1Novel method for detection of transformer winding faults using Sweep Frequency Response Analysis Jashandeep Singh Yog Raj Sood Abstract-- Sweep Frequency Response Analysis (SFRA) is an established tool for determining the core deformations, bulk winding movement relative to each other, open circuits and short circuit turns, residual magnetism, deformation within the main transformer winding, axial shift of winding etc. This test is carried out on the transformer without actual opening it and is an off line test. This paper explains the fundamental studies of SFRA measurement on basic electrical circuits, which can be extended for studying the mechanical integrity of a transformer after short circuit fault, transportation etc. Index Terms— SFRA, Power Transformer, Deformation, Impulse response, Resonance frequency. P Winding I. INTRODUCTION ower transformers are one of the most expensive elements in a power system and their failure is a very costly event [4]. Power transformers are mainly involved in the energy transmission and distribution [1]. Unplanned power transformer outages have a considerable economics impact on the operation of electric power network. To have a reliable operation of transformer, it is necessary to identify problems at an early stage before a catastrophic occurs. In spite of corrective & predictive maintenance, the preventive maintenance of power transformer is gaining due importance in modern era and it must be taken into account to obtain the highest reliability of power apparatus like a power transformer. The well known preventive maintenance techniques such as DGA, thermal monitoring, oil analysis, partial discharge measurement, capacitance & tan delta measurements, sweep frequency response analysis, etc. are applied for transformer for a specific type of problem [1, 4]. In the FRA technique, a low amplifier swept frequency signal is applied at the end of one of the transformer windings and the response is measured at the other end of the winding with Jashandeep Singh is Research Scholar in the Department of Electrical Engg. (EED), NIT Hamirpur (H.P), India (
[email protected]) Yog Raj Sood is Prof & Head, Electrical Engg. Department, NIT Hamirpur (H.P), India (
[email protected]) Piuesh Verma is Prof & Head, Electrical & Electronics Engg. Dept, Lovely Institute of Engg.& Technology, Phagwara (Pb.), India (
[email protected]) Raj Kumar Jarial is Lecturer (Selection Grade ), Electrical Engg. Department, NIT Hamirpur (H.P), India 1-4244-1298-6/07/$25.00 ©2007 IEEE. Piush Verma Raj Kumar Jarial one phase at a time. The method is based on the fact that every transformer winding has a unique signature of its transfer function which is sensitive to change in the parameters of the winding, namely resistance, inductance and capacitance. It consist of measuring the impedance of transformer winding over a wide range of frequencies and comparing the results of these measurements with a reference set taken either during installation or at any other point of time. Difference in signature of the responses may indicate damage to the transformer which can be investigated further using other techniques or by an internal examination [9]. II. WINDING DEFORMATION Winding deformation may be due to mechanical and electrical faults. Mechanical faults occur in the form of displaced winding, hoop buckling, winding movement, deformations and damaged winding. They may be due to the loss of pressure, vibration during transportation and also excessive mechanical force during a close-up short circuit fault. Winding movements may also result from stresses induced by electrical faults such as an interturns short circuit as a result of lightning strikes [5, 10, 13]. It may also result in insulation damage. The deformation can also be due to ageing of paper. As a transformer ages the insulation shrink and the clamping pressure may be lost which reduces its voltage withstand strength. Winding deformations in transformers are difficult