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