Skip to main content

Current Transformer - Construction, Phasor and Errors


Current transformer are widely used for measuring the high current. The Current transformer steps down high value of current to low value which measuring instrument can read. If 2000 Amperes current to be read by a meter, it is not possible to read because a amall shunt resistance of high power rating in parallel to the galvanometer is required to be used. However, it is impractical to use a small value shunt resistance of high power rating to read high current directly by meter. That is why current transformer is used to lower the magnitude of the current so that measuring instrument and protective relay can read the current.

Construction of Current Transformer(CT)

The current transformer has two winding called primary and secondary. The primary winding has fewer number of turns and it is connected in series with primary circuit. The whole circuit current passes through the primary winding and it is desirable that the voltage drop across primary winding must be as low as possible. The current transformer has fewer turns of large cross section and, thus the voltage drop in the primary winding gets reduced up to a great extent.



The seconadry winding has more number of turns compared to the primary winding and it is connected with ampere meter, energy meter, watt meter,transducer and protection relay. The secondary winding of the CT must be connected with low impedance meter to keep the magnetic flux in the core up to its rated flux capacity. The flux in the core above the rated  capacity cause saturation of the magnetic core which leads to complete failure of current transformer. The CT secondary must not be left open because in this condition, the flux in the core increases manyfold and it cause CT core  saturation.


Based on the construction, there are two types of current transformer- Live Tank CT and Dead Tank CT. In both types of CTs, the core and windings are enclosed in a porcelain structure and this  structure is filled with mineral insulated oil which acts as cooling media, and it also provide required electrical insulation.

Symbol of Current Transformer(CT)

The terminal P1 and P2  shows the primary winding  of the CT and terminal S1 and S2 shows secondary winding of the CT. The CT ratio 2000/1 means the secondary current will be 1 ampere if primary current through the CT is 2000 amperes.

Equivalent Circuit  of Current Transformer(CT)

The CT equivalent circuit is as given below.



The primary of CT has few turns and it has very less resistance. The primary winding resistance and reactance is  denoted by Rp and Xp respectively. The secondary winding resistance and reactance is denoted by Rs and Xs respectively. The magnetisization components of the current transformer are Rc and Xm. Rc is  responsile for the core loss component, and Xm is the  magnetization reactance of CT. The other CT parameters  are as given below.

Phasor Diagram  of Current Transformer(CT)



The equivent circuit of the current transformer is similar to that of power tranformer and induction motor. From the phasor diagram  the transformer ratio and phase angle can be calculated.


CT Transformation Ratio

CT transformation ratio is calculated as follows.For finding transformation ratio we need to calculate primary current Ip as per definition and then divide it by secondary current Is. Let us consider the part of phasor of our importance for calculating Ip as shown below.

From the above phasor, the primary current Ip is phasor sum of nIs and I0The CT primary current Ip can be calculated using vector addition formula.


The magnetizing current Io is very small compared to the primary current Ip. Therfore, the above expression can be simplified as follows.



















From above expression, it is clear that transformation ratio is not equal to turn ratio. The transformation ratio and turn ratio will be equal if α=0 and δ=0.This condition can be  achieved if the core loss is equal to zero and the burden is purely resistive. This is an ideal condition, however this condition is practically impossible.

Phase Angle of Current Transformer

Phase angle of current transformer is defined as the angle between the primary current Ip and secondary current Is.  In above phasor diagram, θ is the phase angle.


Consider right angle triangle obc in the above phasor diagram.




Ratio Error of Current Transformer


The CT ratio Error is defined as the per unit deviation in transformation ratio from its nominal ratio. Ratio error is expressed in percentage.
Since the burden of the CT is generally resistive, therfore the power factor of the burden is unity and hence δ=0
Phase Angle Error of Current Transformer
The phase angle between primary and secondary of the current transformer must be 180 degree.The primary and secondary current must be out of phase. The deviation in the phase angle of the primary and secondary current is called the phase angle error. The phase angle between primary and seconadry current of the CT is denoted by angle θ.
Since the burden of the CT is generally resistive therfore the power factor of the burden is unity and hence δ=0. The phase angle error of CT is given by following expression.










Since the burden of the CT is generally resistive therfore the power factor of the burden is unity and hence δ=0.



















































http://news.chivindo.com/309/current-transformer---construction-phasor-and-errors.html

Comments

  1. Current Transformer - Construction, Phasor And Errors >>>>> Download Now

    >>>>> Download Full

    Current Transformer - Construction, Phasor And Errors >>>>> Download LINK

    >>>>> Download Now

    Current Transformer - Construction, Phasor And Errors >>>>> Download Full

    >>>>> Download LINK Qn

    ReplyDelete

Post a Comment

Popular posts from this blog

BT-BASIC commands used

8.10     Some of the most frequently used BT-BASIC commands used are: msi                               Changes default working directory. Mass storage is            Same as “msi” cat                               Catalogs (list)the node names in the specified directory.             get                               Brings the contents of a file into the system workspace.             load                             Same as “get”.             msi$                            Returns the directory pathname of the current working directory.             msi “..”                       Backs up one directory level.             findn                            Locates the next occurrence of the a given sting in the workspace. 8.11           If you wish to invoke the HP Board Graphics Viewer, type board graphics at the BT-BASIC command line and press the “ENTER” key on the keyboard. 8.12           A HP Board Graphics Viewer window should now appear