to establish by conventional methods of diagnostic tests like ratio, impedance/ inductance, magnetizing current etc. Deformation results in relative changes to the internal inductance and capacitance of the winding. These changes can be detected externally by low voltage impulse method or FRA method [4]. III. PURPOSE FOR SFRA MEASUREMENT SFRA measurement is required. • After short circuit testing of Power Transformer. • After Impulse testing of power transformer. • Quality assurance during manufacturing. • Assess Mechanical Condition of Transformers (mechanical distortions). • Detect Core and Winding Movement. • Due to large electromagnetic forces from fault currents. It starts at 0’dB and then shows a characteristics roll off. but equates to infinite dB down. Transformer Relocations or Shipping IV. is that Vout = Vin. shown in Figure 4. CAPACITOR AND RESISTOR Individual passive components. This would be a straight line at -6dB. An ideal resistor reduces the output voltage across the frequency range e. FREQUENCY RESPONSES OF INDUCTOR.g. however. a 50 Ω resistor would give an output voltage half the input voltage. An ideal inductor at low frequency behaves as a short circuit. Vout is referenced via a 50 Ω co-axial cable to ground. and an output voltage of zero. dB = 20 log10 ( Vout ) Vin (1) The output voltage.8 dB as shown in Figure 3. To remove the effect of test leads. as Z=0 Ω .t. The response in dB’s is calculated by the following equation: Response in dB’s. there is no such thing as an ideal inductor. This is shown in Figure 2. The basic measurement circuit is shown in Figure 1. SFRA MEASUREMENT Frequency response analysis plots the ratio of the transmitted voltage waveform to the applied voltage waveform in dB’s.L. This means we have: Vout 50 = Vin 50 + Z Figure 3: Responses of a 50 Ω and a 500 Ω ideal resistor An open circuit would provide infinite impedance. it is the lead length that determines the max effective frequency [18]. This is not calculated as a dB value. Consequently their responses contain elements of each component.matched RF BCN Connector. The signal is measured w. as the resistance of the system goes on increasing. Figure 4: Experimental response of 350 ohm Resistor . The M5200 SFRA Instrument requires a match impedance signal cable. (2) Where Z is frequency dependent impedance function for an Inductor or Capacitor or a combination of the two. adjacent to the test transformer). heading towards an open circuit. the impedance increases. each has elements of the other components. Figure 2: Response of a short circuit Figure 1: Measurement of voltages for SFRA The test leads are made from low loss RG-58 RF coaxial cable with the shield grounded to the instrument chassis through a standard connector. Nevertheless. a three lead system is used to measure both input and output voltages [7]. as the frequency increases. We have tested the 350 Ohm resistance using SFRA. The impedance attenuated the input voltage signal. The expected responses for a short circuit. The length of the lead is 60 ft (This length is the shortest length useful to test the largest transformer from a location on the ground. at any frequency. V.C – have identifiable and distinct frequency responses. It clearly indicates that. the instrument ground. & performs a single end measurement.R. In practice. the dB level of response decreases.2 • • Winding Shrinkage causing release of clamping pressure. its results appears to be around -18db. The shield of the signal cable must be connected to the chassis using 50 ohm impedance.r. on the log scale. a 500 Ω resistor would give a response at -20. an ideal capacitor or an ideal resistor. The response of an ideal inductor is shown in Figure 5. This equals 0 dB across the frequency range. as frequency increases. C. Capacitor only Figure 8: Circuit connection of C only Figure 5: Experimental response of inductor A ideal capacitor behave like an open circuit at low frequencies but at high frequencies it behaves like a short circuit & its response climbs towards zero as frequency rises.3 Signal attenuation. B. (9) (10. 