The role of sfra is growing in the transformer field and the results interpretation is becoming more and more important day by day. If you are running a version of sfra software older than v5. Safety information dangerous voltages can occur on the connectors, even though the auxiliary voltage has been disconnected. 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. On the other hand, the load on the transformer can only be. Main core deformation, open circuits, shorted turns, residual magnetism. The mrct will directly connect to multi ratio cts and perform all tests saturation, ratio and polarity, winding resistance and insulation on all taps with the push. Sometimes it becomes impossible to check the oil level without opening the transformer. The preference is that all large power transformers 1 mva be tested with ttr test set.
V winding in succession and measuring all the other voltages both on high voltage and low voltage side. Pdf experiences of sweep frequency response analyser for. Sweep frequency response analysis sfra sea trasformatori. The current transformer shall be subjected to the appropriate specified powerfrequency pre stress voltage given in table 2b for 1o seconds. Transformers while experiencing severity of short circuit current loses its mechanical property by way of deformation of the winding or core. Interpretation of sweep frequency response analysis sfra. The winding of transformer may be subjected to mechanical stress. Frequency response analysis on power transformers omicron. The latest sfra test sets make these techniques more accessible, more convenient and. Sep 26, 2017 mainly two types of transformer testing are done at manufacturer premisestype test of transformer and routine test of transformer. Test systems are available with fixed meter racks or with moveable trolleys and gantries.
May 15, 2016 sfra stands for sweep frequency response analysis. Testing power transformers highvoltage transformers are some of the most important and expensive pieces of equipment required for operating a power system. Shorted turntoturn insulation, short circuited core laminations, loosening of the core clamping, or. The transformer to be tested must be completely isolated from the power system. What is the importance of the sfra test in a transformer. It is assumed that you are familiar with professional standards and safety practices. The results and experience accumulated over more than 12 years have shown that, in completion to gis equipment and hvcable systems, large hv power transformers can be also tested on site. Instrument transformers for metering purposes must have a high degree of accuracy up to class 0. M5200, m5300, or m5400 sweep frequency response analyzer. 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. Partial discharge analysis on power transformers omicron.
It has been developed with the assistance of bureau of reclamation engineers. Normally transformer is supplied with gas filled i. It is useful to correlate the two methods to increase the precision of the result. 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. A transformer is a passive electrical device that transfers electrical energy from one electrical. In this paper the method of sweep frequency response analysis sfra has been proposed for onsite and instant test of oil condition without requiring the transformer to be.
Feb 08, 2015 there are various test required on transformer to conform performance of transformer. Apply the m5400 during factory tests, after transportation, crane delivery, system faults or even routine maintenance in order to get a baseline test. In addition some other tests are also carried out by the consumer at site before commissioning and also. The more indications are positive, the more certain is similarity of coreandcoil assembly. The endtoend sfra connection is one of the most commonly used connections of the sfra test. Procedure for current transformer factory and site acceptance tests 765 765 1800 0 2100 1425 2400 1550 method 2. Power transformer faults identification using sfra t.
When a transformer is subject to sfra testing, the leads are configured to use four terminals. The transformer was immediately taken offline and internally inspected to identify any problems. What is the correct procedure for dvdf and hv test on. The type and routine test are very important for transformer. 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. On distribution transformer this type of switch may also be used to change nameplate voltage andor configuration. Frequency response analysis often referred to as fra or sfra is a powerful and sensitive method for testing the mechanical integrity of transformer cores, windings, and press frames, in power transformers. Free transformers online practice tests 15 tests found for transformers aieee physicstransformers 10 questions 421 attempts aieee physics,iit jee physics,xii cbse,i. Unlike the tests described previously, in the present case nominal voltage is applied. Sfra, detect of winding deformation in power transformer. Nonobservance can result in death, personal injury or substantial. Portable ct pt analyzertransformer testgfuve electronics. The oil can only be filled in the transformer which satisfies the standard specifications mentioned by the manufacturer of transformer.
