuracy by increasing burden.
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