Potential transformers used primarily in a step down environment to monitor voltage. A ct has large number of turns on its secondary winding, but very few turns on its primary winding. A current transformer ct is another special instrument transformer designed to step down the current through a power line to a safe level for an ammeter to measure. The portfolio of instrument transformers ranges from low voltage at 600 v. Supply authorities are under obligation to their customers to maintain the supply voltage between certain limits. Components of each of these transformer categories are defined and the potential problems and remedial actions are discussed. Instrument transformers convert signal levels from dangerous high voltage or inconvenient high current, or current at high voltage to levels appropriate for metering. A varying current in any one coil of the transformer produces a varying magnetic flux in the transformers core, which induces a varying electromotive force across any other coils wound around the same core. To start with, both are instrument transformers basically used for measurement and protection purpose in power systems. Compared to the conventional transformer, potential transformers or pts use larger conductor sizes and core. Manufactured using highgrade material like copper, transformer oil, creep tape, insulators, toroidal corelaminationcork sheet kraft paper and steel components. A potential transformer or voltage transformer is a special kind of transformer used to measure voltages higher than you would want to measure directly. Table 1 standard burdens for potential transformers burden voltamps at 120v burden power factor w 12. Download electric power transformer engineering pdf book free online from electric power transformer engineering pdf.
Mar 11, 2017 a potential transformer or voltage transformer is a special kind of transformer used to measure voltages higher than you would want to measure directly. It is based on the principle of mutual induction, a transformer is an ac device it cannot work on dc a transformer can only change the ac currentvoltage. Electric power transformer engineering, third edition expounds the latest information and developments to engineers who are familiar with basic principles and applications, perhaps including a handson working knowledge of power transformers. Ieee standard terminology for power and distribution.
Amp rating indicating diameter inches mm length inches mm ferrule length inches mm max voltage max ir rms sym spare parts clips spare parts live parts. Transformer maintenance a pdh online course for engineers. Apr 24, 2016 current transformers ct and potential transformers pt are used to measure the current and voltage in a circuit of the order of hundreds of amperes and volts respectively. Manufactured using highgrade material like copper, transformer oil, creep tape, insulators, toroidal corelaminationcork. This is step up transformer because when we step up, the voltage increases and current decrease. Special transformers and applications transformers. Section 19 distribution drytype transformers low voltage. Potential transformers these potential transformers are used in power metering applications and allow you to monitor electrical power systems.
Transformers used for voltage potential measurement steps down the voltage to the level of voltmeter. Instrument transformer theory and testing steve hudson, pe engineering manager 10737 lexington drive knoxville, tn 37932 phone. This research paper deals with the simulation of 2 kv. Using potential transformers continental control systems. Single phase low voltage potential transformers flexcore.
There are several different winding on the primary of the potential transformer but in current transformer, there is only a single winding. For example, the potential transformer mentioned above having a rating of 480. A tap changer is a device fitted to power transformers for regulation of the output voltage to required levels. Load flow analysis of 2 kv substation using etap software rohit kapahi abstractpower is essentially required for the development of any country. The terminal of the transformer should be designed so that the variation of the voltage ratio with load is minimum and the phase shift between the input and output voltage is also minimum. This course has been developed from ansiieee standards, the evaluation of the existing facilities, and from surveys of the many existing power transformer which have been put into service in the last seventy years. The potential transformer is made with highquality core operating at low flux density so that the magnetising current is small. The theory of operation of a potential transformer is essentially same as that of the power transformer. Potential transformer free download as powerpoint presentation. Available from 25 kv to 800 kv for measurement, protection and control. Adding potential transformers has the effect of reducing the measured line voltage by the pt ratio lets say 35. The primary terminal of the potential transformer is connected to the line for measuring the line voltage. Cts current transformers pts potential transformers.
A potential transformer pt is a special instrument transformer designed to provide a precise voltage stepdown ratio for voltmeters measuring high power system voltages. In circuit where measurements of high voltage and high current is involved, they are used there. Design and practice, this greatly expanded second edition also emphasizes diagnostic. This video is developed for the benefit of my student of 2nd year ee. Key differences between current and potential transformer. A voltage transformer has 1500 turns of wire on its primary coil and 500 turns of wire for its secondary coil. Pdf transformer engineeringdesign and practice book. Working of potential transformer the electrical portal. Ieee standard terminology for power and distribution transformers. Instrument transformers will operate successfully under many atmospheric conditions and transients, and switching overvoltages. As the ratio moves from a larger number on the left to a smaller.
They are designed for connection linetoline or linetoneutral in the same manner as ordinary voltmeters. 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. The primary winding is connected directly to the power circuit either. Voltage transformer is necessary for directional, voltage, distance protection. 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. Instrument transformer basic technical information and. Lets say, for instance, that you have a 100kv grid and want to know how much powerenergy you. The primary winding is connected in series with the load so that it carries full load current. This is normally achieved by changing the ratios of the transformers on the system by altering the number of turns in one winding of the appropriate transformers.
