Impulse testing of power transformers - a model reference approach
30 Jan 2004-Vol. 151, Iss: 1, pp 25-30
TL;DR: In this article, an objective classification of faults that can occur during impulse tests on power transformers is proposed, including nonlinear elements, breakdown, and partial discharge events, and an analysis of a layer winding, in the time and frequency domains, with these faults shows that current assessment methods must be used with caution.
Abstract: An objective classification of faults that can occur during impulse tests on power transformers is proposed. It includes nonlinear elements, breakdown, and partial discharge events. An analysis of a layer winding, in the time and frequency domains, with these faults shows that current assessment methods must be used with caution. A model reference approach is proposed to distinctly improve recognition in such cases. The method is immune to changes of wave shape and the instant of fault is available by observation.
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TL;DR: In this article, the authors conduct a literature survey and reveal general backgrounds of research and developments in the field of transformer design and optimization for the past 35 years, based on more than 420 published articles, 50 transformer books, and 65 standards.
Abstract: With the fast-paced changing technologies in the power industry, new references addressing new technologies are coming to the market. Based on this fact, there is an urgent need to keep track of international experiences and activities taking place in the field of modern transformer design. The complexity of transformer design demands reliable and rigorous solution methods. A survey of current research reveals the continued interest in application of advanced techniques for transformer design optimization. This paper conducts a literature survey and reveals general backgrounds of research and developments in the field of transformer design and optimization for the past 35 years, based on more than 420 published articles, 50 transformer books, and 65 standards.
159 citations
Cites methods from "Impulse testing of power transforme..."
...A model reference approach for classification of faults that can occur during impulse tests on power transformers is proposed in [363]....
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TL;DR: In this paper, the transfer function (TF) is used to detect different types of mechanical damage in power transformers, such as disc-space variation, radial deformation, and axial displacement.
Abstract: The transfer function (TF) these days is a well-known method to detect different types of mechanical damage in power transformers. The most important mechanical faults mentioned by the authors and researchers, which are most likely to be detected using the TF and occur frequently in transformers, are disc-space variation, radial deformation, and axial displacement. These faults are investigated in this paper using three different similar-size test objects. Since the TF method is a comparative method and the measured results should be compared with the reference results, some mathematical methods are studied to compare different TFs. A complete fault detection, which means determining the type, location, and level of the faults by using TF analyses is the main aim of this paper.
137 citations
Cites background from "Impulse testing of power transforme..."
...By means of this, the type and location of different dielectric faults studied in [37] were distinguished....
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...Breakdown and partial-discharge events have been investigated as an example in [37]....
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TL;DR: The survey provided here is beneficial for the standardization process of these indices and to compare these indices from different aspects to expand the knowledge about their characteristics.
64 citations
TL;DR: In this paper, an objective formulation of the impulse analysis problem from a signal analysis viewpoint is proposed, where the winding response is quintessentially that of a deterministic network to a finite energy signal, with breakdown and partial discharge being inherently nonlinear events.
Abstract: We propose an objective formulation of the impulse analysis problem from a signal analysis viewpoint. The winding response is quintessentially that of a deterministic network to a finite energy signal, with breakdown and partial discharge being inherently nonlinear events. A significant improvement to the acquisition of waveforms is demonstrated by a virtual instrument approach. It retains the advantages of the time- and frequency-domain methods. The drawbacks of the transfer function method are highlighted and a new piecewise linear approach is proposed for analysis. Experiments on a discrete lumped parameter model of the winding are used to validate the PXI based instrument.
30 citations
TL;DR: In this paper, a wavelet network based approach for identification of fault characteristics of dynamic insulation failure during impulse test has been proposed, which identifies the fault characteristics using the significant features extracted from cross-correlation sequence of winding currents of no-fault as well as impulse faulted winding insulation.
