Effects of the Insulation Quality on the Frequency Response of Power Transformers

Abeywickrama, Nilanga; Ekanayake, Chandima; Serdyuk, Yuriy V.; Gubanski, Stanislaw

doi:10.5370/jeet.2006.1.4.534

Cited by 16 publications

(28 citation statements)

References 1 publication

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“…As a result, the FDS method requires larger measuring times to resolve the diagnostic status, whereas the SFRA method can be performed within few minutes. In this context, there is an increasing interest in extending the SFRA method in the process of determining the diagnostic status of winding insulation of a transformer at higher frequencies . In case of any deviation, a detailed FDS‐based analysis may be recommended for further clarification.…”

Section: Introductionmentioning

confidence: 99%

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Theoretical considerations while applying sweep frequency response analysis method in determining the interwinding capacitance of power transformers at higher frequencies

Arumugam

2019

Engineering Reports

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This paper systematically investigates on theoretical and practical aspects of frequency response analysis method in evaluating the dielectric integrity of transformers. Current practices focus on interwinding capacitances as they contain sensitive diagnostic information of transformer windings, magnetic core, and insulation. However, these procedures are inadequate as they are experience based, frequency limited, and overlook the electromagnetic influence of winding core during interwinding capacitance measurements. Corresponding interpretations are subjective and require an expert's decision. Clearly, a method based on trials and involving subjective analysis procedures may render inaccurate and unreliable results. On contrary, if the influence of winding core is minimized, then the high‐frequency cutoff limit can be widened, and the interwinding capacitances can be accurately determined. Presumably, the influence of winding core can be minimized via careful selection of terminal connection, system function pair. For this purpose, resistance‐capacitance and ladder network models describing the impulse behavior of winding‐insulation‐core of transformers are simulated. A suitable terminal connection, system function pair that minimizes the influence of winding‐core is identified. Subsequently, the sensitivity of the proposed method and the accuracy of interwinding capacitance measured are ascertained through comparative analysis and experimentally verified on model coils and transformers. Pertinent interpretations are objective and reveal the sensitive diagnostic information of transformers.

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Section: Introductionmentioning

confidence: 99%

“…Literatures indicate that moisture and pertinent material degradation affects the integrity of winding insulation and, in some cases, causes changes in the interturn and disc‐to‐disc arrangement . Naturally, these deviations could be better observed at both lower and higher frequencies.…”

Section: Introductionmentioning

confidence: 99%

Theoretical considerations while applying sweep frequency response analysis method in determining the interwinding capacitance of power transformers at higher frequencies

Arumugam

2019

Engineering Reports

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“…Reference [13][14][15] presented a study on the effect of moisture and temperature on paper and pressboard between 0.1 mHz and 1 MHz. For both conditions, results show that the real part of complex relative permittivity, ε' has a constant value or flat response from about 1 Hz to 1 MHz.…”

Section: The Effect Of Insulation Condition On Electrical Parametersmentioning

confidence: 99%

Examining the ageing of transformer insulation using FRA and FDS techniques

Yousof

Ekanayake

Saha

2015

IEEE Trans. Dielect. Electr. Insul.

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Frequency response analysis (FRA) is a widely accepted testing technique to assess the mechanical condition of a power transformer. However, it has been reported that FRA is also sensitive to non-mechanical parameters such as the temperature and moisture content of the insulation. Therefore, further studies are required to investigate the ability of FRA on examining the transformer insulation condition. In this paper a study based on an insulation degradation of a single phase 5 kVA model transformer is presented. Throughout the accelerated insulation degradation process, FRA and Frequency Domain Dielectric Spectroscopy (FDS) measurements are performed to analyze the degradation condition. Two methodologies are proposed to analyze the FRA results based on the relative change of capacitance and change of inter-winding capacitance. Results obtained from these approaches are verified with FDS analysis.Index Terms -Power transformers, frequency response analysis, frequency domain spectroscopy, insulation ageing.

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“…This loss peak behaviour shows a significant influence on loss part of dielectric response of oil impregnated pressboard insulation in the frequency range 10 1 -10 3 Hz, particularly for samples with low moisture content. Nilanga et al [238] have identified that this behaviour can be accurately represented with CC function. Thereby, the C-C peak element in the proposed circuit stands for the β relaxation process.…”

Section: Equivalent Circuit For Modelling the Fds Of Pressboard Insulmentioning

confidence: 99%

Condition monitoring of biodegradable oil filled transformer

Mudiyanselage¹,

Bandara²

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Natural and synthetic ester insulating oils have higher fire points and excellent biodegradable characteristics. Therefore, in order to reduce the adverse environmental impact and to improve the fire safety of transformers, there is an increasing demand for natural and synthetic ester insulating liquids as a transformer insulating oil. However, present understanding on ageing behaviour of ester oil-paper composite insulation system and knowledge on application of existing condition monitoring tools for ester based insulation systems are inadequate. This impedes the cost effective and reliable field applications of ester insulating oils, particularly application of natural esters. To reduce this knowledge gap, series of controlled ageing experiments are performed in this research project to provide a better and comprehensive understanding on ageing behaviour of ester oil-paper insulation systems. Furthermore, applicability of existing chemical and electrical based condition monitoring techniques for ester oil-paper insulation systems is systematically investigated in this research project.In this thesis, ageing behaviour of dry pressboard insulation in mineral and three different ester insulating oils under simulated transformer operating environment is investigated. Moreover, the ageing behaviour of natural ester-pressboard composite insulation in moisture rich environment is also compared with that of mineral oil-pressboard system. Degree of polymerisation of pressboard samples measured at different ageing interval is used in this research to determine the ageing condition of pressboard. Moreover, applicability of oil related diagnostic parameters such as concentration of dissolved furanic compounds, acidity value, Dielectric Dissipation Factor (DDF), viscosity and colour to assess the degree of degradation of both ester and mineral insulating oils is thoroughly investigated in this research project. The potential of FTIR (Fourier Transform Infrared spectroscopy) techniques for characterising the degree of degradation of paper insulation is also discussed in this thesis. In addition, this thesis concentrates on characterisation of the charge dynamic in insulating oil through modelling of their dielectric responses.The comparison of gassing behaviour of ester and mineral insulating oils under two different low temperature faults and low energy electric discharge condition is also presented in this thesis.Dissolved Gas Analysis (DGA) results presented in this thesis depicts that faults gases detected in ester and mineral oil samples subjected to a similar fault are akin in type but quantitatively different. The quantity of fault gases produced in two different natural ester oils is also dissimilar.For example, soy-based natural ester produces a large quantity of ethane (C2H6) under low temperature overheating condition than sunflower oil based natural ester. Therefore, this research project investigates the applicability of well-established DGA interpretation schemes namely Duval II | P a g e triangle, IE...

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Effects of the Insulation Quality on the Frequency Response of Power Transformers

Cited by 16 publications

References 1 publication

Theoretical considerations while applying sweep frequency response analysis method in determining the interwinding capacitance of power transformers at higher frequencies

Theoretical considerations while applying sweep frequency response analysis method in determining the interwinding capacitance of power transformers at higher frequencies

Examining the ageing of transformer insulation using FRA and FDS techniques

Condition monitoring of biodegradable oil filled transformer

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