14) 1 w= LC v2 ∴ 20 log ≅ 20 log 0 ≅ −∞ v1 A= (3) (4) D. as indicated in Figure 6 [7. From the circuit. v2 1 α (5) v1 f v2 1 20 log10 α 20 log10 ≅ −20 log f (6) v1 f Figure 10: Circuit connection of series R & L The Signal attenuation of the circuit. 11) Signal attenuation ‘SA’ increases as the frequency is increased and the capacitive reactance is inversely proportional to the frequency. Parallel connection of Capacitors and Inductors Figure 9: Circuit connection of parallel L & C Figure 7: Circuit connection of L only From the circuit. . 11]. ‘SA’ will increase at the rate of 20 dB per decade. THEORETICAL FRA MEASUREMENT ON BASIC ELECTRICAL CIRCUITS A. v2 50 = v1 50 + jwL 50 dB = 20 log10 50 + jwL A= v2 50 (1 − w 2 LC ) = v1 50 (1 − w 2 LC ) + jwL (12. v2 (50 * jwC ) = (7) v1 (50 * jwC ) + 1 (50 * jwC ) dB = 20 log10 (8) (50 * jwC ) + 1 A= At low frequency. SA is inversely proportional to the frequency and the rate of increment of the attenuation is -20 dB per decade. Series connection of Inductors and Resistors At high frequency. 1 f v 2 50 jwC ∴ ≅ αf v1 1 v2 ∴ 20 log10 α 20 log f v1 X Cα Figure 6: Experimental response of capacitor VI. 13. Inductor only The connection diagram for measuring FRA of Inductor is shown in Figure 7. often leading to the creation of new resonant frequencies. This shows that. Poor cable grounds are more difficult to detect. the values of resistances are too small compared to the value of the inductive reactance to produce any changes on the responses in the high frequency region. VII. The lower the resistance.4 A= v2 50 = (15) v1 (50 + jwL + R) The above equation indicates that. the circuit behaves as a voltage divider with the ratio depending on the value of R. the signal attenuation will be like a voltage divider. MODELING TRANSFORMER AS A TWO PORT NETWORKS FOR SFRA MEASUREMENTS Generally. VIII. However. Therefore. if the resistance is high. inductances. such as short-circuited turns. This assures that no external impedance is measured. but are unlikely to lead to the creation of new resonant frequencies [13. When performing SFRA we have an input signal. as it affects all windings. Z12 would equal zero. . in the high-frequency response. the FRA responses produced by the series connection of inductor and resistor are quite similar to the SA results for a single inductor. at low frequency the value of inductance is small enough. As the frequency is increased. Figure 12. the attenuation decreases. Z11. Slight differences are often accepted as being a result of “windings settling into place. Voltage Transfer Function. illustrates a basic two-port network. It is very important to obtain zero impedance between the lower or negative terminals to assure repeatable measurements. A significant decrease normally indicates radial movement of the inner winding (hoop buckling). At the high frequency range. any pair of terminals where a signal may enter or leave an electrical network is described as a port. A transformer undergoing SFRA can thus be modeled by a two-port network. An ungrounded core changes the shunt capacitance of the winding closest to the core and also the low-frequency response. and Z21. 19) In this diagram: • Z12 represents the impedance of the winding and any other electrical paths between the input and output bushings. at high frequencies. referenced to ground.” The high-frequency response is sensitive to faults that cause changes in the properties of parts of the winding. Z12. The transformer tank is common for both negative & lower terminals. are formed by the complex RLC network of the specimen. As the resistance increases. if they are sufficiently large. the attenuation is definitely dominated by the inductive reactance. redirect leakage flux into the core and also change the low-frequency response. The transformer tank & lead ground shields must be connected together to achieve a common-mode measurement. 