Frequency Response Of Transformer Windings Research Articles

Effect of Test Cable Termination on Frequency Response of Transformer Winding

Sweep Frequency Response Analysis (SFRA) method is the most powerful tool to predict the condition of transformer winding. The reliable measurement of frequency response is equally important as its interpretation. A few standards (IEEE std. C57.149-2012, IEC 60076, the Chinese Electrical Power Industry Standard ICS27.100.F24-2005) & much research work have been published, stating dos & don’ts while measuring the frequency response of transformer winding. In this paper, an attempt is made to introduce an additional factor affecting frequency response, while doing measurements. Here, the effect of test cable termination at transformer winding terminals, to prevent signal reflection, on frequency response is presented. A possible way to select suitable value/s of terminating resistance that can correct frequency response is also proposed.

Recent Developments in the Modelling of Transformer Windings

The paper provides a review of the modelling techniques used to simulate the frequency response of transformer windings. The aim of the research and development of modelling methods was to analyze the influence of deformations and faults in the windings on the changes in the frequency response. All described methods are given with examples of the modelling results performed by the authors of this paper and from literature sources. The research is prefaced with a thorough literature review. There are described models based on lumped parameters with input data coming from direct calculations based on the winding geometry and obtained from FEM modelling software and models considering the wave phenomena in the windings. The analysis was also performed for practical problems in winding modelling: the influence of windings other than the modelled one and the influence of parallel wires in a winding.

Modeling frequency response of transformer winding to investigate the influence of RLC

<span>Frequency response measurements are used for power transformer winding failures detection. The variation between frequency responses indicate mechanical changes in the transformer winding. One method to investigate winding failures in transformer is to develop a reliable circuit model which can simulate the frequency response of an actual winding. The main reason to use the model is because it is expensive to create damages on an actual winding. This paper proposes n-stages circuit ladder network to simulate the response of a winding which has unique design. It presents a new technique to calculate the resistance, inductance and capacitance of the winding. Then, the relationship between the RLC parameters and the frequency response is studied. The winding chosen in this investigation is a single phase 33kV transformer winding. The simulated frequency response was compared with the measured response to verify the proposed model. The model can give a comprehensive understanding about the effect of RLC parameters on the frequency response.</span>

The Influence of Capacitance and Inductance Changes on Frequency Response of Transformer Windings

Frequency Response Analysis (FRA) is a test method used for assessment of mechanical condition of transformer active parts. Its biggest problem is the interpretation of test results, namely the relationship between scale of differences between compared curves and the decision for further operation of the given transformer. Very often visible differences between two FRA curves do not mean that there is a deformation in the winding. The cause of the curve shift may come from other elements of the transformer that influence inductive or capacitive parameters. This paper takes under consideration the influence of both capacitance and inductance changes on transformer frequency response (FR). The analysis is performed with the computer model of a transformer and also some experimental results are presented, showing the influence of capacitance and inductance changes on the FR of real transformers. The results of research showed that this influence may lead to misleading effects on the shape of FR characteristics. The paper presents an analysis that can be used in the assessment of FRA measurement, especially in the case of uncertain data comparison results.

Factors influencing the position of the first resonance in the Frequency Response of transformer winding

Factors influencing the position of the first resonance in the Frequency Response of transformer winding

Modeling of frequency response of transformer winding with axial deformations

Abstract One of important methods used for diagnostics of a transformer’s active part is Frequency Response Analysis (FRA). It allows to determine the mechanical condition of windings, their displacements, deformations and electric faults, as well as some problems with internal leads and connections, core and bushings. Still pending problem is interpretation of measurements results. One of approaches is application of computer modeling to simulate various failure modes and connected with them changes in FRA response. The paper presents two types of models, one based on lumped parameters with RLC elements, and one based on distributed parameters with TLM method. Both methods give similar results, comparable to real measurements of simulated coil

Implementation of the SFRA method as valuable tool for detection of power transformer active part deformation

The paper presents the SFRA (Sweep Frequency Response Analysis-SFRA) method for analyzing frequency response of transformer windings in order to identify potential defects in the geometry of the core and winding. The most frequent problems (recognized by SFRA) are: core shift, shorted or open winding, unwanted contact between core and mass, etc. Comparative analysis of this method with conventional methods is carried out in situ transformer in real hard industrial conditions. Benefits of SFRA method are great reliability and repeatability of the measurements. This method belongs to the non-invasive category. Due to the high reliability and repeatability of the measurements it is very suitable for detection of changes in the geometry of the coil and the core during prophylactic field testing, or after transporting the transformer.