Sep 23, 2016 in this video we walk you through the simple steps for performing a transformer turns ratio test using the vanguard instruments atrt03 s2 threephase turns ratio tester. Turns ratio test results should not deviate more than onehalf percent from either the adjacent coils or the calculated ratio. Transformer turns ratio test sets come in a variety of styles and test connections, however all turns ratio testers have at least two high leads and two low leads. Absorption ratio dar the ratio of 60 seconds30 seconds less than 1 failed 1. High voltage winding to low voltage winding and ground. This application note is focusing on using transformer turn ratio measurements for diagnostic. Hence every electrical power transformer must undergo through vector group test of transformer at factory site for ensuring the customer specified vector group of transformer. Gdbd transformer turn s ratio tester is specially designed for threephase transformer in power system, especially for transformer of type z winding and other transformers whose zeroload current is relatively high. In a shelltype shell form transformer, the steel magnetic circuit core forms a shell surrounding the windings. If the two transformers are connected in parallel, then the polarity should be known for the proper connection of the transformer. The test connection arrangement is shown in figure 2 c. The ratio test ensures that the transformer windings have the proper turns to produce the voltages required. Ttr300, ttr30047 highvoltage equipment read this entire manual before operating equipment m valley forge corporate center 2621 van buren avenue norristown, pa 194032329 u.
The ratio of the transformers primary and secondary windings with respect to each other produces either a stepup voltage transformer or a stepdown voltage transformer with the ratio between the number of primary turns to the number of secondary turns being called the turns ratio or transformer ratio. Using this test correctly can help to identify tap changer performance, shorted turns, open windings, incorrect winding connections and other faults inside transformers. Polarity test of transformer polarity means the direction of the induced voltages in the primary and the secondary winding of the transformer. Routine tests and type tests of transformers electrical4u. Performing a transformer turns ratio test with the vanguard atrt. The transformer consists of two separate windings placed over. Pdf transformer is a static device which transforms a. In the next tutorial to do with transformer basics. The typical excitation current test data pattern for a threelegged core transformer is two similar current readings and one lower current reading. Instruction manual for threephase ttr transformer turn. The voltage ratio of a transformer is the ratio of the rms terminal voltage of a higher voltage winding to the rms terminal voltage of a lower voltage winding under specified conditions of load. How to perform a power transformer turns ratio test eep.
As the measurement is conducted at low flux density, this measurement is equivalent to the turns ratio of the transformer. Transformer voltage ratio and turns ratio test youtube. Introduction to transformer turns ratio testing testguy. C electrical power from one voltage to another voltage keeping the frequency same by. In the factory, the transformer ratio of each tap and the vector group are verified during production and acceptance testing. First, the tap changer of transformer is kept in the lowest position and lv terminals are kept open. Transformer turns ratio tester electrical power testing.
Complete tests 1 and 2 for each winding of a threephase transformer individually with the remaining windings kept open. Vector group test of power transformer electrical4u. In an ideal transformer there are no losses so no loss of power then p in p out. When testing a transformer for turns ratio, the connections are determined by matching parallel vectors. Working principle of a transformer the basic principle on which the transformer works is faradays law of electromagnetic induction or mutual induction between the two coils.
This thermal voltampere rating corresponds to the fullload rating of a power transformer. Transformer turns ratio tester, turns ratio range 0. Home products transformer testportable ct pt analyzer. The transformer turns ratio test, or ttr test, confirms that the transformer has the correct ratio of primary turns to secondary turns. Power transformer factory test using ieee standards waldemar ziomek cg power systems canada ieee training, houston, texas, oct. If the transformer is new, the resistance test also serves as a verification of the manufacturers work. So transformer ration test is an essential type test of transformer. The megger mwa300 and 330a transformer winding analysers are here to offer you a faster, more efficient testing device through combining ttr and resistance testing in a single unit. Determine the turns ratio between the primary and secondary windings. If not available, input and output voltages can be measured. In this video we walk you through the simple steps for performing a transformer turns ratio test using the vanguard instruments atrt03 s2. May 10, 20 so transformer ratio test is an essential type test of transformer. The primary current of minimum of 25% rated primary current to be injected on primary side of ct with secondaries shorted and the secondary current can be measured and recorded for all cores. Turnsratio test results should not deviate more than onehalf percent from either the adjacent coils or the calculated ratio.
