Case studies of factors influencing frequency response analysis measurements and power transformer diagnostics

Reykherdt, Andrew; Davydov, Valery

doi:10.1109/mei.2011.5699444

Cited by 57 publications

(36 citation statements)

References 13 publications

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“…In order to precisely simulate an axial displacement using transformer electrical circuit model, it is crucial to identify the percentage change in the electrical circuit parameters that is equivalent to a particular fault level [31,32]. According to [6,7,33,34], axial displacement will alter the mutual inductance between HV and LV disks windings while the change in capacitive components is to be neglected.…”

Section: Impact Of Axial Displacment On Equivalent Electric Circuit Pmentioning

confidence: 99%

Improved power transformer winding fault detection using FRA diagnostics – part 1: axial displacement simulation

Hashemnia

Abu-Siada

Islam

2015

IEEE Trans. Dielect. Electr. Insul.

139

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Frequency response analysis (FRA) has become a widely accepted tool to detect power transformer winding deformation due to the development of FRA test equipment. Because FRA relies on graphical analysis, interpretation of its signature is a very specialized area that calls for skilled personnel, as so far, there is no reliable standard code for FRA signature identification and quantification. Many researchers investigated the impact of various mechanical winding deformations on the transformer FRA signature using simulation analysis by altering particular electrical parameters of the transformer equivalent electrical circuit. None of them however, investigated the impact of various physical fault levels on the corresponding change in the equivalent circuit parameters. In this paper, the physical geometrical dimension of a single-phase transformer is simulated using 3D finite element analysis to emulate the real transformer operation. A physical axial displacement of different fault levels is simulated in both low voltage and high voltage windings. The impact of each fault level on the electrical parameters of the equivalent circuit is investigated. A key contribution of this paper is the charts it introduces to correlate various axial displacement levels with the percentage change of all transformer equivalent circuit parameters due to the axial displacement fault. In contrary with other researchers who only considered mutual inductance between low voltage and high voltage windings, simulation resultsshown in this paper reveal that other circuit parameters should be changed by a particular percentage to accurately simulate particular fault level of transformer winding axial displacement. Results of this paper aid to precisely simulating winding axial displacement using transformer equivalent circuit that facilitates accurate qualitative and quantitative analysis of transformer FRA signatures.

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Section: Impact Of Axial Displacment On Equivalent Electric Circuit Pmentioning

confidence: 99%

Improved power transformer winding fault detection using FRA diagnostics – part 1: axial displacement simulation

Hashemnia

Abu-Siada

Islam

2015

IEEE Trans. Dielect. Electr. Insul.

139

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“…In addition to mechanical changes of the windings, other factors may also affect the frequency response of a transformer [23]. This may result in a false interpretation, i.e., an external factor influences the frequency response, but it is conceived to be a mechanical change.…”

Section: Influencing Factorsmentioning

confidence: 99%

“…This may result in a false interpretation, i.e., an external factor influences the frequency response, but it is conceived to be a mechanical change. These factors are mainly the temperature, grounding practices, moisture contents, and shunt resistors [23,24]. The best situation occurs when two measurements are carried out in similar conditions, which requires that all of these factors be mentioned in the test sheet.…”

Section: Influencing Factorsmentioning

confidence: 99%

Diagnostic Measurements for Power Transformers

et al. 2016

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Abstract:With the increasing age of the primary equipment of the electrical grids there exists also an increasing need to know its internal condition. For this purpose, off-and online diagnostic methods and systems for power transformers have been developed in recent years. Online monitoring is used continuously during operation and offers possibilities to record the relevant stresses which can affect the lifetime. The evaluation of these data offers the possibility of detecting oncoming faults early. In comparison to this, offline methods require disconnecting the transformer from the electrical grid and are used during planned inspections or when the transformer is already failure suspicious. This contribution presents the status and current trends of different diagnostic techniques of power transformers. It provides significant tutorial elements, backed up by case studies, results and some analysis. The broadness and improvements of the presented diagnostic techniques show that the power transformer is not anymore a black box that does not allow a view into its internal condition. Reliable and accurate condition assessment is possible leading to more efficient maintenance strategies.

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“…Recently however, several literatures have begun to investigate the sensitivity of FRA measurement regarding the transformer insulation condition. Various factors were considered such as the following: 1) Moisture content [3,4].…”

Section: Introductionmentioning

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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Case studies of factors influencing frequency response analysis measurements and power transformer diagnostics

Cited by 57 publications

References 13 publications

Improved power transformer winding fault detection using FRA diagnostics – part 1: axial displacement simulation

Improved power transformer winding fault detection using FRA diagnostics – part 1: axial displacement simulation

Diagnostic Measurements for Power Transformers

Examining the ageing of transformer insulation using FRA and FDS techniques

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