This test also performed as a routine test of transformer. Connection on cpc100 will be same as the shown figure. The technique of sfra is a major advance in transformer condition monitoring analysis. Without the need for a pc to compare transformer fingerprints, the sfra 5000 decreases test time enabling the engineer to. Sfra testing basics offline test the transformer is seen as a complex impedance circuit open excitation current and short shortcircuit impedance responses are measured over a wide frequency range and the results are presented as magnitude response curves filter response changes in the impedance can be. Nowadays, a vast number of transformers operate worldwide aiming to provide reliable and safe operation under. On site oil test for a transformer using sweep frequency. The dedicated transformer test van helps you perform a range of routine electrical tests and advanced. These four terminals can be divided into two unique pairs one pair each. Since the invention of the transformer, the design, quality and efficiency of this magnificent machine has been improved thanks to the development of electromagnetic materials, computer design algorithms, insulation materials, cooling systems, structural design, etc. Procedure for current transformer factory and site. Use it to help determine how a transformer is deteriorating, if it can go back in service after a fault or if it has been damaged during transit.
Final report by power transformers evaluation standards. Free online quiz test transformer theory and practice. Partial discharges pd, as defined by iec 60270, are localized dielectric discharges in a partial area of a solid or liquid electrical dielectric insulation system under highvoltage field stress. Constructional features of three phase transformers three phase. The procedure of the transformer ratio test is simple. Sfra 5000 is a standalone sweep frequency response analyzer for the high accuracy transformer analysis and integrates the sts and td 5000 family test sets. Power outages cause loss of income for power consumers and. 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. Abbs onsite repair is achieved by bringing the transformer factory setup to the. Mlgw began to test each of its transformers for furans in 2009.
Pdf interpretation of sweep frequency response analysis. Trafositetesting impulse testing lightning and switching english pdf. Transformer tests routine tests are applied to all transformers through with manufacturing. Ms excel spreadsheet electrical engineering portal. A typical excitation current test data pattern for a threelegged core is two similar current. This test is very reliable for condition monitoring of physical condition of transformer windings. In addition to that some transformer tests are also carried out at the consumer site before commissioning. The gf106t ct analyzer is mainly used for field testing of p class ct and pt. The primary coil, which receives energy from the ac source. Etc provides this testing as a service to our customers to ensure compatibility between the ballastlamp or driver and our dimming system. 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. Sfra testing on transformers electrical test equipment. Testing of insulating oil requires a oil test vessel in addition to the power factor test set. The vessel, or oil test cell is typically a threeelectrode system which provides guarding against surface leakage.
Major utilities and service companies have used the fra method for more than a decade. Transformer testing commissioning, routine, diagnostic. Mainly two types of transformer testing are done at manufacturer premises type test of transformer and routine test of transformer. Frequently asked sweep frequency response analysis. This paper presents how interpretation of sweep frequency response analysis sfra traces can be done for the open circuit and short circuit winding faults on the 10 kv a power transformer. Condition monitoring of power transformer by using sfra test. 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. Dismantling a power transformer to determine its condition is hardly ever a practical possibility. 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. Sfra testing basics offline test the transformer is seen as a complex impedance circuit open magnetization. Testing of power transformers seems like a similar experience. Power transformer, 25mva, 5523kv, manufactured 1985 by mistake, the transformer was energized with grounded low voltage side after this the transformer was energized again resulting in tripped cb transformer protection worked. Transformers are an electrical component that transmit electrical energy between at least two circuits.
Mrct megger relay and current transformer test set. Basics, maintenance, and diagnostics vii contents continued page 4. The following traces were obtained using the doble sfra software for m5200m5300. The sfra test bases its analysis mainly on having a factory reference test of the transformers, however, in most countries you can find transformers with more than 20 or 40 years in operation, of which there is no with a benchmark test, however, it. Repeat the test for the other phases and the other secondary cores. Imports data from other fra test sets the frax series of sweep frequency response analyzers sfra detects potential mechanical and electrical problems that other methods are unable to detect.
