The basics of current transformers nk technologies. Transformer operates when both circuits take effect of mutual induction. Types of transformer different types of transformer. Debaprasad kastha, department of electrical engineering, iit kharagpur. Temco has experience manufacturing and selling quality electrical products since 1968. Module 7 transformer version 2 ee iit, kharagpur lesson 23 ideal transformer version 2. Instrument transformer is an electrical device of high accuracy that is used to transform or isolate current or voltage levels. Constructional features of three phase transformers three phase connection of transformers dd0, dd6, yy0, yy6, dy1, dy11, yd1, yd11, zigzag, scott connection, open delta connection, three phase to six phase connection, oscillating neutral, tertiary. Power transformers are used to transfer large amount of power form 1 voltage level to other voltage level for obvious reasons and are used at p. Transformer only stepup or stepdown the level of ac voltage or ac current. In a power system, the currents and voltages are very large.
The primary purpose of this guide is to give the reader a basic understanding of how to apply instrument transformers in a practical way while observing good engineering practice. Such specially constructed transformers with accurate turns ratio are called as instrument transformers. Transformers used for voltage potential measurement. It might appear that the extension of range could be conveniently done by the use of shunts for currents and multiplier for voltage measurement, as in dc. Umanand, principal research scientist, power electronics group, cedt, iisc bangalore for more detail. Tech in electrical engineering iase deemed university. It should have a very high instrument efficiency which is the ratio of the quantity being measured to the power utilized by the instrument at full scale. Such specially constructed transformers with accurate turns ratio are called as instrument. A current transformer is defined as as an instrument transformer in which the secondary current is substantially proportional to the primary current under normal conditions of operation and differs in phase from it by an angle which is approximately zero for an appropriate direction of the connections. General principle and performance equations of d arsonval galvanometers, vibration galvanometer and ballistic galvanometer. Instrument transformers will transmit the signal to the metering and protective relaying instrumentation, with the purpose of protection of important equipment. Types of instrument transformer instrument transformer has two type 1 current transformer 2potential transformer 5 6. Instrument transformer sale, instrument transformers on sale.
Module 7 transformer version 2 ee iit, kharagpur lesson 23 ideal transformer version 2 ee iit, kharagpur contents 23 ideal transformer. After such a transformation, the stator variables currents and angle are. Instrument transformer technologies voltage and current. How to download all of the lectures in pdf for a course in.
As a normal transformer, its ratio can be specified as, so if voltage ratio of pt is known and the voltmeter reading is known then the high voltage to be measured, can be determined. Transformer, construction, transformer cooling, parallel operation, transformer losses. Ppt instrument transformer powerpoint presentation free. Siemens will equip a 145kilovolt kv substation owned by e. Instrument transformers facilitate to keep the measuring instrument far away from the live high voltage and high current power systems. Instrument transformer in power system, the currents and voltages are very large therefore, their direct measurements are not possible. This transformer step down the voltage to a safe limit value which can be easily measured by the ordinary low voltage instrument like a voltmeter, wattmeter and watthour meters, etc. Losses and torque equation, losses and efficiency calculation in d. The paper deals in a general way with the whole field of instrument transformer work, and in a more extensive manner with certain developmets and views for which the authors are more particularly responsible. You can find them according to your branch and subject in the below link national mission on education through ict this was initiated by iit madras. Which reduces the electrical insulation requirement for measuring instruments and protective circuits and also assures the safety of operators. Transformer cant stepup or stepdown the level of dc voltage or dc current. Instrument transformers are special types of transformers intended to measure cur rents and voltages. In these cases, we use long secondary leads from secondary core of the instrument transformers to the remote measuring instruments.
Mar 27, 2017 overall working of both the transformers is same, they both differ only in application point of view. Potential and current transformers, ratio and phase angle errors, phasor diagram, methods of minimizing errors. It might appear that the extension of range could be conveniently done by the use of shunts for currents and multiplier for volta. Bh curve of magnetic materials, fluxlinkage vs current characteristic of magnetic circuits, linear. The potential transformer may be defined as an instrument transformer used for the transformation of voltage from a higher value to the lower value. Temco manufactures a variety of electrical power transformers. Cts 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.
