Before proceding with transformer measurements the test engineer will become familiar with the safety rules of section 2. Diagnostic testing of instrument transformers 5 mb omicron. The instrument current transformers supply, and isolate, the secondary relays, meters and other instruments, providing the suitable and manageable secondary quantities which are proportional to those in the primary. Ct is essentially tested as a voltage transformer by applying voltage to the ct secondary and measuring the primary. On theother hand, when j is large, then theuse of a detector of highimpedance may shift theload from transformer of higher. Download the seminar report for testing of transformer. Transformer testing has developed considerably over the past years. Use small jumper to short the ct secondary from ct box, the measurement will be gone at panel. Authors paul price, nate myers, jim dehaan bureau of reclamation hydropower technical services group denver, colorado 5d. The current transformer is solely assessed through its external behavior without considering what is happening inside. Close the air circuit breaker of lowvoltage power distribution cabinets step by step. Common electrical tests on power transformers omicron.
A test with this method at rated voltages currents is mandatory for every it as part of the routine tests. Traditional current transformer testing follows a blackbox approach. A test set operator connects the leads, pushes the buttons, and records the. Pdf a method for testing electronic instrument transformers is described, including electronic voltage and current. When current flow exceeds that rating, the metering core will become saturated, thereby limiting the amount of current level within the device. In this book we have laid down important aspects on transformer testing in order to enhance the understanding of the testing procedures and its outcome. For distribution transformers, the magnitude of the short circuit current, the numbers of shortcircuit tests and. Routine tests and type tests of transformers electrical4u.
Measurement shall be carried out with direct current dc by the voltage drop method or the bridge method as specified in the manufacturer approved power transformer testing procedure. Different test devices and methods are used in the market to verify the performance of current transformers cts during development, production, installation and maintenance. The amperage rating for your transformer fuse may be labeled on the transformer, but will also be. Fist 38, operation, maintenance, and field test procedures for protective relays and associated circuits 5a. Magnetization and primary injection test of current transformer for protective relaying jacob tsado 8 current transformers. Easy method for testing transformer differential relays cigre 2009 moscow. Check for cracks in door current transformers, and that equipotential point of window type cts has been connected to the busbar. These tests are done to assess the condition of transformer after installation and compare the test results of all the low voltage tests with the factory test reports. Inspect transformer and parts for shipping damage and moisture.
The current standards relating to short circuit strength are ansi c57. Electrical testing methods on instrument transformers. Insulation tests on current transformers rated 600v or less are usually performed at vdc. This amounts to a rigorous examination of the transformer intended to. The test and assessment of transformers is a complicated task. Transformer, operation, testing and maintenance 33kv and below 9. Parameters of short circuit testthis is a big advantage of dpatt3bi that it can be usedfor transformer testing. The core of a transformer is made of iron whereas thewinding which is wrapped over the iron core is made up ofcopper.
Test procedure for thermal evaluation of insulation systems for ventilated drytype power and distribution transformers. After the current transformers have been subjected to the dielectric type tests 3, 4 and 5 they shall be subjected to all the routine. This protects connected metering devices from overloading in the presence of fault level current flows. Instrument transformer testing instrument transformers for metering purposes must have a high degree of accuracy up to class 0. In this book we have laid down important aspects on transformer. Short ct links then isolate the external wiring to confirm ct circuit will not be opened. This ms excel spreadsheet is actually detailed instruction for each procedure necessary for correct testing of power transformer. Hence, it is essential to inspect and calibrate those instrument transformers at regular intervals. Basics, maintenance, and diagnostics xi contents continued page 9. Dry type transformer testing procedure december, 2017 how to shift gears of the dry type transformer. Before conducting a transformer winding resistance test, it is important to observe all safety warnings and take proper precautions.
Once you have completed the testing, you can also demagnetize the transformer. Efficient current transformer testing with omicron ct analyzer. Check for level, colour of oil in the sight glass for outdoor current transformers. 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. Cn104330763a test method for bushing current transformer of. It evolved from the simple gonogo verdict into a sophisticated segment within transformer manufacturing. Losses of transformersthe transformers are made of 2 types of materials. Power transformer testing procedures and schemes photo credit. Pdf method of current transformer metrological properties. Measurement of no load loss and current open circuit test.
Back to the basics current transformer ct testing as test equipment becomes more sophisticated with better features and accuracy, we risk turning our field personnel into test set operators instead of skilled field service technicians. Operation, maintenance, and field test procedures for. Current transformers play an important role in the monitoring and protection of electrical power systems. Pdf easy method for testing transformer differential relays.
Ct analyzer current transformer testing, calibration and. In this test we confirm the ct secondary connection. The following tests are routinely conducted in the field on the transformer. Ieee guide for test procedures for thermal evaluation of insulation systems for solid cast and resinencapsulated power and distribution transformers. Power transformer testing fat test inspection for industry. Remove the neutral ground and isolate the ct from any associated burden. This article describes an innovative solution to test cts at all lifecycle stages by using a new testing method called the. The basics of current transformers nk technologies. The following sections of the ansineta standard for acceptance testing specifications for. May 10, 20 the transformer testing performed before commissioning the transformer at the site is called the precommissioning test of transformer. Turnsratio test results should not deviate more than onehalf percent from either the adjacent coils or the calculated ratio. A primary part of commissioning a transformer involves testing it after its installation in the field. Meggers range of current transformer test equipment allows you to construct an in depth test and maintenance programme to prevent problems before they occur. Ac voltage is preferable to dc voltage for transformer testing because ac voltage simulates the internal stress that the transformers face during operating conditions.
