While testing, basic testing requirements and testing codes are set out in the national and international standards. Insulation resistance tests megger test are carried out on all windings, core and core clamping bolts. Power transformer type, routine and special tests include measurement of. The only ttr available at one time was a singlephase unit that was cranked by hand to produce an output voltage of 8v. Home download center electrical engineering books and technical guides power substation guides guidelines to power transformer type, routine and special tests introduction to methods the methods used during tests and measurements of the power transformers, test and measurement circuits, calculations and evaluation criterias are included in this manual. The connection diagram for the short circuit test on the transformer is shown in the figure below. Bar type cts operate on the same principle of donut cts but have a permanent bar installed as a primary conductor.
The product has been tested according to relevant parts of the standards stated below. Mainly two types of transformer testing are done at manufacturer premises type test of transformer and routine test of transformer. Type tests are tests made on a transformer which is representative of other transformers to demonstrate that they comply with specified requirements not covered by routine tests. Routine tests are performed during manufacturing on all transformers after the active part assembly completed and according to ts 267, iec 76 etc. These are the most commonly used transformer types for all the applications.
What is the megger test procedure for transformers. Types of transformer different types of transformer. The voltages at the winding couples to be measured, can be measured at the same time and the ratio can be determined, or digital instruments which are manufactured for this purpose can be used in the voltage ratio measurement method. Guidelines to power transformer type, routine and special. Resistance measurements, voltage ratio, loss measurements, etc. The iron core inside the transformer is magnetized. Dry type transformers are a large part of the electrical infrastructure for many industrial and commercial sites. For conducting heat run test on the three phase transformer, full rated. That means routine tests of transformer include all the type tests except temperature rise and vacuum tests. Apprentice electrical technician test ett preparation guide. Therefore, ensuring the performance of electrical testing and maintenance on critical transformers is very important to electrical system reliability. Optional perform a powerfactor or dissipationfactor tipup test on windings rated greater than 2.
In addition to that some transformer tests are also carried out at the consumer site before commissioning. Type or design1 tests are conducted on a transformer which is representative2 of other transformers, to demonstrate that these transformers comply with specified requirements not covered by routine tests. Turns ratio the turns ratio test, also known as a ttr transformer turns ratio is, like most tests, easier to perform now than it used to be. No matter what the type, winding resistance testers are always equipped with a current output, voltage measurement, and resistance meter. Understanding the value of electrical testing for power. Guidelines to power transformer type, routine and special tests photo credit.
The standard megger testing equipment is used, the line terminal of which is connected to the winding or core bolt under test. Transformers multiple choice questions and answers mcqs electrical engineering interview transformers viva lab manual pdf free download skip to content engineering interview questions,mcqs,objective questions,class notes,seminor topics,lab viva pdf free download. Codes of mode and the cooling type of transformers are constantly supplemented through periodic changes to the standards, due to the development of cooling systems. 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. All of these factors affect the amount of testing necessary to certify that a transformer is ready to be energized and placed in service. The resistance of an alternating current ac transformer is held within the wires wound around its core. Open and short circuit test of transformer electrical4u. The earthing transformer shall have 100% impedance to allow rated fault current at rated system voltage in the event of occurrence of a solid single phase to ground fault. Transformer testing type test and routine test of transformer electrical4u. This test is conducted to determine the iron losses or core losses and parameters r0 and x0 of the transformer. Depending on the type of the transformer, the input and output windings. Ieee standard distinguishes between the following types of tests. The battery negative terminal is connected to current transformer terminal h2 and the positive side is left hanging for.
Abb dry type network transformers the average life of vault type network transformers is shortened due to high overloading and tank deterioration enclosure tanks are designed with thick walls and epoxy coatings to impede rustthrough internal faults or short circuits can lead to large, street level events that cause significant harm. Type test edition 08 division energy management date 20180615 digital grid transformer differential protection v07. The size, type, and location of a transformer dictate the amount of external equipment. Oil pressure test on transformer to check against leakages past joints and gaskets. This type of transformer is categorized on the basis of a number of turns in the primary and secondary windings and the induced emf. Cts for metering purposes must have a high degree of accuracy to ensure accurate billing while those used for protection must react quickly and correctly in the event of a fault. Transformers, dry type, aircooled, lowvoltage, large. Transformers are an electrical component that transmit electrical energy between at least two circuits. The insulation condition of component parts of the transformer i. Testing is the most important activity when any equipment is designed. The connection arrangement for a kick test for a current transformer is presented in figure 3. Expected for a 5 legged core or shell type transformer with a delta connected secondary winding. Auxiliary parts of the transformer are also not included, except as indicated e. Apprentice electrical technician test ett about the test there are 40 questions with a maximum time limit of three hours.
This early warning system can allow maintenance management to identify maintenance priorities, plan work assignment schedules, arrange for outside service, and order. How to test transformer dc winding resistance of transformer by jyr20s kingrun, china. 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. Open circuit test and short circuit test on transformer. Testing power transformers highvoltage transformers are some of the most important and expensive pieces of. The importance of current transformer tests is often underestimated. Transformer tests eep electrical engineering portal. This test reproduces conditions of continuous rated load and the temperature rise occurring during the load. Mainly two types of transformer are done by manufacturer before dispatching the transformer mainly 1 type test of transformer and 2 routine test. During ttr test voltage is applied to one transformer winding.
