Mathematical Comparison Methods to Assess Transfer Functions of Transformers to Detect Different Types of Mechanical Faults

Rahimpour, Ebrahim; Jabbari, M.; Tenbohlen, Stefan

doi:10.1109/tpwrd.2010.2054840

Cited by 130 publications

(70 citation statements)

References 30 publications

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“…In the second group, a numerical index is extracted from the FRA trace measured newly and the fingerprint. The interpretation, then, is carried out based on the values of indices [29][30][31][32][33][34].…”

Section: Interpretation Of Frequency Response Measurementmentioning

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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Section: Interpretation Of Frequency Response Measurementmentioning

confidence: 99%

Diagnostic Measurements for Power Transformers

et al. 2016

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“…A study presented in [41] Movement of the main and top winding 400k to 1M [42] Bulk winding movement between windings and clamping structure 2k to 20k [42] Axial deformations of each single winding > 400k [30] Disc space variation > 100k [43] Radial deformation or movement > 50k [44] > 100k [12] 5k to 500k [30] Shorted turns > 200k [13] < 2k [42] < 10k [30] Axial displacement > 500k [13] > 100k [12,44] Core Core deformation < 2k [42] Magnetic core and circuits < 10k [30] Test leads Variations in grounding practices for test leads > 2M [42] Others Poor grounding condition at site > 500k [41] Ground impedance variation 400k to 1M [42] Residual magnetism < 2k [42] Bushings > 1M [45,46] 24 From various available literatures, a table has been provided which summarizes the sensitivity region of the frequency response according to transformer conditions, this is given in Table 2.5.…”

Section: Frequency Region or Sub-bandmentioning

confidence: 99%

“…This method, however, requires vector fitting algorithm to obtain the transfer function of the transformer frequency response. Rahimpour et al [44] suggested that the correlation coefficient could be applied to reveal the extent of damage by…”

Section: Axial Winding Displacementmentioning

confidence: 99%

“…The result can be normal, slight, obvious or severe deformation. The second is the method proposed in [44] for selecting the failure mode of the winding. It is based on the correlation coefficient which is computed according to the three frequency regions as given in [88].…”

Section: Comparison With Other Interpretation Schemesmentioning

confidence: 99%

“… CC LF CC computed between 1 kHz to 100 kHz  CC MF CC computed between 100 kHz to 600 kHz  CC HF CC computed between 600 kHz to 1 MHz Figure 6.2 Flow chart of the method which was proposed in [44] for determining winding failure mode.…”

Section: Comparison With Other Interpretation Schemesmentioning

confidence: 99%

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Frequency response analysis for transformer winding condition monitoring

Yousof¹,

Fairouz²

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The large power transformer is one of the most expensive assets in a power system network.Special attention needs to be taken to monitor this expensive asset. Among the most critical aspect of a transformer that needs to be monitored is the mechanical condition of the windings and core.One of the best approaches to achieve this is by performing the Frequency Response Analysis (FRA) test on the transformer. The test measures the transfer function response of the transformer winding. If any physical changes occur, it will affect the original response, which can be used to detect any abnormality. However, the critical challenge in this technique is to correctly interpret the measured response in determining the transformer status. Although various investigations have focussed on this issue, the interpretation aspect of FRA is still not fully established.In order to contribute to the improvement of a FRA interpretation scheme, this thesis investigates the sensitivity of FRA measurement on several common winding deformations and explores a new potential diagnostic scheme of FRA. A wide range of power transformers have been used throughout this study ranging from a small sized prototype laboratory transformer to a 30 MVA power transformer installed at a substation.Initially, a mathematical model is established to simulate the frequency response of a power transformer. This is achieved by comparing three models, which are available in the literature.These models are compared in terms of their accuracies to simulate the response and their applicability to studying winding deformation. The comparison shows that the multi-conductor transmission line model is the best approach due to its ability to model each turn of a winding.With the developed model, the sensitivity of the winding response is investigated. This study shows that a minor change to the winding geometrical parameters could cause a considerable change on the response. On a different issue, it is found that a similar winding failure mode may cause a different response variation depending on the winding type. A study based on measurement is also conducted to investigate the influence of windings from other phases to the tested winding. It reveals that the end to end open circuit response is susceptible to the condition of an adjacent winding. Additionally, investigation on the winding response sensitivity due to the tap changer setting is also carried out.This thesis studies several winding deformations, which includes tilting and bending of conductors and inter-disc fault. These three faults are examined in terms of their severity of damage and location of the fault. Statistical analysis is applied to determine the overall condition of the winding. On the other hand, transfer function based analysis is proposed to extract further iii information if the winding is found to be faulty. This includes using the pole plot and Nyquist plot, in which the latter proved to be useful for all winding failure modes. The transfer function is achieved by applying vec...

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Frequency Response Analysis Interpretation for Winding Deformation of Power Transformers

2017

Transformer Ageing

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Mathematical Comparison Methods to Assess Transfer Functions of Transformers to Detect Different Types of Mechanical Faults

Cited by 130 publications

References 30 publications

Diagnostic Measurements for Power Transformers

Diagnostic Measurements for Power Transformers

Frequency response analysis for transformer winding condition monitoring

Frequency Response Analysis Interpretation for Winding Deformation of Power Transformers

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