Abstract: Wavelet network based approach for identification of fault characteristics of dynamic insulation failure during impulse test has been proposed. The network identifies the fault characteristics using the significant features extracted from cross-correlation sequence of winding currents of no-fault as well as impulse faulted winding insulation. The required winding current waveforms to extract significant features for identification of various fault characteristics are acquired by emulating different dynamic insulation failures in the analog model of 33 kV winding of 3 MVA transformer using developed analog fault simulator. The results show that the wavelet network using cross-correlation features has successfully identified the dynamic insulation failure characteristics, viz. fault type, condition and location of occurrence of failure along the length of the winding with acceptable accuracy. The efficacy of extracted features and developed wavelet network for fault characteristics identification is also compared with artificial neural network classifier. The concept of emulation of dynamic insulation failure, cross-correlation based feature extraction and wavelet based fault characteristics identification methods are explained.
26 citations
Additional excerpts
...transformer insulation during impulse testing [9]....
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References
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Book•
01 Jun 1982
TL;DR: Conduction and breakdown conduction and breakdown in liquid dielectric breakdown in solid dielectrics applications of insulating materials generation of high voltages and currents meaurement of high voltage and currents overvoltage phenomenon and insulation co-ordination in electric power systems non-destructive testing of materials and electrical apparatus high voltage testing of electrical apparatus design, planning and layout of high-voltage laboratories as discussed by the authors.
Abstract: Conduction and breakdown conduction and breakdown in liquid dielectrics breakdown in solid dielectrics applications of insulating materials generation of high voltages and currents meaurement of high voltages and currents overvoltage phenomenon and insulation co-ordination in electric power systems non-destructive testing of materials and electrical apparatus high voltage testing of electrical apparatus design, planning and layout of high voltage laboratories.
694 citations
TL;DR: The transfer function concept is well known as an additional method of evaluating the impulse test of power transformers in the test laboratory and another application for this method is monitoring of power transformer in service as discussed by the authors.
Abstract: Summary form only given as follows. The transfer function concept is well known as an additional method of evaluating the impulse test of power transformers in the test laboratory. Another application for this method is monitoring of power transformers in service. According to the method of how to measure transient signals for the calculation of transfer functions, two kinds of monitoring can be distinguished: off-line and on-line monitoring. Both kinds of monitoring as well as their influencing factors are discussed with on-site measurements on power transformers in service.
175 citations
TL;DR: In this article, the transfer function of a transformer winding is deconvoluted in the frequency domain from the digitally recorded neutral current and high voltage applied during impulse tests, and the integrity of the winding insulation is determined by comparing the transferred function obtained at full and reduced test voltage.
Abstract: The transfer function of a transformer winding is deconvoluted in the frequency domain from the digitally recorded neutral current and high voltage applied during impulse tests. The integrity of the winding insulation is determined by comparing the transfer function obtained at full and reduced test voltage. Differences between the transfer function plots reveal local breakdowns in the winding that can be dissociated from partial discharges. Thus the method permits unambiguous acceptance or rejection if the transformer and, since the transfer function is theoretically immune to changes in the applied impulse, also allows evaluation of the chopped-impulse test. Some 100 windings of large HV power transformers have been tested using the transfer function method, which on several occasions has revealed transformer faults as well a test setup problems that would have been missed or misinterpreted by conventional techniques. >
162 citations
TL;DR: In this article, the authors present a method for calculating terminal and internal impedance versus frequency for a lumped parameter model of a transformer, where the transformer's total frequency response can be accurately determined from this impedance data directly, i.e., the terminal resonance and anti-resonance and internal amplification factor characteristic can be calculated for a single or three-phase transformer model.
Abstract: This paper presents a method for calculating terminal and internal impedance versus frequency for a lumped parameter model of a transformer The transformer's total frequency response can be accurately determined from this impedance data directly, ie, the terminal resonance and anti-resonance and internal amplification factor characteristic can be calculated for a single or three-phase transformer model Since most equipment associated with power system operation can be accurately modeled with lumped parameter networks, this method also provides an accurate, straightforward method for determining the resonance characteristic of those systems An additional significance of this method is that the accuracy of the calculation is limited only by the user's ability to represent the equipment or system Heretofore, the accuracy of this calculation was limited by the simplifying assumptions required of the network model by each solution method This paper presents the definitions and mathematical theory underlying the method Two examples are presented in which comparisons are made between measured and calculated values for a helical air core coil and a 200 MVA single-phase autotransformer The agreement is excellent
149 citations