By adjusting cursor positions to frequency subbands, new autocorrelation constants can be calculated. 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. Dismantling a power transformer to determine its condition is hardly ever a practical possibility. Sfra is an off line testing and it can be carried out for any voltage rating of power transformer, generator transformer and distribution transformer.
Sweep frequency response analyzer sfra user guide doble engineering company 85 walnut street watertown, massachusetts 024724037 usa. Expert system for sweep frequency response analysis of. Details of the sfra test method are given alongside practical results and case studies. The following traces were obtained using the doble sfra software for m5200m5300. Transformer service trafositetesting verify the reliability. The transformer testing performed before commissioning the transformer at the site is called the precommissioning test of the transformer. Sfra is a comparative method, meaning an evaluation of the transformer condition is done by comparing an actual set of sfra results to reference results. This test is carried out on the transformer without opening it and is an off line test.
Sweep frequency response test in the most of the commercial sweep frequency response measuring instruments, the measuring task is. Test your sfra instrument and leads together or test the instrument using the included hook up cables. What is the correct procedure for dvdf and hv test on. It has been developed with the assistance of bureau of reclamation engineers. In this test configuration, input test signal is applied to one end of a winding and the response is measured at one end of another winding on the same phase. Diagnostic testing and monitoring of power transformers. Sfra is condition monitoring technique for expensive power equipment. The following are the methods that are recommended by dielectric systems, inc. Type based sfra of one transformer will be compared to an equal type of transformer.
A transformer is an electrical apparatus designed to convert alternating current from one voltage to another. This is also true for other, especially mechanical, faults. Sweep frequency response analysis sfra for the assessment. Mike horning explains why an sfra test is essential to a transformer maintenance program. Sfra testing on transformers dismantling a power transformer to determine its condition is hardly ever a practical possibility. 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. Doble diagnostic test equipment doble engineering company.
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. Testing of power transformers seems like a similar experience. Sfra and the role it plays in transformer test and maintenance. A change in frequency response as measured by sfra technique indicates a physical change inside the transformer, the cause of which then needs to be identified and investigated. Sfra, sweep frequency response analyzer, power transformers. New sfra measurement interpretation methodology for the. On site oil test for a transformer using sweep frequency. Sweep frequency response analysis electrical test equipment. It is useful to correlate the two methods to increase the precision of the result. 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. Experimental investigations to identify sfra measurement. That time, transformer was out of operation for almost 9 months. Smart test set for sweep frequency response analysis sfra on power transformer core and windings.
Dissolved gas analysis guide for transformers filled with. The latest sfra test sets make these techniques more accessible, more convenient and more dependable that ever. Sfra, detect of winding deformation in power transformer. Mike is a senior transformer advisor and instructor at sdmyers. The test in progress and system ok indicator lights go out.
Sfra, detect of winding deformation in power transformer doi. Sfra testing on transformers electrical test equipment. Timebased current sfra results will be compared to previous results of the same unit. The latest sfra test sets make these techniques more accessible, more convenient and. Magnetic balance test is carried out by applying a low single phase voltage at 50 or 60 hz to each h. 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.
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. A transformer has no moving parts and is a completely. This guide is based on the operation of the n4l sfra45 sweep frequency response analyzer and will provide a. Doble products are recognized for durability and our analytical.
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 made to assess the mechanical integrity of the transformer. Typically, a baseline is taken in the factory to which all subsequent test results are compared. Evaluation of transformer condition using individual and tdcg concentrations. According to 3 sfra method determines the transformer responses in a time or frequency area. In a power transformer it measures the fault current of the winding over a wide range of frequencies. The end results will be a series of ccfs, evaluating different components of the transformer. For understanding the shape of the sfra responses it is essential to have a clear idea about the behaviour of the transfer function. The transformer to be tested must be completely isolated from the power system. All other terminals of the transformer left floating. Sweep frequency response analysis sfra is a powerful and sensitive method to evaluate the mechanical integrity of core, windings and clamping structures within.
The winding of transformer may be subjected to mechanical stresses during transportation, heavy short circuit faults, transient switching. Anytime a transformer is moved there is a possibility of damage to this transformer. 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 opened and sending oil sample to a remote laboratory. Analysis of transformer by sfra method in measurement of a distribution transformer the frequency scale is set to at least 20 hz to. Doble engineering company supports our clients in the electric power industry improve operations and optimize system performance. Sweep frequency response analysis sfra as a diagnostic. 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. Nowadays, there is an increasing interest in sfra method because of its sensibility in detecting mechanical faults without opening the unit. 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. For reasons of range, resolution and repeatability, the sfra technique is shown to be. Transformers while experiencing severity of short circuit current loses its mechanical property by way of deformation of the winding or core. Each frequency range corresponds to dfferent components in the transformer.
The action is carried out by supply a low voltage signal of changeable frequencies to the transformer windings and. Sfra is an electrical test that provides information relating to transformer mechanical integrity. Investigating mechanical integrity in power transformer. This is a case where a sweep frequency response analysis sfra test will become invaluable. 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. 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. Kirubakaran2 research scholar 1, assistant professor2 abstract ower transformer is one of the most imperative equipments in a high voltage electric power system.
