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. The sfra traces of this testing would be utilized as base line or previous data. Sfra, detect of winding deformation in power transformer. 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. It is typically used for test specimen that have small capacitance and as a result the power factor tan delta of the test circuit is rather high. Transformers have been used at powerplants since the inception of. 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. Based on the theory of the previous chapter, a value of remanent magnetization was minimal. Smart test set for sweep frequency response analysis sfra on power transformer core and windings. 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. Sweep frequency response analysis with franeo 800 youtube.
Sfra testing basics offline test the transformer is seen as a complex impedance circuit open magnetization impedance 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. The role of sfra is growing in the transformer field and the results interpretation is becoming more and more important day by day. The latest sfra test sets make these techniques more accessible, more convenient and. We can perform sfra test in different ways but mostly used methods are discussed as fallows. Transformers regulate the voltage in circuits, but in some cases these can go bad and cause a circuit to not.
The acronym sfra is meaning sweep frequency response analysis. Sfra testing on transformers electrical test equipment. Detc position should not be altered for an sfra test. 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. Nowadays, there is an increasing interest in sfra method because of its sensibility in detecting mechanical faults without opening the unit. Pdf this paper presents how earth fault damage in the transformer can be detected by sweep frequency response analysis sfra. That time, transformer was out of operation for almost 9 months. Pdf sweep frequency response analysis sfra for the. The sfra traces for the healthy condition of the transformer. A capacitive interwinding measurement describes a test between two. Without the need for a pc to compare transformer fingerprints, the sfra 5000 decreases test time enabling the engineer to. In 2012 the transformer was again subjected to sfra test. Pdf experiences of sweep frequency response analyser for.
Dismantling a power transformer to determine its condition is hardly ever a practical possibility. Sweep frequency response analysis sfra sea trasformatori. If a cable or cable connection is bad, this test will save you hours of wasted effort. The sfra analyzer identifies the following abnormalities in the transformer before they lead to failure.
The technique of sfra is a major advance in transformer condition monitoring analysis. However, for inservice assessment it is considered by some that this method is. The exception is in factory test on a new transformer, where it can be assumed that the detc is in operating condition and tests can be performed on nominal tap. An initial sfra test is carried out to obtain the signature of the transformer frequency. The ac hv test value should not surpass 75% of the factory test value. 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. Sweep frequency response analysis sfra is one of the most powerful diagnostic tools for assessing mechanical damage to a transformer winding.
Doble recommends the default setting of 20 hz 2 mhz for transformers as there is limited diagnostic value in. Ifra and sweep frequencyresponse analysis sfra methods. By using the latest proven sfra test techniques, it is possible to accurately assess transformer condition without dismantling it. Power outages cause loss of income for power consumers and. Every electrical network has a unique frequency response its socalled fingerprint. The test methods used by the authors for presenting the results are described. According to 3 sfra method determines the transformer responses in a time or frequency area. Comparing the time and frequency domain fra test methods is seems to be obvious the sfra, measuring directly in frequency domain, prevailed.
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. 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. Pdf interpretation of sweep frequency response analysis. Main core deformation, open circuits, shorted turns, residual magnetism.
Sweep frequency response analysis of power transformers typical test sequences 525024 issue 1 newtons4th ltd 30 loughborough rd mountsorrel loughborough le12 7at uk tel. It has been developed with the assistance of bureau of reclamation engineers. The transfer function is dependent on the measurement resistance rm which is usually 50. The measurement of sfra can be a part of regular transformer maintenance. If you measure the frequency response of a winding then you can identify winding movement. Therefore the sfra is an increasingly popular test. Sweep frequency response analysis sfra is a method to evaluate the mechanical integrity of.
