Power transformer testing procedures and schemes photo credit. Use the dmm in ac mode to measure the transformer primary. Windings are the conductors wrapped in various forms like helical, disc, cylindrical, crossover which generates mmf that is carried by the core to other windings for having the different level of voltages. Mainly two types of transformer testing are done at manufacturer premises type test of transformer and routine test of transformer. Transformer types instrument transformers instrument transformers comprise a large category of current and potential transformers for various voltage, frequency and physical size ranges. We have broken them up into several different groupings. Where v 1, e 1, n 1 are the supply voltage, induced emf, winding turns of the primary winding respectively.
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. For equipment that does not have internal switching as above then a 500 volt insulation test is an acceptable alternative. On subtractive polarity transformers the h1 primary lead and the x1 secondary lead will be on the same. Transformer oil is a required addition to electrical transformers. Ensure the ct is connected to system properly in all respect primary and secondary. 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.
Different test like thermography, insulation resistance test, transformer turns ratio test, dissolved gas analysis. Instrument transformer theory and testing steve hudson, pe. Some transformer tests are carried out for confirming the basic design expectation of that transformer. If a threephase transformer is connected as deltadelta dd or starstar yy then the transformer could potentially have a 1. 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. In core type, transformer hv and lv windings are wound on both. They come in many shapes and sizes for different applications they work exactly as you would expect them to. Types of transformer different types of transformer. If the ohmmeters reading is significantly different than the resistance listed on the transformers data sheet, it should be removed and replaced immediately. The various types of transformer shown in the figure above are explained in detail below.
These are the most commonly used transformer types for all the applications. Basics, maintenance, and diagnostics xi contents continued page 9. Transformer oil, a type of insulating and cooling oil used in transformers and other electrical equipment, needs to be tested periodically to ensure that it is still fit for purpose. Insulation testleakage test a leakage test shall be done on appliances that have internal switching that is only activated when the equipment under test is powered at operating voltage. May 10, 20 transformer manufacturers perform two main types of transformer testing type test of transformer and routine test of transformer. Testing consists of measuring breakdown voltage and. There are a variety of transducer types like pressure transducer, piezoelectric transducer, ultrasonic transducer, temperature transducer, and so on. There are a multitude of checks and tests performed as a transformer is being assembled at a substation. Polarity refers to the instantaneous direction of the primary current with respect to the secondary current and is determined by the way the transformer leads are brought out of the case. Types of transformer field tests and diagnostics bright.
Two standardcompliant test electrodes with a typical clearance of 2. Pdf transformer testing type test and routine test of. A simple explanation of the different tests performed on transformers. Just be certain to disconnect the transformer from the circuit before testing to avoid the risk of serious injury. Transformer oil testing is a proven loss prevention technique which should be a part of any condition based predictive maintenance program. In this test, the rated voltage is applied to the primary usually lowv. Therefore, transformation ratio k v 2 v 1 and k e 2 e 1 n 2 n 1 i 1 i 2 also.
If the reading is above the amperage rating for the transformer, the circuit is drawing too much power. Neta is the leading source of specifications, procedures, testing, and requirements. For confirming the specifications and performances of an electrical power transformer it has to go through numbers of testing procedures. The results of the test series show how the breakdown voltage varies with the distance.
Feb 08, 2015 mainly two types of transformer are done by manufacturer before dispatching the transformer mainly 1 type test of transformer and 2 routine test. The transformer oil is filled in the vessel of the testing device. This test is conducted to determine the iron losses or core losses and parameters r0 and x0 of the transformer. There is a saying, pay less for testing during software development or pay more for maintenance or correction later. Types of losses in a transformer there are various types of losses in the transformer such as iron loss, copper loss, hysteresis loss, eddy current loss, stray loss, and dielectric loss. Namely, if testing is based on injecting only one sequence current component at the time on both ct inputs of the transformer differential protection, simple testing procedures can be derived, which are more intuitive, less complex and straightforward than existing phasewise testing procedures.
Air cooled a transformer that is cooled by the natural circulation of air. Cts current transformers pts potential transformers 5. Fat or acceptance test or witness test or joint inspection test is. Depending on the type of the transformer, the input and output. To confirm the physical condition and electrical characteristics of current transformer installed in the installation. During ttr test voltage is applied to one transformer winding. 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. Here we discuss different types of transformers are the step up and step down transformer, distribution transformer, potential transformer, power transformer, 1. Some different types of transformers are power transformers, potential transformers, audio transformers and output transformers. To prove that the transformer meets customers specifications and design expectations, the transformer has to go through different testing procedures in manufacturer premises. Mainly two types of transformer testing are done at manufacturer premises type. Each transformer asset manager must select the amount and type of. Cts are instrument transformers used for converting primary current into a reduced secondary current for use with meters, relays, control equipment and other instruments. A test voltage is applied to the electrodes and is continuously increased up to the breakdown voltage with a constant, standardcompliant slew rate of e.
Type test are conducted on a transformer which is a representative of other transformers. Software testing 4 given below are some of the most common myths about software testing. So, testing the transformer is pretty serious issue. Before proceding with transformer measurements the test engineer will become familiar with the. Transformer is one of the important equipment in power system. The size, type, and location of a transformer dictate the amount of external equipment. The type and routine test are very important for transformer.