The various types of transformer shown in the figure above are explained in detail below. It should have a high sensitivity which is the ratio of the magnitude of the output. The most common usage of instrument transformers is to operate instruments or metering from high voltage or high current circuits, safely isolating secondary control circuity from the high voltages or currents. Several measuring instruments can be connected through a single transformer to power.
Instrument transformers potential transformer, current transformers for high voltage and current measurement. Instrument transformers can be simplified with basic magnetic circuits. 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. Here we will cover six important aspects of using instrument transformer in the power system. E degree from jadavpur university, kolkata in 2009 followed by. What are the difference between power transformer and. A high magnitude through fault external fault fed by the transformer shakes and heats a transformer winding, and the longer the through fault lasts, the greater the risk of it.
Apr 01, 2008 lecture series on basic electrical technology by prof. Different solutions for nonconventional instrument transformers have been developed in the last decade and are now available for hv gas insulated switchgear. With these innovative products of the so called blue portfolio. Ge is an industry leader in the design and manufacturing of high, medium and low voltage instrument transformers. There are several classes of accuracy for instrument transformers defined by the ieee, csa, iec, and ansi standards. Temco transformer manufacturer sales standard and custom instrument transformers manufactured to spec.
Instrument transformers are used for measurement and protective application, together with equipment such as meters and relays. The transformers are specifically designed to be used with the electrical equipment which falls into a variety of devices known as instruments. Current, voltage and combined transformers, oilpaper or. Nov 26, 2017 instrument transformers potential transformer, current transformers for high voltage and current measurement. You can transform the voltage or current down with a transformer whose turns ratio is accurately known, then measuring the stepped down magnitude with a normal range instrument.
For current transformers, the value of the reactance x is determined in a special way so that it represents the leakage flux. The original magnitude can be determined by just multiplying the result with the transformation ratio. The voltage transformer is designed to connect in parallel with the line to transform the line voltage to 115 or 120 volts suitable for the meter or relay. Nov 15, 2017 you will find all pdfs and also as mp3 file for all video lectures which are in nptel.
The primary of this transformer consists of one or more turns of thick wire connected in series with the line. These are connected across or parallel to the line which is to be monitored. Lecture series on basic electrical technology by prof. Basic electrical engineering pdf free download bee notes pdf. View notes l23tbet ee nptel from ee 203 at iit kanpur. A measuring instrument should possess some of the following important characteristic features. Their role in electrical systems is of primary importance as they are a means of stepping down the current or voltage of a system to measurable values, such as 5a or 1a in the case of a current transformers or 110v or 100v in the case of a voltage. Typical output levels of instrument transformers are 15 amperes and 115120 volts for cts and vts, respectively. These transformers reduce the voltage and current from high value to the low value which can be measured by conventional instruments. Instrument transformers are also used with protective relays for protection of power system basic function of instrument transformers is to step down the ac system voltage and. This is step up transformer because when we step up, the voltage increases and current decrease. Instrument transformers are the most common and economic way to detect a disturbance.
Principle of operation of dc machines, types of dc generators. Focussed on continuous improvement in process, product and people ci3p we in instrument transformers limited listen to our customers needs and provide the most technically and commercially. Current transformer and potential transformer are instrument transformers. Mod01 lec20 lecture20potential and current transformers. Electrical4u is dedicated to the teaching and sharing of. Figure 2 depicts the most basic magnetic circuit of an ideal instrument transformer. It is not intended to make the reader an instrument transformer designer. Instrument transformers will operate successfully under many atmospheric. On sweden with sf 6 free highvoltage products by the middle of 2020.
Instrument transformers are high accuracy class electrical devices used to isolate or transform voltage or current levels. Arteche offers a wide range that covers all our customers needs. Instrument transformer technologies pty ltd is known and respected throughout southern africa, thanks to the continuous development of knowhow and technology, the highly trained staff and the efficient state of production and testing facilities. Principle of operation of dc motors, types of dc motors.