Sfra testing on transformers dismantling a power transformer to determine its condition is hardly ever a practical possibility. According to 3 sfra method determines the transformer responses in a time or frequency area. A 40yearold transformer showed a degree of polymerization of 260 in early 2010 during testing, with estimated remaining life at 19 percent. Routine tests and type tests of transformers electrical4u. 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. Sweep frequency response analysis sfra is made to assess the mechanical integrity of the transformer. 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. Transformer tests eep electrical engineering portal. Type test and routine test of transformer electrical mastar. For safe testing, the test setup must meet the following requirements. Iec6007618 sfra of power transformers, typical test.
Frax99, frax101 and frax150 sweep frequency response. May 10, 20 so transformer ratio test is an essential type test of transformer. Transformer theory quiz questions electrician practice tests. The sfra 5000 offers both high precision and portability in a single package, providing all the accessories required for fast, easy to use, reliable and repeatable measurements. So for ensuring proper performance of electrical power transformer, voltage and turn ratio test of transformer one of the important tests. The core, which makes a path for the magnetic flux. Test connection w 1 synchronous generator 2 test transformer 3 current trans. 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. Mte offers a broad range of products and solutions for the online gasinoil monitoring of transformers online dga. 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. Kirubakaran2 research scholar 1, assistant professor2 abstract ower transformer is one of the most imperative equipments in a high voltage electric power system. Sweep frequency response analyzer sfra quick start guide. The response is measured on the other end of the winding u2f. This is important as the test cell capacitance is small and even small.
Each frequency range corresponds to dfferent components in the transformer. Sweep frequency response analysis test sfra test electrical4u. The test methods used by the authors for presenting the results are described. Transformers regulate the voltage in circuits, but in some cases these can go bad and cause a circuit to not. This guide is based on the operation of the n4l sfra45 sweep frequency response analyzer and will provide a. The purchase, preparation, assembly, operation and maintenance of transformers represent a large expense to the power system.
The transformer the principle parts of a transformer and their functions are. Ltc because in order to change taps, the transformer has to be taken out of service or at least disconnected from the load. The rated power of the transformer relates to a maximum ambient temperature t a max. A sfra open circuit test will show the response of core and windings, while a sfra short circuit test only shows the response of windings. Type tests and special tests are however conducted upon the clients request and depending on agreements. The secondary coil, which receives energy from the primary winding and delivers it to the load. By adjusting cursor positions to frequency subbands, new autocorrelation constants can be calculated. The voltage shall then be reduced to the corresponding specified partial discharge test. The acronym sfra is meaning sweep frequency response analysis. Sweep frequency response analysis sfra proceeds by applying a sinusoidal signal of constant amplitude and variable frequency to one end of the winding under test u1f. Sweep frequency response analysis sfra has become a powerful tool in advanced power transformer assessments and probably one of the main and first tools used to diagnose troubled transformers or as a regular maintenance test. To connect the ground reference cable and test leads and run sfra. By using the latest proven sfra test techniques, it is possible to accurately assess transformer condition without dismantling it. 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.
Mainly two types of transformer are done by manufacturer before dispatching the transformer mainly 1 type test of transformer and 2 routine test. Sweep frequency response analysis sfra is a technique used to externally monitor and assess the condition and mechanical integrity of transformer windings for shortcircuits, opencircuits,deformation, winding insulation breakdown and lose of clamping pressure. The transformer under test must be completely deenergized and isolated from the system. Hence, it is essential to inspect and calibrate those instrument transformers at regular intervals. Scribd is the worlds largest social reading and publishing site. Power transformer winding fault detection based on sfra. The methods used during tests and measurements of the power transformers, test and measurement circuits, calculations and evaluation criterias are included in this manual. This is also true for other, especially mechanical, faults. The results show that on site tests, including high voltage tests, on high voltage power transformers is fully possible and reliable. Magnetic balance test is carried out by applying a low single phase voltage at 50 or 60 hz to each h. Oct 03, 2016 the type and routine test are very important for transformer. As power transformer is highly expensive as well as important part of distribution system.