Cts provide isolation from the high voltage primary, permit. Power transformer turns ratio test is an ac low voltage test which determines the ratio of the high voltage winding to all other windings at noload. The ct ratio is the most important piece of information regarding the ct and must be recorded from the nameplate or the design criteria. Current transformers cts are instrument transformers that are used to supply a reduced value of current to me ters, protective relays, and other instruments.
If the pt has multiple taps different possible ratio combinations, all taps should be recorded for future reference in case a new pt ratio is required for the application. Ratio testing with applied burden is the most accurate and complete approach for testing at ct in service. The recommended ratio for the test voltage steps is 1 to 5. Transformer turns ratio test top electrical engineers. 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. The circuit connection shall be made as shown figure 4. This test ensures that the transformer will provide the proper stepup or step down in voltage. The transformer winding voltage ratio is directly proportional to the winding turns ratio. At each step, test voltage should be applied for the. Transformers are subject to several stresses and changes in their operational life, and so utilities and service companies schedule different transformer testing programs to assess their condition throughout the life of the transformer.
Power transformer testing measuring ratio and magnetization. Understanding insulation resistance testing pdf 0712 technical assistance 800 34391. A transformer is a device used to change the voltage levels of electricity to facilitate the transfer of electricity from generating stations to. The ratio determines the pt operating characteristics. Extreme caution must be observed when testenergizing highratio transformers 10 to 1, for example, because high voltages will be present at the transformer. There are two types of polarity one is additive, and another is subtractive. The test equipment used is ordinarily a turns ratio tester designed for the purpose. Electrical test equipment application solutions from megger. This test is similar to tests 1 and 2, but as applied to a three phase transformer for phase identification and phase continuity check.
Ct ratio with burden testing secondary connection is made through the test switch same connection that is used for the rest of the site testing. Gerald sellers lab manager shermco oil analysis laboratory. The instruments, when operated as described in the user manual, provide convenient and accurate readings of ratio and phase deviation of power transformers. A transformer turns ratio test set such as the threephase automatic ttr can directly measure the ratio of most types of transformers. True threephase transformer turns ratio tester trt63 test voltages from 1 to 250 v ac turns ratio range 0,8 50 000 the best turns ratio accuracy of 0,03% singlephase test voltage true threephase test voltage automatic vector group detection builtin tap changer control unit. Transformer ratio can change due to several factors, including physical damage from faults, deteriorated insulation, contamination and shipping damage. The transformer consists of two separate windings placed over the laminated silicon steel core.
Power transformer factory test using ieee standards. The ttr300 series of threephase transformer turns ratio test sets are designed to measure the turns ratio of power, instrument, and distribution transformers in a substation or manufacturing environment. The turnsratio test is used to determine the number of turns in one winding of a transformer in relation to the number of turns in the other. The atrm200 excites the high voltage winding of the test transformer with a signal of 36v, line frequency. Portable ct pt analyzertransformer testgfuve electronics. Voltage and turn ratio test of transformer electrical4u. The primary current of minimum of 25% rated primary current to be injected on primary side of ct with secondaries shorted and the secondary current can be measured and recorded for all cores limits. Basics, maintenance, and diagnostics vii contents continued page 4. Gdbd transformer turns ratio testerturns ratio tester. Turns ratio tests optional test this test is to ensure the turns ratio of ct at all taps.
