This test is performed at or above the rated voltage to determine if there are low resistance paths to the ground or between winding to winding as a result of winding insulation deterioration. Performance test of faulty distribution transformers along. Page 1 of 14 standard work practice sp0504 ver 4 ergon energy corporation limited abn 50 087 646 062. Transformer testing has developed considerably over the past years. The ac hv test value should not surpass 75% of the factory test value. Aug 05, 2016 video lecture on open circuit test and short circuit test on transformer of chapter single phase transformer of subject basic electrical engineering for firstyear engineering students. In addition some other tests are also carried out by the consumer at site before commissioning and also. It can be used to power up to four hayward universal. Participants will receive instruction on the filtering and drying out process to be performed on transformers.
Method 1 substation with a single transformer when the plant foresees installation of an. The megger insulation tester is essentially a highrange resistance meter ohmmeter with a builtin directcurrent generator. Test this by hooking up the secondary to its circuit and using your dmm to test the secondary lines. The testing plant parameters are such adjusted to give the rated short circuit current. The low voltage distribution networks are supplied from mvlv substation transformer that represent the last step of bringing transformation to the low voltage and ensuring the protection and monitoring of the network. The productionlinehipot test is used to determine whether the construction of a production unit is about the same as the construction of the unit that was subjected to type testing. Mainly two types of transformer are done by manufacturer before dispatching the transformer mainly 1 type test of transformer and 2 routine test. September 5 7, 2018 diagnostic testing overall dga oil screen.
Higher line terminal voltage than can occur in the field 2. Hv earth isolate the power supply to the transformer connect the hv live part of the terminal to the earth by connecting with. Transformers experience power loss due to load resistance, which you can test with an ohmmeter by touching the meters red and black pins to opposite ends of the transformers wiring. Transformer components low voltage bushings for padmounted distribution transformers technical information guide abb low voltage bushings terminate a transformer s internal low voltage leads at the tank wall and provide a standard threaded stud for connections to the external low voltage circuit. A voltmeter, wattmeter, and an ammeter are connected in lv side of the transformer as shown. 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. Find here insulation testing and continuity, power protection, power transformer testing, power cable infrastructure, cable fault location, general electrical test. A presentation ontransformer testing using dpatt3bi 2. Testing manual for electrical equipment nahed alhajeri 1and anantha madhavan 2 abstract quality assurance qa refers to a program for the systematic monitoring and evaluation of the various aspects of a project, service, or facility to ensure that standards of quality are being met. Check nameplate ratings and hv, lv terminal markings. The following tests are routinely conducted in the field on the transformer. Standard for acceptance testing specifications for electrical.
Maintenance personnel must manage moisture, heat, and oxygen, while attempting to protect the power transformer from dielectric, thermal, and mechanical failure modes. The first neta acceptance testing specifications for electrical power equipment and systems was produced in 1972. Warning failure to remove pressure test plugs andor plugs used in winterization of the poolspa. Lv transformer electrical substation consists, therefore, of the set of devices dedicated to the transformation of the voltage supplied by the distribution network at medium voltage e. Power transformers vsd transformers converter duty. Testing power transformers highvoltage transformers are some of the most important and expensive pieces of equipment required for operating a power system. P assistant professor department of electrical and electronics engineering loyola institute of technology and science loyola nagar, thovalai, tamilnadu629302, india email. Tap changer is operated by means of a handle on the cover or a hand wheel on top or on sidewall of the transformer. The megger insulation tester is a small, portable instrument that gives you a direct reading of insulation resistance in ohms or megohms. To conduct a performance test whether the transformer is faulty or not, a given low voltage of about the single phase value vphv l 3. Transformer testing equipment catalogue there are several facets to a transformer s overall health, so a full assessment requires a number of tests.