Transformer differential protection 7ut6 siprotec 4 7ut6 differential protection relay for transformers, generators, motors and busbars. Back to the basics current transformer testing ct as test equipment becomes more sophisticated with better features and accuracy, we risk turning our field personnel into test set operators instead of skilled field service technicians. Ensure the ct is connected to system properly in all respect primary and secondary. Testing of power transformers seems like a similar experience. The voltage ratio shall be measured on each tapping and verified aginst manufacturer approved power transformer testing procedure. The typical excitation current test data pattern for a threelegged core transformer is two similar current readings and one lower current reading. Current transformer ct testing procedure in sulation resistance measurement. Current transformers testing and commissioning guidelines. A routine series of diagnostics and testing for your current transformer should include ct saturation testing to identify the knee point against ieee or iec standards, ct ratio tests to identify that the voltage ratio is within expected parameters and current transformer resistance testing for both the transformer windings and ct insulation. Nov 26, 2010 traditional current transformer testing follows a blackbox approach. By comparing test data taken after the fault to previous test data, damage to the transformer can be determined. Sep 28, 2018 current transformer ct testing procedure in sulation resistance measurement.
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. Ensure that all equipment to be tested is properly grounded and treat all highvoltage power equipment as energized until proven otherwise by using the proper lockouttagout procedures. Transformer testing allows this aging process to be quantified and tracked, to help predict replacement intervals and avoid failures. To ensure that a current transformer is accurately monitoring the current, the metering or the relaying accuracy of the current transformer is verified. Procedure for current transformer factory and site.
Historical test data is valuable for determinll damage to the transformer after a fault or failure has occurred elsewhere in the circuit. 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. Easy method for testing transformer differential relays. A test set operator connects the leads, pushes the buttons, and records the results. Standard for acceptance testing specifications for.
A presentation ontransformer testing using dpatt3bi 2. Making a wellinformed choice in equipment for transformer testing is an important step towards ultimately improving transformer life management decisions. Precautions should be taken when making this test on current transformers to. Back to the basics current testing valence electrical. Transformer testing equipment catalogue there are several facets to a transformers overall health, so a full assessment requires a number of tests.
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. Standard for acceptance testing specifications for electrical. Medium and high voltage eis transformer testing with ieee. Heres a summary of the current transformer testing paper. Transformer testing commissioning, routine, diagnostic. Tm 5686 power transformer maintenance and acceptance. Following is an approximate sequence for transformer testing. Some transformer tests are carried out for confirming the basic design expectation of that transformer. These tests are done mainly in a prototype unit not in all manufactured units. Winding resistance test procedure iec, nec, nema, fdf, iso ansi, ci, ipcea iec, nec, nema, fdf, iso ansi, ci, ipcea procedure h r a 8 power transformer winding ratios test procedure iec, nec, nema, fdf, iso ansi, ci, ipcea iec, nec, nema, fdf, iso ansi, ci, ipcea procedure h r a 9 power transformer temperature rise test.
Ct analyzer the number one in current transformer testing. We also offer solutions for testing bushingtype current transformers for. The dc voltage test momentarily imposes a small dc voltage on one side of a ct primary and the direction of the momentary deflection of a meter on the opposite side secondary. Procedure for current transformer factory and site acceptance tests note. Magnetization and primary injection test of current.
Power transformer testing procedures and schemes eep. Power transformer testing transformers may be tested using ac or dc voltage. The value of full load current for transformers of different ratings is shown in the following table. The name instrument transformer is a general classification applied. With our testing system, you can use a single device to determine all of these parameters in an easy way. Prior to testing, short the primary winding of the ct under test by connecting h1 and h2, then short the secondary winding of the ct under test by connecting x1 and x2x5.
The test method for the bushing current transformer of the main transformer includes that when testing the transformation ratio, polarity, voltageampere characteristics and the like of the bushing current transformer of one side of the main transformer, using a testing device to exert alternating. To prove that the transformer meets customers specifications and design expectations, the transformer has to go through different testing procedures in manufacturer premises. Transformer testing electrical transformer manufacturer. Pdf electronic voltage and current transformers testing device. Test this by hooking up the secondary to its circuit and using your dmm to test the secondary lines. Megger offers the broadest range of transformer test equipment in the industry, capable of delivering the most comprehensive picture of transformer health. Testing current transformers ratio vs applied burden cts installations can be fully verified in the field we can verify that the ratio is correct and constant as burden changes. A current transformer monitors a current that passes through an electrical apparatus such as a power transformer, a generator, or a circuit breaker. To confirm the physical condition and electrical characteristics of current transformer installed in the installation. On pressing button 3 of the keypad of dpatt3bi, wpf page appears on the lcd display showing copper losses. The invention discloses a test method for a bushing current transformer of a main transformer. Pdf during transformation of power frequency currents inductive current.