Mechanical stresses in transformer windings

IEEE Trans. Dielect. Electr. Insul.

Islam

2015

Frequency response analysis (FRA) is proven to be a powerful tool to detect winding deformation within power transformers. Although the FRA test along with the equipment are well developed, interpretation of FRA signature is still a challenge and it needs skilled personnel to identify and quantify the fault type if exists as at this stage, there is no reliable standard code for FRA signature classification and quantification. As it is very hard to implement faults on physical transformer without damaging it, researchers investigated the impact of various mechanical winding deformations on the transformer FRA signature by randomly changing the value of particular electrical parameters of the transformer equivalent electrical circuit. None of them however, precisely investigated the correlation between physical fault level and the percentage change in each parameter. In this paper, the physical geometrical dimension of a singlephase transformer is simulated using 3D finite element analysis to emulate the real transformer operation. A physical radial deformation of different fault levels is simulated on both low voltage and high voltage windings. The impact of each fault level on the electrical parameters of the equivalent circuit is investigated and the correlation between the fault level and the percentage change in each parameter of the equivalent circuit is provided. This will facilitate precise fault simulation using transformer equivalent electrical circuit and ease the quantification analysis of FRA signature.

Section: Impact Of Buckling Deformation On Equivalent Electric Circuimentioning

confidence: 99%

Improved power transformer winding fault detection using FRA diagnostics – part 2: radial deformation simulation

Hashemnia

IEEE Trans. Dielect. Electr. Insul.

Islam

2015

“…where H w , D ave , N, I and µ 0 are respectively winding height, average winding diameter, number of turns, RMS winding's current and permeability of air. This force pulls the inner winding close to the core (buckling stress) while pushing the outer winding toward the limb (tensile stress) [27]. Various types of deformations due to radial forces have been discussed in the literature [28].…”

Section: Radial Displacement Fault Considering Harmonicsmentioning

confidence: 99%

Online Transformer Internal Fault Detection Based on Instantaneous Voltage and Current Measurements Considering Impact of Harmonics

Masoum¹,

Hashemnia

IEEE Trans. Power Delivery

et al. 2017

“…Leakage flux and current in the windings causes radial force on windings. This force pulls the inner windings close to the core (buckling stress), while pushing the outer winding toward the limb (tensile stress) [18]. Buckling stress can be simulated in the distributed model by reducing the inter-winding capacitance and the mutual inductance between the windings at the position of deformation.…”

Section: Buckling Stressmentioning

confidence: 99%

Image processing-based on-line technique to detect power transformer winding faults

IECON 2013 - 39th Annual Conference of the IEEE Industrial Electronics Society

Islam

2013

Frequency Response Analysis (FRA) has been growing in popularity in recent times as a tool to detect mechanical deformation within power transformers. To conduct the test, the transformer has to be taken out of service which may cause interruption to the electricity grid. Moreover, because FRA relies on graphical analysis, it calls for an expert person to analyse the results as so far, there is no standard code for FRA interpretation worldwide. In this paper an online technique is introduced to detect the internal faults within a power transformer by constructing the voltage-current (V-I) locus diagram to provide a current state of the transformer health condition. The technique does not call for any special equipment as it uses the existing metering devices attached to any power transformer to monitor the input voltage, output voltage and the input current at the power frequency and hence online monitoring can be realised. Various types of faults have been simulated to assess its impact on the proposed locus. A Matlab code based on digital image processing is developed to calculate any deviation of the V-I locus with respect to the reference one and to identify the type of fault.