The test measurement values are affected by variables such as temperature, humidity, test voltage, and size of the transformer. Oct 25, 2018 insulation resistance tests megger test are carried out on all windings, core and core clamping bolts. Check the value after one minute and record the steady value. 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. These devices use standard transformer theory with 23 windings one primary with one or two secondary windings with a magnetic connection via an iron core. Expected for a 5 legged core or shell type transformer with a delta connected secondary winding. The transformers shall be double copper wound, three phase, oil immersed with onan cooling.
Testing of power transformers seems like a similar experience. We just apply three phase 415 v supply to hv winding, with keeping lv winding open. The core of a transformer is made of iron whereas thewinding which. What is the megger test procedure for transformers. Ir values a for 3311 kv power transformer 2500 v megger is to be need. The wire itself is usually copper or aluminum, which is known to be a good conductor of the electric current that powers your equipment. Check that all parts of the transformer are properly assembled and tight. Upon completion of this project, the neta technical committee began work on a maintenance document, and maintenance testing specifications for electrical power equipment and systems was published in 1975. A catalogue, for quick reference, of the range of megger test instruments for the maintenance of electrical power systems. In this book we have laid down important aspects on transformer.
There are three basic styles used to transformer system voltages to control voltages. Power transformer testing procedures and schemes photo credit. 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. We measure the induced voltages at hv and lv terminals of the transformer to find out actual voltage ratio of the transformer. Video lecture on open circuit test and short circuit test on transformer of chapter single phase transformer of subject basic electrical engineering for firstyear engineering students. When ac hipot tests are used for routine maintenance, the power transformer can be examined at rated voltage for 3 min instead of testing at 65% of factory test voltage. Distribution transformer testing power partners usa. The vector group of transformer is an essential property for successful parallel operation of transformers. Power transformer testing procedures and schemes eep. The insulation must be just the opposite from a conductor. The rectiers used in low voltage vsds are usually both 6pulse or 12pulse rectiers, and they may be diode bridges, thyristor bridges or power transistor solutions. The procedure of the transformer ratio test is simple. Electrical substations can also be divided into public and. In addition some other tests are also carried out by the consumer at site before commissioning and also periodically.
The 6pulse recti er is supplied by a twowinding transformer and the 12pulse rectier needs a threewinding transformer, having two separate secondary windings with 30 phase shift. Transformer testing type tests and routine tests of. Potential transformers pts or voltage transformers vts pts or vts are the most common device used. This course provides technical information about the design, construction, maintenance and the significance of various site tests that are carried out on high voltage transformers.
Megger offers the broadest range of transformer test equipment in the industry, capable of delivering the most comprehensive picture of transformer health. Open as well as shorted terminals of nontested windings conclusions. The following sections of the ansineta standard for acceptance testing specifications for. Basics, maintenance, and diagnostics xi contents continued page 9. The voltage at rated frequency is applied to that lv side with the help of a variac of variable ratio auto transformer the hv side of the transformer is kept open.
Connect the lv live part of the terminal to the earth by connecting with. The complete guide to electrical insulation testing. The transformer s nameplate is compared to manufacturing information for style, serial number, kva, hv rating, lv rating, tap voltages, impedance, conductor. Feb 08, 2015 there are various test required on transformer to conform performance of transformer. Power transformer testing transformers may be tested using ac or dc voltage. Routine tests and type tests of transformers electrical4u. Understanding the condition of the power transformer is essential.
There are various test required on transformer to conform performance of transformer. Designed for the rigorous demands of ac and dc motor drive loads. If the reading is above the amperage rating for the transformer, the circuit is drawing too much power. The transformer permits the use of multiple voltages in the design of the system. Includes test with shorted terminals of untested windings 4.
Testing for power transformers charles sweetser omicron. Measurement of the harmonics of the noload current. Before conducting a transformer winding resistance test, it is important to observe all safety warnings and take proper precautions. For good insulation, the resistance usually reads in the megohm range. Therefore, transformer under test may be demagnetized before commencement of magnetizing current test. Our long experience with all types of distribution transformers translates into reliable products for any application, while our new trihal iot connected features allow you to take a step forward in efficiency. Open circuit test and short circuit test on transformer.