6]. The inductive reactance increases with the frequency and this will result in further decreasing of the signal attenuation. DIAGNOSING FAULTS The low frequency faults. this is not true if the value of the inductive reactance is larger compared to the value of the resistance. The high-frequency response may also be affected by the tank or cable grounding. A(dB) = 20 log10 ( H ( jw)) A(θ ) = tan −1 ( H ( jw)) (18. However. whereas damage is usually confined to one winding or at worst one phase. and a measured signal. change the magnetizing characteristics of the transformer and hence affect the low-frequency response. Z22. The impedances. It should be noted that the negative terminals are short circuited when transformer are tested. Z12. and Z21 are the open-circuit impedance parameters. for a short circuit. It also reduces the effect of noise. mutual inductances and resistances and are related to the construction and materials of the transformer. Z22. H V ( jw) = Vout ( jw) (17) Vin ( jw) The magnitude and phase is represented as follows [18]. Localized winding damage causes seemingly random changes Figure 12: SFRA Two Port Network Z11. also referenced to ground. Poor tank grounding is easy to spot. the attenuation is dominated by the resistance. the attenuation increases and if the resistance is sufficiently low. Parallel connection of Capacitors and Resistors Figure 11: Circuit connection of parallel R & C A= v2 50 (( R * jwC ) + 1) (50 * R * jwC ) + 50 (16) = = v1 50 (( R * jwC ) + 1) + R (50 * R * jwC ) + 50 + R At low frequency. A significant increase in the medium-frequency resonances normally indicates axial movement of a winding. E. the higher is the ‘SA’. They include capacitances. The medium-frequency response is sensitive to faults that cause a change in the properties of the whole winding. as they may cause changes to just one winding. the capacitance will dominate the response [5]. Circulating currents loops. through the bushing and the winding insulation. ANALYSIS AND INTERPRETATION There is a hierarchy of analysis using SFRA. In an ideal situation. axial shift It is possible to use as the basis for an expert system. Due to the generally small size of Z12 compared to any other paths. this should be ~ 0 It should be clear that if we vary the values of Z11 and Z22. we can rely on three further types of comparison over baseline comparisons: • comparison with a sister unit of the same design • phase to phase comparison of short circuit test results • phase to phase comparison of open circuit test results Comparison with a sister unit has clear benefits in that reference results may be determined for a number of transformers at one time as shown in Figure 13. Figure 14: FRA response under open circuit & short circuit connections X. Figure 14 illustrate the impact of open circuit & short circuit connections in a transformer. Z12 represent not just the winding impedance but also any other impedance paths between the input and output signals. we change the network. however. Any stray impedance may affect the results. Short circuit test results allow direct comparison between phases of a transformer. 16]. there is no substantial impedance between the two bushing flange connections and Z21 approaches zero. Experience has shown. Open Circuits. These should show the classic shape of such a response: near zero dB down at low frequency as the DC resistance of each winding is small. clamping structure Deformation Within the main and tap windings Movement of main and tap winding Leads. Shorted Turns & Residual Magnetism Bulk Winding Movement Relative to Each Other.5 • Z11 and Z22 represent the complex impedance paths to ground. The bands overlap and are not well defined. STANDARD INTERPRETATIONS Experience has shown that different frequency bands of the SFRA trace relate to different elements within a transformer. This is the reason why good grounding is important. that sister units. and an inductive