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. The ct ratio is the most important piece of information regarding the ct and must be recorded from the nameplate or the design criteria. The transformer ratio test is used as both an acceptance test and a maintenance test, while the polarity test is primarily an acceptance test. As mentioned before, the types of transformer testing we will show in this article a very important test of the transformer testing. Transformer turns ratio tester electrical power testing. 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. Jun 28, 2012 in the factory, the transformer ratio of each tap and the vector group are verified during production and acceptance testing. So for ensuring proper performance of electrical power transformer, voltage and turn ratio test of transformer one of the important tests. The pt ratio is the most important piece of information and must be recorded from the nameplate or the design criteria. 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.
Instruction manual for threephase ttr transformer turn. In an ideal transformer there are no losses so no loss of power then p in p out. The efficiency of a transformer is the ratio of the power it delivers to the load to the power it absorbs from the supply. The performance of a transformer largely depends upon perfection of specific turns or voltage ratio 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 limits. 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. Voltage and turn ratio test of transformer electrical4u.
If the two transformers are connected in parallel, then the polarity should be known for the proper connection of the transformer. 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 test is conducted to prove that the ratio of the ct is as specified, and to verify the ratio is correct at different taps of a multi tap ct. 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.
Installation measurements should be filed for future reference 2. Introduction to transformer turns ratio testing testguy. 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. Understanding insulation resistance testing pdf 0712 technical assistance 800 34391. Absorption ratio dar the ratio of 60 seconds30 seconds less than 1 failed 1. As the measurement is conducted at low flux density, this measurement is equivalent to the turns ratio of the transformer. Transformer ratio can change due to several factors, including physical damage from faults, deteriorated insulation, contamination and shipping damage. Determine the turns ratio between the primary and secondary windings.
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. 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. The table below shows each test with a description, the related specifications and a summary of the benefit provided by that test. In this video we walk you through the simple steps for performing a transformer turns ratio test using the vanguard instruments atrt03 s2. The test equipment used is ordinarily a turns ratio tester designed for the purpose. Complete tests 1 and 2 for each winding of a threephase transformer individually with the remaining windings kept open.
In the next tutorial to do with transformer basics. Polarity test of transformer polarity means the direction of the induced voltages in the primary and the secondary winding of the transformer. Turnsratio test results should not deviate more than onehalf percent from either the adjacent coils or the calculated ratio. 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. Routine tests and type tests of transformers electrical4u. Cts provide isolation from the high voltage primary, permit.
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. 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. As a perfect transformer should show no phase difference. Transformer voltage ratio and turns ratio test youtube. The transformer turns ratio test, or ttr test, confirms that the transformer has the correct ratio of primary turns to secondary turns. This thermal voltampere rating corresponds to the fullload rating of a power transformer. Instrument transformer theory and testing steve hudson, pe. Transformer turns ratio test set threephase ttr transformer. 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 transformer winding voltage ratio is directly proportional to the winding turns ratio. Transformer turns ratio test sets come in a variety of styles and test connections, however all turns ratio testers have at.
The ratio test ensures that the transformer windings have the proper turns to produce the voltages required. Home products transformer testportable ct pt analyzer. This advanced 3phase transformer test system provides complete ratio, phase and winding resistance measurements with only one 3phase leadset connection. Turns ratio test results should not deviate more than onehalf percent from either the adjacent coils or the calculated ratio.
How to perform a power transformer turns ratio test eep. The recommended ratio for the test voltage steps is 1 to 5. This test also performed as a routine test of transformer. Using this test correctly can help to identify tap changer performance, shorted turns, open windings, incorrect winding connections and other faults inside transformers. The transformer turns ratio test helps to identify problems such as shortedturns or openturns, incorrect connections, tap changer and internal magnetic core problems, etc. 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. What kind of problems will the resistance test detect. At each step, test voltage should be applied for the. Turns ratio tests optional test this test is to ensure the turns ratio of ct at all taps.
