This test is very reliable for condition monitoring of physical condition of transformer windings. Hipot test is typically used for acceptance testing or after transformer repair testing. Sweep frequency response analysis test sfra test electrical4u. Oil diagnostic suites for transformer oil diagnostics. The objectives of this experiment are to find the approximate per phase equivalent circuit parameters of a 3. Etc provides this testing as a service to our customers to ensure compatibility between the ballastlamp or driver and our dimming system. Performance test of faulty distribution transformers along.
Magnetization and primary injection test of current. Field testing of a power transformer before putting into service 50mva. Transformer testing commissioning, routine, diagnostic. So for ensuring proper performance of electrical power transformer, voltage and turn ratio test of transformer one of the important tests. The following definitions are used in megger ttr test instruments. Sep 26, 2017 mainly two types of transformer testing are done at manufacturer premisestype test of transformer and routine test of transformer. Dismantling a power transformer to determine its condition is hardly ever a practical possibility. Nov 17, 2019 sweep frequency response analysis test or in short sfra test can detect efficiently, displacement of transformer core, deformation and displacement of winding, faulty core grounds, collapse of partial winding, broken or loosen clamp connections, short circuited turns, open winding conditions etc. It is also known as iovtinduced over voltage test, it is one of the routine test of transformers usually performed to check in turn insulations of the windings.
The procedure of the transformer ratio test is simple. In addition to the above transformer testing methods, the power transformer also goes through some other tests, performed on it, before the actual commissioning of the transformer at the site. The transformer has been built to standard damage has not been sustained during transit or installation. Megger provides thoughtfully equipped transformer test instruments for routine screening needs. Hence, it is essential to inspect and calibrate those instrument transformers at regular intervals. Iec6007618 sfra of power transformers, typical test. Sweep frequency response analyzer sfra quick start guide.
In addition to that some transformer tests are also carried out at the consumer site before commissioning and also periodically in regular and emergency basis through out its service life. Basics, maintenance, and diagnostics vii contents continued page 4. Connection on cpc100 will be same as the shown figure. From which side of a large transformer, would you like to carry out s. The test methods used by the authors for presenting the results are described. Type test and routine test of transformer electrical mastar. 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 is the correct procedure for dvdf and hv test on. The different tests conducted in a distribution transformer as per the standards are discussed below. Insulation power factor testing of power transformers.
The following sections of the ansineta standard for acceptance testing specifications for. Measurement of winding resistance iec 6007611 clause. The electrical field tests recommended for routinely testing a transformer include. For example, unless there is reason to be concerned about winding deformation, a leakage reactance test is probably not necessary. The power transformer of rating 10 kva, 1 v440 v, 3phase, 50 hz, dyn11 has been specially developed inhouse for carrying out sfra testing by. On distribution transformer this type of switch may also be used to change nameplate voltage andor configuration. Ltc because in order to change taps, the transformer has to be taken out of service or at least disconnected from the load.
The ac hv test value should not surpass 75% of the factory test value. May 10, 20 so transformer ratio test is an essential type test of transformer. Transformer nameplate voltage, tnv labelled linetoline voltage for a winding defined on transformer template. When ac hipot tests are used for routine maintenance, the power transformer can be examined at. Sfra testing on transformers electrical test equipment. Measure the voltage at the both primary and secondary termination at all the phases. A typical excitation current test data pattern for a threelegged core is two similar current readings and on lower current reading. Power failure or sudden power outage as a result of blown on the high voltage distribution fuses or consequent loss of a transformer cannot be overemphasized. Testing of three phase power transformer ijireeice. Testing power transformers highvoltage transformers are some of the most important and expensive pieces of equipment required for operating a power system.
Test connection w 1 synchronous generator 2 test transformer 3 current trans. This test also performed as a routine test of transformer. Sweep frequency response analysis test or in short sfra test can detect efficiently, displacement of transformer core, deformation and displacement of winding, faulty core grounds, collapse of partial winding, broken or loosen clamp connections, short circuited turns, open winding conditions etc. By using the latest proven sfra test techniques, it is possible to accurately assess transformer condition without dismantling it. Testing of power transformers seems like a similar experience. The power loss is also a very convenient number when checking the accuracy of measurements.
The purchase, preparation, assembly, operation and maintenance of transformers represent a large expense to the power system. Unlike the tests described previously, in the present case nominal voltage is applied. Figure 5 shows the result of the curve fitting for core 1, considering the y axis to be the current and x axis to be the voltage, the following expression give the standard. This study focuses on the temperature of transformer winding, voltage ratio across hvlv, asymmetrical flux distribution in the core, insulation resistance of paper. Interpretation of sweep frequency response analysis sfra. The above standard testing is offered in specific diagnostic suites designed to provide the maximum condition information on the transformers. Apply the formula or plot the values in the graph to get the vector group. Instrument transformers for metering purposes must have a high degree of accuracy up to class 0. Routine tests and type tests of transformers electrical4u. The standard test suites are designed for individual samples to deliver a routine set of oil analysis at low cost. Iec6007618 sfra of power transformers, typical test sequences this application note will discuss typical transformer configurations and measurement sequences as specified in the iec6007618 international standard. Ratings, voltage ratio, tapping range, impedance and other technical parameters may be selected as per cbip publication no.
Standard for acceptance testing specifications for electrical. Condition monitoring of power transformer by using sfra test. Repeat the test for the other phases and the other secondary cores. May 15, 2016 sfra stands for sweep frequency response analysis. Sfra testing on transformers dismantling a power transformer to determine its condition is hardly ever a practical possibility. Transformer sweep frequency response analysis sfra by g m kennedy, a j mcgrail and j a lapworth, doble engineering, sweep frequency response analysis sfra is one of the most powerful diagnostic tools for assessing mechanical damage to a transformer winding. The preference is that all large power transformers 1 mva be tested with ttr test set.
How to calculate efficiency of the transformer at a given load and power factor. The transformer shall conform in all respects to highest standards of engineering, design, workmanship, this specification and the latest revisions of relevant standards at the time of. The latest sfra test sets make these techniques more accessible, more convenient and more dependable that ever. According to 3 sfra method determines the transformer responses in a time or frequency area. Scribd is the worlds largest social reading and publishing site. Section 7 of the ansineta standard for acceptance testing specifications for electrical power equipment and systems may be reproduced and used on a cut and paste basis for the particular type of equipment to be tested. Feb 18, 2014 the value of the test voltage between phases and between phase and earth is measured at the lv side on an accurate voltage transformer. This guide is based on the operation of the n4l sfra45 sweep frequency response analyzer and will provide a. Sweep frequency response analysis sfra is a method to evaluate the mechanical integrity of core, windings and clamping structures within power transformers by measuring their electrical transfer functions over a wide frequency range. Magnetization and primary injection test of current transformer for protective relaying jacob tsado 8 current transformers.
To connect the ground reference cable and test leads and run sfra. Apply 3 phase supply voltage 415 v ac across the primary termination of the transformer. The latest sfra test sets make these techniques more accessible, more convenient and. Power outages cause loss of income for power consumers and. It is typically used for test specimen that have small capacitance and as a result the power factor tan delta of the test circuit is rather high. Transformer nameplate ratio, tnr ratio between the specific labelled linetoline voltage of a higher voltage winding to a. Transformers are the most critical part of electrical transmission and distribution network, also when it is come to quality and continuity requirements on delivery of electrical energy.
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