Insulation resistance test of transformer is one of the most important transformer tests we can perform this test at factory or site this test can be classified under type test, routine test, precommissioning and commissioning tests, periodic maintenance transformer tests you can know more about transformer testing and its. Bar and donut type cts do not have a physical primary winding and are considered to have one primary turn. The various types of transformer shown in the figure above are explained in the detail below. As it checks the quality of material used and the procedure of transformer manufacturing hence provide us details of life of transformer, the transformer behaviour on different faults. The methods used during tests and measurements of the power transformers, test and measurement circuits, calculations and evaluation criterias are included in this manual. A dga test can identify an overloaded transformer by a test result showing high carbon monoxide, high carbon dioxide, and in extreme cases, even elevated methane and ethylene. Test lab cast resin transformers christopher kammermeier gttp document no 02. The ac hv test value should not surpass 75% of the factory test value. Home download center electrical engineering books and technical guides power substation guides guidelines to power transformer type, routine and special tests introduction to methods the methods used during tests and measurements of the power transformers, test and measurement circuits, calculations and evaluation criterias are. There are various test required on transformer to conform performance of transformer. Guide for field pd tests for liquidfilled power transformers.
Special costumer standards or values are not included. Wound cts have a primary and secondary winding like a normal transformer. The oil pressure test on transformer to check against leakages past joints and gaskets is. The transformers are classified based on voltage levels, core medium used, winding arrangements, use and installation place, etc. In addition some other tests are also carried out by the consumer at site before commissioning and also. Jan 16, 2018 ir testing dry type transformer wilmar gomez. Test lab cast resin transformers christopher kammermeier document no 02. Routine tests and type tests of transformers electrical4u. If not indicated, the description is for a twowinding transformer.
Common precommissioning tests of transformer insulation resistance values of various winding should be checked. Along with different precommissioning tests, different instruments associated to the transformer also to be checked. Opencircuit or noload test in this test secondary usually high voltage winding is left open, all metering instruments ammeter, voltmeter and wattmeter are connected on primary side and normal rated voltage is applied to the primary low voltage winding, as illustrated below. Measurement of noload loss and current open circuit test. In a shelltype shell form transformer, the steel magnetic circuit core forms a shell surrounding the windings. Transformer testing preliminay test carried out on transformer before it is put into the tank. This is a closed book test and calculators are allowed. 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. 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.
So, insulation overheating measurement is also transformer oil testing methods. Product type transformer protection ied type ret670 v2. Power transformer all tests in hindi before erractig. By using such instruments, in addition to measuring the turn. Connection on cpc100 will be same as the shown figure. Here we discuss different types of transformers are the step up and step down transformer, distribution transformer, potential transformer, power transformer, 1. Measurement of impedance voltageshort circuit impedance principal tap and load loss short circuit test. Type test are conducted on a transformer which is a representative of other transformers, to demonstrate that these transformers comply with specified requirements not covered by routine tests. Tests types and test laboratory capacity the test laboratory of asea brown boveri, s. Transformers regulate the voltage in circuits, but in some cases these can go bad and cause a circuit to not. So for ensuring proper performance of electrical power transformer, voltage and turn ratio test of transformer one of the important tests. 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. Nov 17, 2019 after, installation of power transformer, several precommissioning tests to be done before putting the transformer in service.
Measurement of impedance voltageshort circuit impedance and load loss short circuit test. A test set used for a power transformer would be much different than one designed for small instrument transformers. As power transformer is highly expensive as well as important part of distribution system. This is a general test description for castresin and dry type transformers. The scope of this chapter describes type tests, this means the standard require these tests for a new design or significant design changes. The most frequent mode of failure for dry type transformers is insulation breakdown resulting in interturn faults which leads to more severe faults such as phase to phase winding or earth faults.
Scope this is a general test description for castresin and dry type transformers. Pdf transformer testing type test and routine test of. This test also performed as a routine test of transformer. The wiring of field pd tests the way of wiring is recommended according to the type and voltage level of a power transformer by taking account of field test environment. Noise measurement of transformer 112 mva the test procedure is in accordance with iec standard 6007610. Dissolved gas analysis is the most commonly used method for determining winding insulation condition in oil type transformers, but is not possible for dry type transformers. So transformer ratio test is an essential type test of transformer. Theory heat run test is one of the type tests on power transformer. Low high low lhl pattern will be obtained on a 3legged core type transformer if the traditional test protocals are not followed. The tests this laboratory is able to carry out are the. Reference materials ett test contains questions on the following. Transformer manufacturers perform two main types of transformer testing type test of transformer and routine test of transformer.
Special tests are tests other than type or routine tests agreed to by the manufacturer and the purchaser. Neta defines the standards by which electrical equipment is deemed safe and reliable. Guidelines to power transformer type, routine and special tests eep. Different types of transformers and their applications.
There are a multitude of checks and tests performed as a transformer is being assembled at a substation. Each transformer asset manager must select the amount and type of. Repeat the test for the other phases and the other secondary cores. The international electrical testing association neta is an accredited standards developer for the american national standards institute ansi. A low voltage of around 510% is applied to that hv side with the help of a variac i. Transformer oil testing is a proven loss prevention technique which should be a part of any condition based predictive maintenance program. When current flows through the primary winding, the following actions occur. Some tests are done at manufacturer premises before delivering the transformer. A voltmeter, wattmeter, and an ammeter are connected in hv side of the transformer as shown. Oct 03, 2016 the type and routine test are very important for transformer.
1279 673 83 602 959 489 225 1261 1226 477 2 363 55 203 501 257 672 1189 1060 1173 742 497 1058 823 1474 1340 1350 1441