Transformer turns ratio test sets come in a variety of styles and test connections, however all turns ratio testers have at. The pt ratio is the most important piece of information and must be recorded from the nameplate or the design criteria. The ratio determines the ct operating characteristics and is used as reference for. True threephase transformer turns ratio tester trt63. Transformer turn ratio may also be measured with a hv tan delta test set such as the megger delta20003000. Instrument transformer theory and testing steve hudson, pe. The transformer turns ratio test helps to identify problems such as shortedturns or openturns, incorrect connections, tap changer and internal magnetic core problems, etc. Installation measurements should be filed for future reference 2. The ratio and phaseangle inaccuracies of any standard asa accuracy class1 of potential transformer are so small that they may be neglected for protectiverelaying purposes if the burden is within the thermal voltampere rating of the transformer. Choosing the correct turns ratio test in order to determine which type of turns ratio test is most appropriate for a particular transformer, a number of issues should be considered.
Jun 28, 2012 in the factory, the transformer ratio of each tap and the vector group are verified during production and acceptance testing. The voltage should be applied only in the high voltage winding in order to avoid unsafe voltage. Besides measuring turns ratio, atrm200 also measures phase angle deviation between the tested windings. Ttr300 series threephase transformer turns ratio test set. Because a test confirms what you know, if you can apply in real life what you have learned in a classroom, under strict, rigorous and controlled conditions. What kind of problems will the resistance test detect.
This is not a commonly used test step voltage test method in this test, the operator applies two or more test voltages in steps. Transformers objectives after studying this unit, the student will be able to state the purpose of a transformer. Measuring transformer ratio from one external terminal to another can reveal a great deal of. In this video we walk you through the simple steps for performing a transformer turns ratio test using the vanguard instruments atrt03 s2 threephase turns ratio tester. The gf106t ct analyzer is mainly used for field testing of p class ct and pt.
Jun 26, 2016 transformer turns ratio test connections. Performing a transformer turns ratio test with the vanguard. The turns ratio is equivalent to the voltage ratio of potential transformers and can be expressed as follows. The turns ratio test is performed on all taps of every winding. In order to determine which type of turns ratio test is most appropriate for a particular transformer, a number of issues should be considered. Mar 10, 2020 transformer ratio test the performance of a transformer largely depends upon perfection of specific turns or voltage ratio of transformer.
Ratio test no load loss and current test sound level test induced voltage test 12 measurement of no load loss and current. Example of single phase, handcranked ttr transformer turns ratio test set measures the turns ratio and exciting current of windings in. The transformer turns ratio tester ttr is device used to measure the turns ratio between the windings example shown below. So for ensuring proper performance of electrical power transformer, voltage and turn ratio test of transformer one of the important tests. This advanced 3phase transformer test system provides complete ratio, phase and winding resistance measurements with only one 3phase leadset connection.
Vector group test of transformerthe vector group of transformer is an essential property for successful parallel operation of transformers. The transformer turns ratio test is used to make sure that the ratio between the windings of the primary and secondary coils follow the proper specifications. The performance of a transformer largely depends upon perfection of specific turns or voltage ratio of transformer. Transformer turns ratio test set threephase ttr transformer. As a perfect transformer should show no phase difference. On window type units with low primary current ratings, where the primary conductor size is small, the ratio of the transformer can be changed by taking multiple wraps of the primary conductor through the window. Testing of power transformers seems like a similar experience. The test items mainly include excitation characteristic, polarity, phase and ratio error. The transformer ratio test is used as both an acceptance test and a maintenance test, while the polarity test is primarily an acceptance test.
This test also performed as a routine test of transformer. As mentioned before, the types of transformer testing we will show in this article a very important test of the transformer testing. Performing a transformer turns ratio test with the. Ratio, phase angle deviation, percent deviation, excitation current. In order to test that a transformer will meet its design specification, a number of functions should be tested and one of the most commonly used tests is turns ratio. The table below shows each test with a description, the related specifications and a summary of the benefit provided by that test. Regardless of the configuration, star, delta or zigzag, the measurements are normally made phase to phase and comparisons are made to the estimated ratios defined by the transformer template voltages and configuration. For all practical purposes, when the transformer is on open circuit, its voltage and turns ratios may be considered equal.
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