Current transformers,voltage transformers and instrument. Potential transformer pt definition the potential transformer may be defined as an instrument transformer used for the transformation of voltage from a higher value to the lower value. Instrument transformers convert the currents and voltages of the h. Hv instrument transformer market 2018 by manufacturers, regions, type and application, forecast to 2023 hv instrument transformer is designed to transform high current and high voltage levels down to low current and low voltage outputs in a known and accurate proportion specified by the product nameplate ratios. Thus, a reduced voltage is fed to primary of the transformer. Transformer basics electric machines single phase transformer three phase transformer transformer type instrument transformer transformer test transformer accessories transformer oil maintenance of transformers installation of transformers transformer protection. It might appear that the extension of range could be conveniently done by the use of shunts for currents and multiplier for voltage measurement, as in.
With more than 100 years of experience, ge offers a broad array of standard and high accuracy models for revenue metering and system protection applications. Therefore, their direct measurements are not possible. Current transformer ct is a stepup transformer which steps down the current to a known ratio. Instrument transformer usually, surface insulation materials made from pressboard and polyester film or pure polyester film are used for electrical insulation. View notes l23tbet eenptel from ee 203 at iit kanpur. Instrument transformer basic technical information and. The basic principle of operation and construction of this transformer is similar to the standard power transformer. A digital instrument has an output varying in discrete steps. Jun 01, 2015 potential transformer is a voltage stepdown transformer which reduces the voltage of a high voltage circuit to a lower level for the purpose of measurement. The ratio of an instrument transformer is the relationship of its primary rating to its secondary rating. The potential transformer is connected in parallel with the circuit.
Bs en 50482 instrument transformers threephase inductive voltage transformers having um up to 52 kv. A single instrument transformer can operate many numbers of instrument at a time. This type of transformer is categorized on the basis of a number of turns in the primary and secondary windings and the induced emf. Instrument transformers may also be used as an isolation transformer so that secondary quantities may be used in phase shifting without affecting other primary connected devices. To cut down the vt size and cost, a capacitance potential divider is used fig 8. It is an auto transformer now these are very simple thing. The portfolio of instrument transformers ranges from low voltage at 600 v. An electronic counter is an example of a digital instrument. Try our instrument transformer today which is high precision class electrical devices utilized to transform or isolate voltage or the current levels. The primary winding of the transformer is connected to the high voltage or high current circuit, and the meter or relay is connected to the secondary circuit. The flux flows through the core and induces a current on the secondary winding. The primary windings of the potential transformer are directly connected to the power circuit whose voltage is to be measured.
If the quantity is to be directly measured, then deflection methods are used. Basic electrical engineering pdf notes bee pdf notes. Nov 17, 2019 instrument transformers provide electrical isolation between high voltage power circuit and measuring instruments. Classification, absolute and secondary instruments, indicating instruments. The orders comprise six bays, including circuit breakers for 72. A baked varnish coating ensures optimum adhesion between the layers after assembly in the measuring transducer. Jan 31, 2015 types of instrument transformer instrument transformer has two type 1 current transformer 2potential transformer 5 6. The instrument transformers like voltage transformer and current transformer are used for connecting the electrical instruments to the measuring instruments. Instrument transformers limited is a leading uk manufacturer of current and voltage transformers with more than 40 years of experience in the industry. Analyse the single phase and three phase transformers circuits. Instrument transformers selection guide engineering360. Current transformers play an important role in the monitoring and protection of electrical power systems. Some instrument transformer can be set through a pc. Instrument transformers are used in ac system for measurement of electrical quantities i.
The specific performance characteristics of instrument transformers are easily determined from the equivalent circuit. Single phase transformer and applications of single phase transformer. Now if the 2 windings of the transformer are connected in series to form as auto transformer find the possible voltage ratio and. Figure 4 works well for most instrument transformers. If you have any questions regarding our instrument transformers, please contact us. For example, the potential transformer mentioned above having a rating of 480.