Vector group test of power transformer electrical4u. Measurement of zerosequence impedance of threephase transformers. Losses of transformersthe transformers are made of 2 types of materials. Impulse test concepts by philip j hopkinson, pe good impulse test. The amperage rating for your transformer fuse may be labeled on the transformer, but will also be. Low voltage distribution transformers, three phase. May 10, 20 the transformer testing performed before commissioning the transformer at the site is called the precommissioning test of transformer. Medium voltage products technical guide the mvlv transformer. A free powerpoint ppt presentation displayed as a flash slide show on id. Able to excite all natural frequencies of the windings ideal impulse test 1. 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. It evolved from the simple gonogo verdict into a sophisticated segment within transformer manufacturing.
Some advantages to designing a system with low voltage transformers. In distribution side transformers there are commonly two. This course uses uptodate test equipment and procedures for evaluating the condition of a transformer. The induced voltage on the low voltage side of the transformer is connected to the low voltage terminals of the ratio meter. Design, supply, installation, testing and commissioning of 15 mva, 6611kv, 3 phase, 50hz, power transformer with on load tap changer at main receiving station rail wheel factory yelahanka, bangalore. Whether you test monthly, twice a year, or once a year depends upon the type, location, and importance of the equipment.
The wire itself is usually copper or aluminum, which is known to. Lv transformer electrical substation consists, therefore, of the. The high voltage winding of the transformer under test and the high. Ac voltage is preferable to dc voltage for transformer testing because ac voltage simulates the internal stress that the transformers face during operating conditions. Some of the most commonly occurring failures of the transformer and their causes are listed below. The standard megger testing equipment is used, the line terminal of which is connected to the winding or core bolt under test. The bidder should be original equipment manufacturer oem. Porcelain bushings lv series a triedandtested mediumvoltage bushing for distribution transformers. Standard for acceptance testing specifications for. The connection diagram for open circuit test on transformer is shown in the figure 1. We repeat the test for all tap position separately. General visual inspection and compliance with the drawings and manuals. Power transformer testing swp check this is the latest process zone version before use. Special test transformer nameplate data year of manufacture 2006 rated power hvmv for onan, kva 468468 rated voltage hvmv lv, kv 224.
Low high low lhl pattern will be obtained on a 3legged core type transformer if the traditional test protocals are not followed. Just be certain to disconnect the transformer from the circuit before testing to avoid the risk of serious injury. Short circuit test and differential stability stable condition. 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 connection diagram for open circuit test on transformer is shown in the figure. This test is performed with an ohmmeter to verify that the internal wiring is correct. The purchase, preparation, assembly, operation and maintenance of transformers represent a large expense to the power system. Hv the test voltages will be limited and should not exceed the line toground rating of the insulation system. This test is performed on all transformers to verify transformer circuit and component integrity. During the impregnation of the transformer it is po ssible to reach the max temperature of 110c in oil and 120c in air for. The voltage at rated frequency is applied to that lv side with the help of a variac of variable ratio auto transformer. Check the cable connections on the lv side and the markings. Scribd is the worlds largest social reading and publishing site. Open and short circuit test of transformer electrical4u. Understanding the value of electrical testing for power. Distribution transformers maintenance guide for liquid.
Aug 16, 2014 this test is performed at or above the rated voltage to determine if there are low resistance paths to the ground or between winding to winding as a result of winding insulation deterioration. It also covers practical methods of transformer testing including routine tests for postfault and preventive maintenance. In a shelltype shell form transformer, the steel magnetic circuit core forms a shell surrounding the windings. Students learn instruction to install, maintain, repair or troubleshoot power transformers rated 765 kv or less. This paper is going to focus on a subset of electrical diagnostic tests. Some of the process failures that can be detected by a productionline hipot test include, a transformer wound in such. Transformer precommissioning tests and afterreceipt. There should not be any mechanical distortion, fire to the transformer during this test. Medium voltage transformers discover our range of drytype, oil and power transformers from medium voltage up to 170kv.