It is basically the phasor diagram of potential transformer explanation for transformat. Types of instrument transformer instrument transformer has two type 1 current transformer 2potential transformer 5 6. Ge is an industry leader in the design and manufacturing of high, medium and low voltage instrument transformers. Potential transformer primary fuse basis for sizing prc electrical 2 may 12 00. Load flow analysis of 2 kv substation using etap software. Single, double, and triple, current characteristics designed to provide current limiting protection for power transformers, potential transformers, power centers, feeder centers, and unit sub stations. Potential transformer or voltage transformer gets used in electrical power system for stepping down the system voltage to a safe value which can be fed to low ratings meters and relays. Potential transformer testing ptvt valence electrical. Potential transformers pts pts step down high voltages to the voltage needed by the meter usually. Actually they are protective type voltage transformer. Commercially available relays and meters used for protection and metering, are designed for low voltage. The main difference between a potential transformer and a power transformer is that the load current of the potential transformer depends purely on the exciting current and its.
A varying current in any one coil of the transformer produces a varying magnetic flux in the transformer s core, which induces a varying electromotive force across any other coils wound around the same core. A potential transformer is a conventional transformer having primary and secondary windings. Potential transformer testing ptvt i cowrote an article for the neta world magazine in 20042005 that covers several different manual techniques for potential transformer testing that explains several lowtech solutions for potential transformer testing. Since the meter sees 120 vac, many of the measurements it reports will be low by a factor of 35 unless they are scaled up by 35. These potential transformers are used in power metering applications and allow you to monitor electrical power systems. Feb 21, 2018 this video is developed for the benefit of my student of 2nd year ee. In first sentence you are saying that interturn fault will not result in fuse operation. Potential transformers are used in high voltage voltmeters while current transformers are used in place of the ordinary ammeter. Potential transformer primary fuse basis for sizing. Basics, maintenance, and diagnostics vii contents continued page 4. Difference between current transformer and potential. 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.
Voltage transformer or potential transformer theory. The foreseen application of the voltage transformer is used to determine the rated secondary voltage, the accuracy power. The capacitor voltage transformer cvt uses a capacitance potential divider and is used at higher voltages due to a lower cost than an electromagnetic pt. Current transformers, inductive voltage transformers, capacitive voltage transformers, combined currentvoltage transformers and station service voltage transformers are 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. Instrument transformers will transmit the signal to the metering and protective relaying instrumentation, with the purpose of protection of important equipment. To maintain the generation of electric power at adequate level the power has to be transmitted in proper form and quality to the consumer.
The voltage transformer must be suited to requirements relating to protection and measuring devices. Current transformer and potential transformer manufacturer. Potential transformer voltage transformer is used for protection and measurement. An additional winding in a transformer that can be connected to a synchronous. 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. 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. Used in ac system for the measurement of current, voltage, power and energy. Current transformers ct and potential transformers pt are used to measure the current and voltage in a circuit of the order of hundreds of amperes and volts respectively. Stepping up is done to evacuate the generated power while stepping down is done for the consumer requirements.
A transformer is a stationary device which is used for stepping updown of voltage of alternating current. Building on the bestselling transformer engineering. What is a transformer tap changer engineering tutorial. What will be the turns ratio tr of the transformer. E series potential transformer secondaries e1, e2, e3, etc. The electromagnetic potential transformer is a wirewound transformer. Established in the year 1989, we, victrans engineers, are an eminent manufacturer and supplier of an unsurpassed assortment of current transformer 33 kv up to 220 kv and potential transformer 33 kv up to 145 kv. The potential transformer reduced the high value of voltage into the small value which can easily be measured by the voltmeter or meter. However, we are listed as an essential business and therefore, will continue to provide services during these trying times.
What are a potential transformer and a current transformer. Due to the covid19 outbreak, people in ohio have been ordered to shelter in place until april 6, 2020. View potential transformer ppts online, safely and virusfree. Difference between a potential transformer and current transformer. Electric power transformer engineering pdf download free. An optical voltage transformer exploits the faraday effect, rotating polarized light, in optical materials. A transformer is a passive electrical device that transfers electrical energy from one electrical circuit to another, or multiple circuits. 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. The ratio of an instrument transformer is the relationship of its primary rating to its secondary rating.
Instrument transformer in power system, the currents and voltages are very large therefore, their direct measurements are not possible. Next sentence it is said that fuse will operate in the event of a pt failure. Transformer rfq form to request a specific part to meet your requirements. This is a simplest form of potential transformer definition. Two types of voltage transformer are used for protectiverelaying purposes, as follows. Dec 30, 2018 potential transformer or voltage transformer gets used in electrical power system for stepping down the system voltage to a safe value which can be fed to low ratings meters and relays. Khaparde helps you design better transformers, apply advanced numerical field computations more effectively, and tackle operational and maintenance issues.
52 684 1221 528 504 484 289 962 739 789 596 341 1363 1375 1346 1011 907 1400 750 580 829 446 181 1426 857 1301 119 570 270 916 42 546 310 155 29 1462 770