In 2012 the transformer was again subjected to sfra test. By using the latest proven sfra test techniques, it is possible to accurately assess transformer condition without dismantling it. Pdf power transformer faults identification using sfra. Iec 6007618, power transformer, reproducibility, sfra, sweep frequency response. The transformer the principle parts of a transformer and their functions are. Application of sfra for diagnostics on medical isolation. Pdf interpretation of sweep frequency response analysis sfra. These test templates and application note have been included in the software download since sfra v5. Nowadays, there is an increasing interest in sfra method because of its sensibility in detecting mechanical faults without opening the unit. The m5400 sends an excitation signal into the transformer and measures the returning signals. This paper describes on the sfra connection, theory, sfra results from actual distribution transformer and validation from transformer untanking process to verify any relationship from the sfra results. Frax99, frax101 and frax150 electrical test equipment. 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. For understanding the shape of the sfra responses it is essential to have a clear idea about the behaviour of the transfer function.
Sfra, detect of winding deformation in power transformer doi. Main core deformation, open circuits, shorted turns, residual magnetism. The coreandwindingassembly of power transformers can be seen as a complex. Each frequency range corresponds to dfferent components in the transformer. The following tests are routinely conducted in the field on the transformer.
Sweep frequency response analysis sfra leakage reactance capacitance excitation current core integrity. This test is very reliable for condition monitoring of physical condition of transformer windings. Performing reliable and reproducible frequency response. The latest sfra test sets make these techniques more accessible, more convenient and. 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. Sfra testing on transformers electrical test equipment. Pdf experiences with the practical application of sweep. By adjusting cursor positions to frequency subbands, new autocorrelation constants can be calculated.
However, for inservice assessment it is considered by some that this method is. The primary coil, which receives energy from the ac source. Insulation resistance tests megger test are carried out on all windings, core and core clamping bolts. Sfra is condition monitoring technique for expensive power equipment. The assessment according to all sfra test instrument manufacturers. Anytime a transformer is moved there is a possibility of damage to this transformer. Sfra is an electrical test that provides information relating to transformer mechanical integrity. Sweep frequency response test in the most of the commercial sweep frequency response measuring instruments, the measuring task is.
Once the appropriate bands are selected the ccfs can be evaluated in the context of the individual parts of a transformer. The sfra measurement is done using sweep frequency of 20hz 20mhz applied to transformer of 16mva, 33kv11kv under normal as well as faulty conditions figures uploaded by mariprasath t. 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. Engis sold few units of the sfra and plenty of services with this special tool which helps our clients to detect problems inside the transformer. Highly accurate and lightweight test set for current transformer calibration and verification. The measurements were taken every 20 h during the aging cycle and are displayed in the following colors. Pdf this paper presents how earth fault damage in the transformer can be detected by sweep frequency response analysis sfra. It measures the frequency response of passive element rlc of the apparatus. The winding of transformer may be subjected to mechanical stress.
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. 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. The measurement of sfra can be a part of regular transformer maintenance. What is the megger test procedure for transformers. 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. Based on the theory of the previous chapter, a value of remanent magnetization was minimal. Sweep frequency response analysis electrical test equipment. This guide is based on the operation of the n4l sfra45 sweep frequency response analyzer and will provide a.
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. 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. The transfer function is dependent on the measurement resistance rm which is usually 50. Apply the m5400 during factory tests, after transportation, crane delivery, system faults or even routine maintenance in order to. Close any previous version of the software that is running on your pc. 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. 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. Download as ppt, pdf, txt or read online from scribd. 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. Turn on the sfra test instrument and wait 20 seconds.
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. The standard megger testing equipment is used, the line terminal of which is connected to the winding or core bolt under test. It is important to understand proper test application. The test methods used by the authors for presenting the results are described. Distributor channel partner of transformer test set isa sweep frequency response analyzer sfra 5000, isa t 2000 primary current injection test set, online tan delta measurement test set td guard offered by hitech corporation, vadodara, gujarat. 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. Smart test set for sweep frequency response analysis sfra on power transformer core and windings. Sfra testing on transformers dismantling a power transformer to determine its condition is hardly ever a practical possibility. That time, transformer was out of operation for almost 9 months. Pdf condition monitoring of power transformer by using sfra test. Frequency response transformer testing sfra all about.
If a good reading is found the transformer is good. Assessment of winding deformation in power transformer. According to 3 sfra method determines the transformer responses in a time or frequency area. Any form of physical damage to the transformer results in the changes of this rlc network. It is useful to correlate the two methods to increase the precision of the result. We have developed 10 kv a power transformer to carry out sfra testing. Sfra, detect of winding deformation in power transformer. The secondary coil, which receives energy from the primary winding and delivers it to the load. A capacitive interwinding measurement describes a test between two. It has been developed with the assistance of bureau of reclamation engineers. This is also true for other, especially mechanical, faults. If you measure the frequency response of a winding then you can identify winding movement. 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. Pdf experiences of sweep frequency response analyser for the.
The test in progress and system ok indicator lights go out. The sweep frequency response analysis sfra is an analysis technique for detecting winding displacement and deformation among other mechanical and electrical failures on power and distribution transformers. Condition monitoring of power transformer by using sfra test. Now, transformer was out of operation only for 24 hours. Analysis sfra is a method to assess the mechanical integrity of core and winding of transformer 7. The transformer to be tested must be completely isolated from the power system. The test in progress and system ok indicator lights come on. The m5400 sweep frequency response analyzer adds a powerful tool to your qualitycontrol and maintenance toolkit, allowing you to see inside. Ac voltage is preferable to dc voltage for transformer testing because ac voltage simulates the internal stress that the transformers face during operating conditions. This is a case where a sweep frequency response analysis sfra test will become invaluable. Analysis of transformer by sfra method in measurement of a distribution transformer the frequency scale is set to at least 20 hz to. The core, which makes a path for the magnetic flux. Provided the test is done correctly this provides a clear definition for acceptability. Iec6007618 sfra of power transformers, typical test.
Interpretation of sweep frequency response analysis sfra. Sfra is a comparative method, meaning an evaluation of the transformer. Gopalakrishna professor may 20, 2016 supervisors certificate this is to certify that the work presented in the thesis entitled assessment of winding deformation in power transformer using sfra and numerical techniques submitted by ashwini bhujangrao gaikwad, roll number 214ee4245, is a record of original research. Universal partial discharge pd measurement and analysis system test set for convenient partial discharge localization in power transformers. Doubleclicking results in an incorrect installation that you will have to uninstall later. Pdf the power transformer is one of the most important and expensive. Single phase transformer and applications of single phase transformer. Pdf interpretation of sweep frequency response analysis. To get value from an sfra test it is necessary to make sure that the measurements are credible, which requires good test technique and simple procedures.
Diagnostic testing and monitoring of power transformers. In a power transformer it measures the fault current of the winding over a wide range of frequencies. Sweep frequency response analysis sfra is a tool that can give an indication of core or winding movement in transformers. The following traces were obtained using the doble sfra software for m5200m5300. The transformer is considered to be a complex network of rlc components.
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