Perhitungan & Cara Merubah Kumparan Blender Dari 220 V Menjadi 12 V

          Seperti yang telah dijelaskan pada buku “menggulung motor listrik arus bolak-balik, servis peralatan listrik rumah tangga kelompok penggerak dan perbaikan peralatan listrik pertukangan”, bahwa motor penggerak yang digunakan pada perlatan listrik rumah tangga dan pertukangan seperti blender, mixer, bor tembak, gerinda dsb menggunakan jenis motor universal. Motor universal adalah jenis motor listrik yang dapat disuplai dengan sumber listrik arus bolak-balik (AC) dan arus searah (DC). Jadi peralatan-peralatan listrik rumah tangga dan pertukangan tersebut yang biasanya kita suplai dengan sumber listrik AC dari PLN atau Genset sebesar 220 V sebenarnya dapat juga kita suplai dengan sumber listrik DC yang tentunya tegangan juga harus sama yakni 220 V.           Yang menjadi permasalahan bagaimana kalau peralatan listrik rumah tangga atau pertukangan tersebut, sebagai contoh misalkan blender yang ingin digunakan atau dioperasikan pada tempat yang tidak terdapat sumber listrik PLN ata

BT-BASIC command line

8.8       At the BT-BASIC command line type the command  msi  and the directory path, then press the “ENTER” key on the keyboard.  Example:                   msi ‘/hp3070/boards/aspect/main’ 8.9       At the BT-BASIC command line type the command  get ‘testplan’ and press the   ENTER” key on the keyboard.  You should now see the body of the testplan file displayed in the work space of the BT-BASIC window. 8.10     Some of the most frequently used BT-BASIC commands used are:

Autodesk SketchBook Pro 2021 Full Version

BAGAS31 – Sesuai dengan namanya, Autodesk SketchBook Pro 2021 Full Version ini merupakan software digital sketching atau drawing terbaik yang bisa kamu gunakan. Pada versi terbaru kali ini, ada beberapa penambahan fitur yang sangat efektif. Dengan fitur baru tersebut, diharapkan mampu meningkatkan proses sketching maupun drawing kamu. Autodesk SketchBook sendiri sudah bisa kamu dapatkan secara gratis melalui website resminya. Namun untuk kamu yang mau download versi Autodesk Sketchbook Pro, maka bisa langsung download melalui link yang sudah saya sediakan di bawah ini. Download Autodesk SketchBook Pro 2021 Full Version Screenshot: System Requirements: Windows 10 2.5 – 2.9 GHz of Intel or AMD CPU 4 GB of Memory 256 MB Graphics card with OpenGL 2.0 support We recommend that you use a pressure-sensitive tablet and pen for basic features Download: Autodesk SketchBook Pro 2021 Full Version [ FileUp ][ Uptobox ][ UsersDrive ] Jamu Only [ FileUp ][ Uptob

Testhead

4.3         Testhead The testhead is that portion of the tester that supports the PIN, ASRU and Controller cards.   The testhead is divided into two BANKS and each BANK is divided into two MODULES, see figure 2 below.  Bank 1 contains modules 0 and 1, bank 2 contains modules 2 and 3.  The test fixtures are placed on the banks of the tester and locked down for board testing.  The testhead cards interface to the test fixture through the spring loaded pogo pin “nails” at the top edge on each of these card types. 4.4       Support Bay The support bay is a stand-alone cabinet that houses the power supplies for the Unit Under Test.  This bay also houses the test station power distribution unit and test station controller on earlier models. 4.5       Emergency Shutdown Switch The emergency shutdown switch is the large red button located at the lower left corner on the front of the testhead.  It turns off all AC power to the testhead, and is equivalent to turning off the m

Kelebihan dan Kekurangan Saluran Listrik Jenis Saluran Udara dan Saluran Bawah Tanah

Berdasarkan pemasangannya,   saluran distribusi dibagi menjadi dua kategori, yaitu : saluran udara (overhead line) merupakan sistem penyaluran tenaga listrik melalui kawat penghantar yang ditompang pada tiang listrik. Sedangkan saluran bawah tanah (underground cable) merupakan sistem penyaluran tenaga listrik melalui kabel-kabel yang ditanamkan di dalam tanah. 1.    Saluran Bawah Tanah (Underground Lines) Saluran distribusi yang menyalurkan energi listrik melalui kabel yang ditanam didalam tanah. Kategori saluran distribusi seperti ini adalah yang favorite untuk pemasangan di dalam kota, karena berada didalam tanah, maka tidak mengganggu keindahan kota dan juga tidak mudah terjadi gangguan akibat kondisi cuaca atau kondisi alam. Namun juga memilik kekurangan, yaitu mahalnya biaya investasi dan sulitnya menentukan titik gangguan dan perbaikannya. Kedua cara penyaluran memiliki keuntungan dan kerugian masing-masing. Keuntungan yang dapat diperoleh dari suatu jaringan bawah tanah adalah