roll off as frequency increases. Open circuit phase-to-phase comparison is only possible in a few circumstances. however. However. Each winding has an expected shape. may show variation: resonance shifts and form changes. by shorting out the LV windings during a HV test. the band limits are not strictly set and vary both . Consequently we must use such results with caution. and why we try to be as consistent as possible in applying grounds to the base of the bushings. there are many causes of variation between phases which means that it is possible to have substantial differences with no problem in the transformer [15]. • Z21 represents the impedance between the two reference grounds. and the results for SFRA may vary. caution must be used. even with successive serial numbers in the factory. But sometime baseline results are not available then. The best method is to compare results to those obtained previously as a baseline. A general overview is given in Table 1 for open circuit measurements. it dominates and Z12 is a close approximation to the winding impedance under most circumstances [8. Any variation between phases should warrant an investigation. Hence we are looking at the response of the three winding arrangements as large inductors. Figure 13: FRA comparison of identical sister unit transformers IX. TABLE I FREQUENCY BANDS AND POSSIBLE SOURCES OF VARIATION Band <2kHz 2kHz to 20kHz 20kHz to 400kHz 400kHz to 2MHz Likely Causes of Variation Core Deformation. This is a very powerful test as. we remove the effect of the core. with some predictable variations. g H1 or A) to another terminal (e. oil level and terminals grounded or shorted. Table 2 to 5. MVA. It is important to note that where previous test results exist. Open Circuit An open circuit measurement is made from one end of a winding to another with all other terminals floating. but even here it may be an indication of a variation of significance [17]. Interwinding measurements are usually considered as optional tests or tests for further investigation when open circuit and short circuit tests are inconclusive (Interwinding tests are marked with an asterisk to indicate their optional nature). When running a test on a transformer winding. For a delta winding. XI. TEST CONNECTIONS Figure 15: Connecting Leads to the Transformer to Measure H1-H0 means that where previous results are available. Test connections are given here for some common transformer designs. measurements must be made in a manner consistent with those previous results.6 with manufacturer and transformer MVA and voltage. for example H1-H0. Good grounds are key to good high frequency responses – make sure ground connections are not hampered by loose connections. This would include. Changing tap position or DETC position or removing core ground connections will give different SFRA results. the red lead is first of the two named terminals.g. as shown in Figure 15. Variation between successive measurements means a change in impedance for the winding and needs to be investigated thoroughly. Reversing these test leads may provide small variations in higher frequency response. shorted or grounded bushings and any particular details for specific tests performed. B. for example. clean. Doble make M5200 SFRA model is capable of doing all needed SFRA test which can be analyzed with SFRA software. It is important to record nameplate and test arrangement data in the 'Nameplate' section of the software. CONNECTIONS OF SFRA Generally. For a star winding measurements are taken from HV terminals to neutral. Doble recommends that the three voltage terminals on the shorted winding are all shorted together. A test lead integrity check may be performed if required. Interwinding An Interwinding measurement is from one winding to another with all other terminals floating. Any neutral connections available for the shorted winding should not be included in the shorting process. for example. The following details are a minimum