All of these factors affect the amount of testing necessary to certify that a transformer is ready to be energized and placed in service. Core and windings of three phase core type transformer. To maximize the life span and effectiveness of a transformer, it is significant to carry out transformer testing to find out possible faults and rectify it in advance. The international electrical testing association neta is an accredited standards developer for the american national standards institute ansi. Transformer testing type tests and routine tests of. This type of transformer is categorized on the basis of a number of turns in the primary and secondary windings and the induced emf. When the primary and secondary have different types of winding connections, star or delta, the overall turns ratio of the transformer becomes more complicated. Sep 26, 2017 mainly two types of transformer testing are done at manufacturer premisestype test of transformer and routine test of transformer. Routine tests and type tests of transformers electrical4u. There are different types of windings used for different kinds of applications and arrangements. Transformers either decrease or increase ac voltage. If the measurement is less than 80 percent of the expected voltage, the fault could lie in either the transformer or the circuitry providing the primary with power. By using inductively coupled electrical conductors as the main agent of transfer, a change in current in the first circuit is carried over to the second circuit, which subsequently assumes the.
As power transformer is highly expensive as well as important part of distribution system. The iec and ieee standard distinguishes between the following types of tests. Testing sequences and procedures are defined by various international standards, many of them set by astm. Types of transformer field tests and diagnostics bright hub. Different types of transducers and their applications. A potential transformer is a conventional transformer having primary and secondary windings. Some transformer tests are also carried out at the consumer site before commissioning and also periodically in regular and emergency basis throughout its service life. These are widely used transformer types for all the applications. These tests are done mainly in a prototype unit not in all manufactured units in a lot. Because these generate a lot of heat that must be removed, they need to be insulated and they have to resist sparking, the physical and chemical properties of certain oils make them ideal for use in transformers and capacitors. There are three basic styles used to transformer system voltages to control voltages. The amperage rating for your transformer fuse may be labeled on the transformer, but will also be. How to use an ohmmeter to test an ac transformer sciencing. There are various test required on transformer to conform performance of transformer.
The transformation ratio of the transformer may be defined as the ratio of the secondary voltage to the primary voltage of the transformer. Here the important thing to remember is that there will not be any difference in primary power and secondary power. Testing potential transformers relay testing training. There are mainly two types of transformer from core construction point of view. Type test and routine test of transformer electrical mastar. Periodically monitoring and preventive maintenance can detect the defects before major damage has been occurred. Let us discuss the use of different types of transducers in practical applications. Transformers are more than just extraterrestrial robotstheyre also highly useful devices for transferring energy between circuits, and there are various different types of electrical transformers. Mainly two types of transformer are done by manufacturer before dispatching the transformer mainly 1 type test of transformer and 2 routine test.
Test this by hooking up the secondary to its circuit and using your dmm to test the secondary lines. Aa an ansi american national standard institute cooling class designation indicating open, naturaldraft ventilated transformer construction, usually for drytype transformers. Universal testing method for power transformer differential. Types of tests electrical equipment testing metrotest. Power transformer testing procedures and schemes eep. A transformer can be classified into various types based on core construction, winding design, application, cooling medium and power supply to which it is connected. Neta defines the standards by which electrical equipment is deemed safe and reliable. Current transformers play an important role in the monitoring and protection of electrical power systems. In addition to that some transformer tests are also carried out at the consumer site before commissioning. Different types of transformers and their applications. Mar 29, 2019 confirm the proper input to the transformer. Nov 17, 2019 core and windings of three phase core type transformer.
The hysteresis losses occur because of the variation of the magnetization in the core of the transformer and the copper loss occurs because of the transformer. Measurement of impedance voltageshort circuit impedance principal tap and load loss short circuit test measurement of noload loss and current open circuit test. In addition some other tests are also carried out by the consumer at site before commissioning and also periodically. Oct 03, 2016 the type and routine test are very important for transformer.
The different types of transformer are step up and step down transformer, power transformer, distribution transformer, instrument transformer comprising current and potential transformer, single phase and three phase transformer, auto transformer, etc. In this paper, the different types of transformer testing are mentioned. The transformer turns ratio test is used to make sure that the ratio between the windings of the primary and secondary coils. Power transformers are usually the most vital link in most industrial and commercial electrical systems, and are among the most reliable components in the system. The different tests conducted in a distribution transformer as per the standards are discussed below. Transformers, dry type, aircooled, lowvoltage, large. Mainly two types of transformer testing are done at manufacturer premisestype test of transformer and routine test of transformer. A variety of types of electrical transformer are made for different purposes. Ratio testing with applied burden is the most accurate and complete approach for testing at ct in service. Transformer insulating fluids testing the purpose of a power transformer is to alter the voltage from that of a distribution rating, to a lower utilization level. The voltage induced in different phases of transformer in respect to neutral.
Despite their design differences, the various types employ the same basic principle as discovered in 1831 by michael faraday, and share several key functional parts. Potential transformers pts or voltage transformers vts pts or vts are the most common device used. A transformer transfers electrical energy from one electrical circuit to another without changing its frequency. Oct 11, 2015 introduction transformers are static alternating current machines principle is based on mutual induction between windings through a common core oilimmersed and dry types power and distribution types special types 6. Different types of transformer winding electrical4u.