Sfra, detect of winding deformation in power transformer doi. The sweep frequency response analysis sfra is one of the effective diagnostic tools for detection of winding movement and other mechanical faults which affects the transformer impedance. Type based sfra of one transformer will be compared to an equal type of transformer. This figure shows an m5300, but the connections are correct for all three instruments. Circuit modeling thus needs to accurately represent the behavior of a. Now, transformer was out of operation only for 24 hours. Pdf interpretation of sweep frequency response analysis sfra. 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. Sweep frequency response analysis sfra for the assessment of winding displacements and deformation in power transformers. Sfra is nondestructive test, offline testing and it can be carried out for any voltage rating of power transformer. Sfra testing on transformers dismantling a power transformer to determine its condition is hardly ever a practical possibility. Sweep frequency response analysis sfra as a diagnostic. The latest sfra test sets make these techniques more accessible, more convenient and more dependable that ever.
Frequency response analysis on power transformers omicron. A star connected winding with no neutral star connected windings with no neutral brought out can be treated as a delta winding. Each frequency range corresponds to dfferent components in the transformer. Sfra has been a key tool in the decision to scrap or reenergize a transformer.
Sweep frequency response analysis sfra test on transformer see real results duration. Interpretation of sweep frequency response analysis sfra. Before doing practical simulation of transformer damages, first sfra testing has been carried out on healthy condition of the transformer. Frax99, frax101 and frax150 sweep frequency response.
Sweep frequency response analysis test sfra test electrical4u. Tan delta test loss angle test dissipation factor test. The power transformer of 10 kva has been specially developed inhouse for studying and analyzing sfra traces by practically. Power transformer winding fault detection based on sfra. Diagnostic testing and monitoring of power transformers. Iec 6007618, power transformer, reproducibility, sfra, sweep frequency response. 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. Transformer winding deformation analysis using sfra. Provided the test is done correctly this provides a clear definition for acceptability. To connect the ground reference cable and test leads and run sfra.
Major utilities and service companies have used the fra method for more than a decade. Sweep frequency response analyzer sfra user guide doble engineering company 85 walnut street watertown, massachusetts 024724037 usa. Interpreting sweep frequency response analysis measurements. Sfra is an offline testing and it can be carried out for any voltage rating of. Time based current sfra result will be compared to previous result of the same case. When ac hipot tests are used for routine maintenance, the power transformer can be examined at. This guide is based on the operation of the n4l sfra45 sweep frequency response analyzer and will provide a. Sweep frequency response analysis electrical test equipment. For understanding the shape of the sfra responses it is essential to have a clear idea about the behaviour of the transfer function.
Sweep frequency response analysis test or in short sfra test can detect efficiently, displacement of transformer core, deformation and. The value of fingerprint data is more and more recognized by users all over the world. Sweep frequency response analyzer sfra quick start guide. 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. 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. Lightweight test set for fast and reliable moisture content determination of oilpaper insulated power transformers. 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. Sfra test lead, ground extensions, safety ground, power cord and communication cables. Transformers are an electrical component that transmit electrical energy between at least two circuits. Iec6007618 sfra of power transformers, typical test. Analysis of the results, which are in the form of frequency response traces can, however, be daunting to new users. A very lowfrequency test voltage is applied across the equipment whose insulation to be tested. Sweep frequency response test in the most of the commercial sweep frequency response measuring instruments, the measuring task is.
Use the doble m5400 sweep frequency response analysis test set to investigate mechanical integrity of transformers, reactors and other equipment consisting of windings. 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. Ordering information m5400 range the m5400 provides a frequency response measurement from 10 hz to 25 mhz. Hipot test is typically used for acceptance testing or after transformer repair testing. Condition monitoring of power transformer by using sfra test. Frequency response analysis allows the integrity of the active part of a power transformer to be verified without opening it. The power loss is also a very convenient number when checking the accuracy of measurements. Highly accurate and lightweight test set for current transformer calibration and verification. The cable, winding, current transformer, potential transformer, transformer bushing, on which tan delta test or dissipation factor test to be conducted, is first isolated from the system.
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