Sweep frequency response analysis based diagnosis of shorts within transformer windings

Rajamani, Rajesh; Muthaiah, R.; Madanmohan, Balasubramanian

doi:10.1049/iet-gtd.2017.0123

Cited by 18 publications

(16 citation statements)

References 21 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Figure 5.c compares the TF plots at the 4.8 A load level (responses of the transformer under the healthy condition 'NC-4.8 A' and the same faulty conditions, but, at a different load levels 'Sh-2-4.8A' and 'Sh-3-4.8A'. Again, the differences in the transfer function magnitudes indicate that the faults are identifiable and, one faulty case is distinguishable from the other faulty case [7], [11], [17]. The difference in the dB magnitudes at the two different load levels is due to 'combined loading-effect' of the 'inter-turn shortcircuit and the transformer's load' and, demonstrates that the sensitivity of IFRA in inter-turn short-circuit diagnosis is 'load-dependent'.…”

Section: ) Comparisons In Terms Of Statistical Parametersmentioning

confidence: 99%

See 1 more Smart Citation

Influence of the Load on the Impulse Frequency Response Approach Based Diagnosis of Transformer’s Inter-Turn Short-Circuit

2020

Self Cite

View full text Add to dashboard Cite

Frequency Response Analysis (FRA) is an Off-line condition monitoring technique for the transformers and is successful, in diagnosing mechanical faults and inter-turn short-circuits. Only limited literature is available for On-line FRA works, and the effect of the transformer's load on the fault diagnosing capability of FRA has not yet been analysed. Motivated by this research gap, an experimental investigation was done to analyze the effect of load on IFRA based inter-turn short-circuit diagnosis. A single-phase 1 kVA, 240V/240 V transformer supplying R and R-L loads and a three-phase 5 kVA, 440 V/440 V transformer supplying an induction motor at various load levels were tested. Inter-turn short-circuits were emulated in their windings and, the effectiveness of IFRA in diagnosing the same was investigated. Comparisons were made between the frequency response of the loaded transformers in their healthier conditions and emulated fault conditions, based on the transfer function plots and the statistical parameters. Investigations reveal that the loads alter the useful spectrum of IFRA. The frequency response of the healthier transformer itself varies based on the transformer's load and necessitates a careful focus on the sensitive frequency spectra for effective inter-turn short-circuit diagnosis in loaded transformers.

show abstract

Section: ) Comparisons In Terms Of Statistical Parametersmentioning

confidence: 99%

“…where 'V 1 ' is the input impulse signal in volts and 'V 2 ' is the response signal at the other end of the winding in volts [17], [28]. EEV TF plots for all the cases were developed by plotting the 'EEV TF magnitudes' in Y-axis against the 'Frequency 'in X-axis.…”

Section: Procedures Followed For the Analysismentioning

confidence: 99%

Influence of the Load on the Impulse Frequency Response Approach Based Diagnosis of Transformer’s Inter-Turn Short-Circuit

2020

Self Cite

View full text Add to dashboard Cite

show abstract

“…If this is compared with the frequency response of the single air core LV winding, it seems the first pseudo anti-resonant frequency has been shifted to a lower frequency due to the introduction of the magnetizing inductance, and there is no change in the other resonances. The so called 'U' shape at the core dominant low frequency region has been stated in [17,20] as "…in the intermediate frequency band (2)(3)(4)(5)(6)(7)(8)(9)(10)(11)(12)(13)(14)(15)(16)(17)(18)(19)(20), with the apparent absence of the usual first low frequency minima and maxima", and "… is not unique to shell form transformers, being occasionally seen for some core form units, e.g. delta connected HV windings".…”

Section: B Typical Frequency Response Of Single Winding With Magnetimentioning

confidence: 99%

“…The challenge of FRA technique lies in the correct interpretation of the measured FRA spectra. Statistical indices were used to objectively assess the differences in the FRA spectra measured before and after the fault [1,2], as produced by either laboratory experiments [3,4] or simulation studies [5][6][7][8]. Artificial intelligence (AI) was also used to process the FRA data to identify winding faults [9,10].…”

Section: Introductionmentioning

confidence: 99%

Using Lumped Element Equivalent Network Model to Derive Analytical Equations for Interpretation of Transformer Frequency Responses

2020

View full text Add to dashboard Cite

Frequency Response Analysis (FRA) is regarded as the most effective technique for detecting mechanical faults in transformer windings. However, the main challenge in applying the FRA technique lies in the correct interpretation of the differences between the diagnosis and the reference frequency spectra. A transformer can be modelled as an equivalent circuit network comprising inductances (L) and capacitances (C), where L and C are electrical parameters dependent on the winding geometry; a relationship exists between the winding geometry, the electrical components of the equivalent circuit network and the measured FRA spectra. Through electromagnetic circuit analysis, this paper provides a theoretical basis to develop a fundamental understanding of FRA spectra and their resulting interpretation. The FRA spectra are first explained for a single air core winding with uniform structure, and then the complexity is gradually increased by taking into consideration the iron core, the mutual inductive coupling between parts of the same winding and then between the separate windings of the transformer. Mathematical expressions are developed to represent the relationship between the FRA characteristics and the corresponding electrical components of the equivalent circuit network model. INDEX TERMS Transformer Modelling, Frequency Response Analysis (FRA), Interpretation, Electrical Circuit Analysis NOMENCLATURE Real part of permeability of electrical steel in per unit value Imaginary part of permeability of electrical steel in per unit value Winding series capacitance Winding shunt capacitance to ground α Space coefficient Magnetizing inductance of winding Air core inductance of winding Magnetic coupling factor between parts of winding with iron core present Magnetic coupling factor between parts of air core winding Equivalent series capacitance of winding seen from tested winding terminals in a transformer Equivalent winding shunt capacitance to ground seen from tested winding terminals in a transformer n Number of stages/sections in a lumped element equivalent circuit network model Angular frequency N Voltage ratio of high voltage to low voltage windings of transformer

show abstract

“…These tappings (t2, t3, t4 and t5) were accessible through the low capacitive bushings in the sidewalls of the tank. The details were reported in earlier work [33]. The capacitance of the bushings used are, very low (10 pico Coulomb) and hence, they are not affecting the response of the transformer under the test (Impulse) voltage.…”

Section: A Description Of the Test Specimenmentioning

confidence: 99%

Extended Application for the Impulse-Based Frequency Response Analysis: Preliminary Diagnosis of Partial Discharges in Transformer

2020

Self Cite

View full text Add to dashboard Cite

Sweep frequency response analysis based diagnosis of shorts within transformer windings

Cited by 18 publications

References 21 publications

Influence of the Load on the Impulse Frequency Response Approach Based Diagnosis of Transformer’s Inter-Turn Short-Circuit

Influence of the Load on the Impulse Frequency Response Approach Based Diagnosis of Transformer’s Inter-Turn Short-Circuit

Using Lumped Element Equivalent Network Model to Derive Analytical Equations for Interpretation of Transformer Frequency Responses

Extended Application for the Impulse-Based Frequency Response Analysis: Preliminary Diagnosis of Partial Discharges in Transformer

Contact Info

Product

Resources

About