set required for each test. This would mean. shorting X1 to X2. Hard and fast rules are difficult to generate as there are so many designs and manufacturers. and that good electrical contact is established and maintained. paint or dirt and grease [18]. such as X1 to X0. for example. Short Circuit A short circuit measurement is made with the same SFRA test lead connections as an open circuit measurement but with the difference that another winding is short circuited. Each table gives the recommended tests with position of the red lead and black lead clearly identified. Anything within about 0. • Manufacturer. illustrate all possible combination of SFRA tests for deriving . This ensures all three phases are similarly shorted to give consistent impedance. serial number Make sure good electrical connections are made at bushing terminals and at the base of bushings. H1 to X1 on a double wound transformer or H1 to Y1 on an autotransformer with a tertiary. ensure that you attach the lead grounds to a stud or bolt at the base of the bushing. H2 or N). Variation between phases within a transformer may be the result of design and construction. the best testing procedure is to repeat those tests: taking note of tap position. Impedance • Red and black lead locations • Bushings shorted • LTC and DETC ranges and nominal position • Bushings grounded XII. X2 to X3 and X3 to X1. When connecting leads to a transformer. C. an SFRA measurement is made from one terminal on the transformer (e. It is important to record all relevant information. To ensure repeatability. below a couple of kHz. attach the Red Lead to the H1 bushing and the Black Lead to the H0 bushing. This • LTC and DETC positions during test • Location • HV/LV/TV. With short circuit measurements we are really only looking at low frequencies. MEASUREMENT TYPES A. XIII. Note that H1 to X1 on an autotransformer is not an Interwinding measurement but an open circuit measurement on the series winding. file or wire brush connection points if necessary. connections would be H1 to H3.2 dB is usually considered acceptable. Care must therefore be taken in attaching test leads in the appropriate manner. which includes tap position. Ensure the cables are connected to the test set following the color coded BNC connections. TABLE 2 TWO WINDING TRANSFORMER CONNECTIONS Test Type Test HV Open Circuit (OC) All other terminal floating Test 1 Test 2 Test 3 Test 4 Test 5 Test 6 Test 7 Test 8 Test 9 LV Open Circuit (OC) All other terminal floating Short Circuit (SC) High (H)to Low (L) Short [X1-X2-X3] 3 Phase Δ-Υ H1-H3 H2-H1 H3-H2 X1-X0 X2-X0 X3-X0 H1-H3 H2-H1 H3-H2 3 Phase Υ-Δ H1-H0 H2-H0 H3-H0 X1-X3 X2-X1 X3-X2 H1-H0 H2-H0 H3-H0 3 Phase Δ-Δ H1-H3 H2-H1 H3-H2 X1-X3 X2-X1 X3-X2 H1-H3 H2-H1 H3-H2 3 Phase Υ-Υ H1-H0 H2-H0 H3-H0 X1-X0 X2-X0 X3-X0 H1-H0 H2-H0 H3-H0 1 Phase H1-H2 or (H1-H0) X1-X2 Or (X1-X0) H1-H0 Short [X1X2 or X1-X0] TABLE 3 THREE WINDING TRANSFORMER CONNECTIONS Test Type Test HV Open Circuit (OC) All other terminal floating Test 1 Test 2 Test 3 Test 4 Test 5 Test 6 Test 7 Test 8 Test 9 Test 10 Test 11 Test 12 Test 13 Test 14 Test 15 Test 16 Test 17 Test 18 LV Open Circuit (OC) All other terminal floating Tertiary Open Circuit (OC) All other terminal floating Short Circuit (SC) High (H) to Low (L) Short [X1-X2-X3] Short Circuit (SC) High (H) to Tertiary (T) Short [Y1-Y2-Y3] Short Circuit (SC) Low (L) to Tertiary (T) Short [Y1-Y2-Y3] 3 Phase Δ-Δ-Δ H1-H3 H2-H1 H3-H2 X1-X3 X2-X1 X3-X2 Y1-Y3 Y2-Y1 Y3-Y2 H1-H3 H2-H1 H3-H2 H1-H3 H2-H1 H3-H2 X1-X3 X2-X1 X3-X2 3 Phase Δ-Δ-Υ H1-H3 H2-H1 H3-H2 X1-X3 X2-X1 X3-X2 Y1-Y0 Y2-Y0 Y3-Y0 H1-H3 H2-H1 H3-H2 H1-H3 H2-H1 H3-H2 X1-X3 X2-X1 X3-X2 3 Phase Δ-Υ-Δ H1-H3 H2-H1 H3-H2 X1-X0 X2-X0 X3-X0 Y1-Y3 Y2-Y1 Y3-Y2 H1-H3 H2-H1 H3-H2 H1-H3 H2-H1 H3-H2 X1-X0 X2-X0 X3-X0 3 Phase Δ-Υ-Υ H1-H3 H2-H1 H3-H2 X1-X0 X2-X0 X3-X0 Y1-Y0 Y2-Y0 Y3-Y0 H1-H3 H2-H1 H3-H2 H1-H3 H2-H1 H3-H2 X1-X0 X2-X0 X3-X0 1 Phase H1-H2 or (H1-H0) X1-X2 Or (X1-X0) Y1-Y2 Or (Y1-Y0) H1-H0 Short [X12] H1-H0 