Sfra has been a key tool in the decision to scrap or reenergize a transformer. The doble m5150 can be used in the field or in the office allowing you to isolate problems between hardware and cables. The methods used during tests and measurements of the power transformers, test and measurement circuits, calculations and evaluation criterias are included in this manual. The m5400 sends an excitation signal into the transformer and measures the returning signals. Universal partial discharge pd measurement and analysis system test set for convenient partial discharge localization in power transformers. Sometimes it becomes impossible to check the oil level without opening the transformer. Sfra, sweep frequency response analyzer we are proud to introduce a unique equipment, the m5400 sweep frequency response analysis test set to investigate mechanical integrity of transformers, reactors and other equipment consisting of windings. If you measure the frequency response of a winding then you can identify winding movement. It measures the frequency response of passive element rlc of the apparatus. No load losses at 60 hz and 50 hz failure localization shortcircuit impedance.
Iec6007618 sfra of power transformers, typical test. The sfr analyzer identifies the following abnormalities in the. Fra can be divided into two main types, based on the different signals injected into the transformer. Circuit modeling thus needs to accurately represent the behavior of a.
Interpretation of sweep frequency response analysis sfra. The test methods used by the authors for presenting the results are described. 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. V winding in succession and measuring all the other voltages both on high voltage and low voltage side. It can be designed to step up or step down voltages and works on the magnetic induction principle. Turn on the sfra test instrument and wait 20 seconds.
There are several methods of interpreting dissolved gas analysis data in transformers filled with beta fluid. 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. 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. Jan 08, 2019 sfra stands for sweep frequency response analysis. Non typical fault detection in power transformers using sfra. Frequency response transformer testing sfra all about. If the reading is above the amperage rating for the transformer, the circuit is drawing too much power. What is the importance of the sfra test in a transformer.
Time based current sfra result will be compared to previous result of the same case. Overall power factor and capacitance tipup, variable freq 2. Detc position should not be altered for an sfra test. Sanchez proceedings of the world congress on engineering and computer science 2017 vol i wcecs 2017, october 2527, 2017, san francisco, usa. Every electrical network has a unique frequency response its socalled fingerprint. The winding of transformer may be subjected to mechanical stress.
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. Sweep frequency response analysis transformer applications. Shree abirami enggineering works was established in 1992, an iso 9001 2008 certified company is one of the major company in the field of transformer manufacturing, transformer repairing, transformer rewinding, transformer overhauling, transformer erection, transformer testing, transformer rentalhiring, transformer commissioning, transformer servicing, transformer. For example, valves positioned incorrectly, plugged radiators, stuck temperature indicators and level gauges, and noisy oil pumps or fans. The power transformer of 10 kva has been specially developed inhouse for studying and analyzing sfra traces by. Bushings c1, c2, energized collar tipup, variable freq 3. 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 transfer function is dependent on the measurement resistance rm which is usually 50. Our comprehensive high voltage test bay includes kv75kj impulse, ddf, sfra, pd, noise level, temperature rise and harmonics testing, while the routine test bay is equipped to perform tests up to 75mva 2kv. 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. In this paper the method of sweep frequency response analysis sfra has been proposed for on site and instant test of oil condition without requiring the transformer to be opened and sending oil.
Highly accurate and lightweight test set for current transformer calibration and verification. Power transformer faults identification using sfra t. Check relay schemes, evaluate insulation condition and assess risk across your transformer fleet with doble diagnostic test equipment and software. This test configuration is intended to check the response due to the influence of space between two windings in a particular phase. The measurement of sfra can be a part of regular transformer maintenance. In addition to our specialist transformer manufacturing services we also offer overhaul, repair and maintenance services both in. Sfra tests performed on power transformers are shown below, depending on the connection of the windings and the non typical fault detection in power transformers using sfra a. We can perform sfra test in different ways but mostly used methods are discussed as fallows.
The amperage rating for your transformer fuse may be labeled on the transformer, but will also be. The test in progress and system ok indicator lights come on. In 2012 the transformer was again subjected to sfra test. Transformer service trafositetesting verify the reliability of your transformers abb transformer remanufacturing and engineering services tres proudly offers comprehensive onsite transformer testing services with our highvoltage mobile test system.
Main core deformation, open circuits, shorted turns, residual magnetism. 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. Pdf on site oil test for a transformer using sweep. Feb 23, 2012 if a good reading is found the transformer is good. Leakage reactance frequency response of stray losses 7. Basics, maintenance, and diagnostics vii contents continued page 4. Transformer winding deformation analysis using sfra. 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. Based on the theory of the previous chapter, a value of remanent magnetization was minimal. Now, transformer was out of operation only for 24 hours. Mar 29, 2019 test this by hooking up the secondary to its circuit and using your dmm to test the secondary lines. Once the appropriate bands are selected the ccfs can be evaluated in the context of the individual parts of a transformer.
By using the latest proven sfra test techniques, it is possible to accurately assess transformer condition without dismantling it. This highlyaccurate verification device confirms that your equipment is providing you with results you can trust. This test is very reliable for condition monitoring of physical condition of transformer windings. Three methods are commonly used to assess the measured traces. It detects winding defects and faults in the magnetic core thereby helping to improve transformer reliability, reduce maintenance costs and prevent costly failures. The sweep rate response analysis is widely used technique for identify veiled fault and circumstance monitoring of power transformer.
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