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. Besides measuring turns ratio, atrm200 also measures phase angle deviation between the tested windings. In order to determine which type of turns ratio test is most appropriate for a particular transformer, a number of issues should be considered. Vector group test of power transformer electrical4u. Current transformers cts are instrument transformers that are used to supply a reduced value of current to me ters, protective relays, and other instruments. The transformer consists of two separate windings placed over. High voltage winding to low voltage winding and ground. 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. If not available, input and output voltages can be measured. Pdf transformer is a static device which transforms a.
Basics, maintenance, and diagnostics vii contents continued page 4. The instruments, when operated as described in the user manual, provide convenient and accurate readings of ratio and phase deviation of power transformers. 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. Transformer turns ratio tester, turns ratio range 0. Transformer turns ratio test top electrical engineers. This application note is focusing on using transformer turn ratio measurements for diagnostic. This is not a commonly used test step voltage test method in this test, the operator applies two or more test voltages in steps. This test is similar to tests 1 and 2, but as applied to a three phase transformer for phase identification and phase continuity check. Electrical test equipment application solutions from megger. So transformer ration test is an essential type test of transformer. First, the tap changer of transformer is kept in the lowest position and lv terminals are kept open.
A rugged and robust design makes these instruments well suited for use in a variety of harsh environments. The ratio determines the ct operating characteristics and is used as reference for. 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. 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 ratio determines the pt operating characteristics. 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. In the factory, the transformer ratio of each tap and the vector group are verified during production and acceptance testing. Gdbd transformer turns ratio testerturns ratio tester. Example of single phase, handcranked ttr transformer turns ratio test set measures the turns ratio and exciting current of windings in.
This test ensures that the transformer will provide the proper stepup or step down in voltage. The turns ratio is equivalent to the voltage ratio of potential transformers and can be expressed as follows. Transformer turn ratio may also be measured with a hv tan delta test set such as the megger delta20003000. Ratio testing with applied burden is the most accurate and complete approach for testing at ct in service. A transformer turns ratio test set such as the threephase automatic ttr can directly measure the ratio of most types of transformers.
The test items mainly include excitation characteristic, polarity, phase and ratio error. Measuring transformer ratio from one external terminal to another can reveal a great deal of. Portable ct pt analyzertransformer testgfuve electronics. Gerald sellers lab manager shermco oil analysis laboratory. True threephase transformer turns ratio tester trt63. If the transformer is new, the resistance test also serves as a verification of the manufacturers work. Performing a transformer turns ratio test with the vanguard atrt. Ratio, phase angle deviation, percent deviation, excitation current.
C electrical power from one voltage to another voltage keeping the frequency same by. The transformer turns ratio tester ttr is device used to measure the turns ratio between the windings example shown below. Vector group test of transformerthe vector group of transformer is an essential property for successful parallel operation of transformers. Transformers objectives after studying this unit, the student will be able to state the purpose of a transformer.
Performing a transformer turns ratio test with the vanguard. Ttr300 series threephase transformer turns ratio test set. May 10, 20 so transformer ratio test is an essential type test of transformer. The atrm200 excites the high voltage winding of the test transformer with a signal of 36v, line frequency. The transformer consists of two separate windings placed over the laminated silicon steel core. The voltage should be applied only in the high voltage winding in order to avoid unsafe voltage. 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.
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. 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. When testing a transformer for turns ratio, the connections are determined by matching parallel vectors. Ttr300, ttr30047 highvoltage equipment read this entire manual before operating equipment m valley forge corporate center 2621 van buren avenue norristown, pa 194032329 u. For all practical purposes, when the transformer is on open circuit, its voltage and turns ratios may be considered equal. The test connection arrangement is shown in figure 2 c. Power transformer factory test using ieee standards waldemar ziomek cg power systems canada ieee training, houston, texas, oct. Testing of power transformers seems like a similar experience. The turns ratio test is performed on all taps of every winding. The circuit connection shall be made as shown figure 4. Performing a transformer turns ratio test with the. Mar 10, 2020 transformer ratio test the performance of a transformer largely depends upon perfection of specific turns or voltage ratio of transformer. Power transformer factory test using ieee standards.
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