Short [Y12] X1-X0 Short [Y12] TABLE 4 THREE WINDING TRANSFORMER CONNECTIONS Test Type Test HV Open Circuit (OC) All other terminal floating Test 1 Test 2 Test 3 Test 4 Test 5 Test 6 Test 7 Test 8 Test 9 Test 10 LV Open Circuit (OC) All other terminal floating Tertiary Open Circuit (OC) All other terminal floating Short Circuit (SC) 3 Phase Υ-Υ-Υ H1-H0 H2-H0 H3-H0 X1-X0 X2-X0 X3-X0 Y1-Y0 Y2-Y0 Y3-Y0 H1-H0 3 Phase Υ -Υ-Δ H1-H0 H2-H0 H3-H0 X1-X0 X2-X0 X3-X0 Y1-Y3 Y2-Y1 Y3-Y2 H1-H0 3 Phase Υ-Δ-Υ H1-H0 H2-H0 H3-H0 X1-X3 X2-X1 X3-X2 Y1-Y0 Y2-Y0 Y3-Y0 H1-H0 3 Phase Υ-Υ-Δ H1-H0 H2-H0 H3-H0 X1-X3 X2-X1 X3-X2 Y1-Y3 Y2-Y1 Y3-Y2 H1-H0 . XIV.7 meaningful analysis related to mechanical integrity of power transformers. L. CONCLUSION In this paper. In nutshell it has been demonstrated that FRA techniques are better than impulse response techniques. L. various basic concepts related to Sweep Frequency Response Analysis (SFRA) are presented in relation to SFRA of various R. C circuits. It has been explained that basic R. C elements responses are helpful for modeling a power transformer which can be considered as a two port network. It has been shown that SFRA responses of different combination of transformer winding can highlight completely the mechanical integrity of power transformer by their careful comparison. January 1992. Noonan. [18] Manual M5200 SFRA.ece. 6. Ryder. pp 1126-1129. April 7-10. Prentice-Hall.D from NIT. Electricity Today Magazine. Hamirpur. 2004.149 And CIGRE WG A2. “ Transformer diagnostics testing by SFRA”.142 Vol.A. “Frequency response analysis approach for condition monitoring of transformer”.1.pdf [17] Tony McGrail. B. Version 1. Tony Mcgrail. His interest researches are Energy management.2.E. Issue June 2001. September 2005. Vaessen and E. From G. Taneja. Vol. Sweetser . Lapworth and T. M. Hamirpur.P. pp 186 – 189. 2002. pp 4-13. 1 S. [14] Lawrence P..C. Benalmadena.edu/~ece2xx/ECE222/Slides/TwoPortsx4. REFERENCES [1] [2] [3] [4] [5] [6] [7] [8] [9] Jorge Pleite. 2005 Doble Engineering Company. Juan Vazquez.0”. A. CEIDP '04. "Transformer Diagnostic Testing by Frequency Response Analysis" IEEE Trans PAS-97. He is working as lecturer in the Electrical Engineering department of NIT. Charles L. 39th International Volume 1. No. Singh.A. pp 3-5. New Jersey. . Boston.M. Transformer Diagnosis and Electrical machines. He did his Diploma in Electrical Engg.Erven. &No.26 On Frequency Response Analysis (FRA) Testing”. Universities Power Engineering Conference. Doble Engineering. IEEE Trans.0”.D. Channakeshava.B. Z. IEEE International Symposium on Electrical Insulation. BIOGRAPHIES Jashan deep Singh was born in Ludhiana (Punjab). D.M. “ A Report on activities By IEEE WG Pc57.Dick. 2004 Annual Report Conference on 17-20 Oct. pp 384-391. Subash C. pp 16 – 22. vol. No. 1984. “Frequency response analysis in diagnosing transformer winding movements fundamental understandings”. pp 2144-2153. On Power Delivery. B. [16] http://www. Wang. [13] P. Ludhiana in 1999. P. 2003 Doble Engineering Co. “Methods for comparing frequency response analysis measurement”. High (H) to Tertiary (T) Short [Y1-Y2-Y3] Short Circuit (SC).Sofian. and M. “SFRA Basic Analysis Vol 1. 1. “Diagnosing transformer faults using frequency response analysis”. Ashok Kumar Yadav. 2004. “SFRA Basic Analysis Vol 2. Charles Sweetser. [11] The Impedance Measurement Handbook”’ 2nd Edition. IEEE MELECON 2006.J.Tech in Instrumentation & Control in 2002 and 2004 respectively.2. B. Tony Mcgrail. Spain. C. Rajkumar. T. Carlos Gonzalez. High (H) to Low (L) Short [X1-X2-X3] Short Circuit (SC). “Mechanical condition assessment of power transformers using frequency response analysis.Tech in Electrical Engg. MA USA.pdx. "Frequency Response Analysis for Diagnostic Testing of Power Transformers".N. Inc.. The Journal of CPRI. Antonio Lazaro. S. 1978. XVI.Ryder. " A New Frequency Response Analysis Method for Power Transformers". 2003 Doble Engineering Co. Version 1.. Electrical Insulation Magazine. Patrick Picher.8 High (H) to Low (L) Short [X1-X2-X3] Short Circuit (SC) High (H) to Tertiary (T) Short [Y1-Y2-Y3] Short Circuit (SC) Low (L) to Tertiary (T) Short [Y1-Y2-Y3] Test 11 Test 12 Test 13 Test 14 Test 15 Test 16 Test 17 Test 18 H2-H0 H3-H0 H1-H0 H2-H0 H3-H0 X1-X0 X2-X0 X3-X0 H2-H0 H3-H0 H1-H0 H2-H0 H3-H0 X1-X0 X2-X0 X3-X0 H2-H0 H3-H0 H1-H0 H2-H0 H3-H0 X1-X3 X2-X1 X3-X2 H2-H0 H3-H0 H1-H0 H2-H0 H3-H0 X1-X3 X2-X1 X3-X2 TABLE 5 AUTO TRANSFORMER CONNECTIONS Test Type Test 3 Phase 1 Phase Series Winding (OC) All other terminal floating Test 1 Test 2 Test 3 Test 4 Test 5 Test 6 Test 7 Test 8 Test 9 Test 10 Test 11 Test 12 Test 13 Test 14 Test 15 Test 16 Test 17 Test 18 H1-X1 H2-X2 H3-X3 X1-H0X0 X2-H0X0 X3-H0X0 Y1-Y3 Y2-Y1 Y3-Y2 H1-H0X0 H2-H0X0 H3-H0X0 H1-H0X0 H2-H0X0 H3-H0X0 X1-H0X0 X2-H0X0 X3-H0X0 H1-X1 Common Winding (OC) All other terminal floating Tertiary Winding (OC) All other terminal floating Short Circuit (SC). Low (L) to Tertiary (T) Short [Y1-Y2-Y3] XV. Simon A.P. Jayasinghe. Hanique. 6-8 Sept.Nirgude. Gunasekaran. Boston. “ Power transformer core fault diagnosis using frequency response analysis”.” 1995 Conference of Doble clients.D. Electrical Insulation and Dielectric Phenomena. Basic Circuit Theory. May 16-19. pp 177-185. India. 2000. [12] J. [15] E. March-April 2003. “Experience with SFRA for Transformer Diagnostics”. Version 1. 2004 pp 138 . 2004. Issue 2. 1995. X1-H0X0 Y1-Y2 (Y1-Y0) H1-H0X0 Short [X1H0X0] H1-H0X0 Short [Y1-Y2] X1-H0X0 Short [Y1-Y2] [10] Simon Ryder. IEEE Volume 19. He is doing his Ph. Agilent Technologies. Huelsman. and 2005 respectively. Presently He is working as Associate Professor in IIT Roorkee. from Indian Institute of Technology. Dr.U.9 Dr. deregulation. Artificial Intelligence Applications to Power System and FACTS. His research interests are in the area of computer applications to power system. He has published a number of research papers. Power System Privatization. Yog Raj Sood obtained his B.D. Unit Commitment. He received his B. Transmission and Distribution network charging. as a Lecturer.D in Electrical engineering with from Thapar Institute of Engineering and Technology (Deemed University). UK under Boyscast Fellowship.D. He has been awarded “The Union Ministry of Energy. Roorkee in 2003. He joined Regional Engineering College Kurukshetra in 1986. India. His field of interest is Power System Economics. Degree(Power Systems Engineering) in the year 1990. power network optimization. high voltage engineering and nonconventional sources of energy. was born in India.E. Presently he is Professor & Head in the Electrical Engineering Department of National Institute of Technology. Hamirpur (H.department of Power Prize” for publication of one of his research paper in the journal of the Institution of Engineers (India). Patiala (India) in 1995 and 2005. University of Bath. India. He has over 15 years of experience in research.P. He has obtained his Ph. He has worked as a Visiting Staff in the Department of Electronics and Electrical Engineering. He received his Master degree with Honors and Ph. Presently he is Professor in the department of Electrical & Electronics Engineering and involved in research in the area of Condition Monitoring of Transformers. in 1984 and 1987 respectively. and received his Degree(Electrical Engineering). Indian Institute of Technology (IIT). Masters Degree(Power Systems Engineering) with Distinction and Ph. in Power System from Punjab Engineering College Chandigarh (U. Chandigarh in 1980. open access transmission system. 1993 and 1997 respectively in India. .E.Sc degree from P.).T.). degree in Electrical Engineering with “Honours” and M.Piush Verma graduated in 1991 with degree in Electrical Engineering from Institution of Engineers (India). Restructuring and Deregulation. 2001. Then he has joined the Department of Electrical Engineering. Assistant Professor and Associate Professor during 1998. Roorkee. industry and academics. Raj Kumar jarial. wheeling.